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  • Impact of Server Failure on Coherence Request Processing

    - by jpurdy
    Requests against a given cache server may be temporarily blocked for several seconds following the failure of other cluster members. This may cause issues for applications that can not tolerate multi-second response times even during failover processing (ignoring for the moment that in practice there are a variety of issues that make such absolute guarantees challenging even when there are no server failures). In general, Coherence is designed around the principle that failures in one member should not affect the rest of the cluster if at all possible. However, it's obvious that if that failed member was managing a piece of state that another member depends on, the second member will need to wait until a new member assumes responsibility for managing that state. This transfer of responsibility is (as of Coherence 3.7) performed by the primary service thread for each cache service. The finest possible granularity for transferring responsibility is a single partition. So the question becomes how to minimize the time spent processing each partition. Here are some optimizations that may reduce this period: Reduce the size of each partition (by increasing the partition count) Increase the number of JVMs across the cluster (increasing the total number of primary service threads) Increase the number of CPUs across the cluster (making sure that each JVM has a CPU core when needed) Re-evaluate the set of configured indexes (as these will need to be rebuilt when a partition moves) Make sure that the backing map is as fast as possible (in most cases this means running on-heap) Make sure that the cluster is running on hardware with fast CPU cores (since the partition processing is single-threaded) As always, proper testing is required to make sure that configuration changes have the desired effect (and also to quantify that effect).

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  • Dealing with numerous, simultaneous sounds in unity

    - by luxchar
    I've written a custom class that creates a fixed number of audio sources. When a new sound is played, it goes through the class, which creates a queue of sounds that will be played during that frame. The sounds that are closer to the camera are given preference. If new sounds arrive in the next frame, I have a complex set of rules that determines how to replace the old ones. Ideally, "big" or "important" sounds should not be replaced by small ones. Sound replacement is necessary since the game can be fast-paced at times, and should try to play new sounds by replacing old ones. Otherwise, there can be "silent" moments when an old sound is about to stop playing and isn't replaced right away by a new sound. The drawback of replacing old sounds right away is that there is a harsh transition from the old sound clip to the new one. But I wonder if I could just remove that management logic altogether, and create audio sources on the fly for new sounds. I could give "important" sounds more priority (closer to 0 in the corresponding property) as opposed to less important ones, and let Unity take care of culling out sound effects that exceed the channel limit. The only drawback is that it requires many heap allocations. I wonder what strategy people use here?

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  • Why does git hash-object return a different hash than openssl sha1?

    - by user657606
    Context: I downloaded a file (Audirvana 0.7.1.zip) from code.google to my Macbook Pro (Mac OS X 10.6.6). (current url: http://code.google.com/p/audirvana/downloads/detail?name=Audirvana%200.7.1.zip&can=2&q= ) I wanted to verify the checksum, which for that particular file is posted as 862456662a11e2f386ff0b24fdabcb4f6c1c446a (SHA-1). git hash-object gave me a different hash, but openssl sha1 returned the expected 862456662a11e2f386ff0b24fdabcb4f6c1c446a. The following experiment seems to rule out any possible download corruption or newline differences and to indicate that there are actually two different algorithms at play: $ echo A > foo.txt $ cat foo.txt A $ git hash-object foo.txt f70f10e4db19068f79bc43844b49f3eece45c4e8 $ openssl sha1 foo.txt SHA1(foo.txt)= 7d157d7c000ae27db146575c08ce30df893d3a64 What's going on?

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  • Visual Studio 2005 - strange characters rendered for ANSI text

    - by Apogee
    Hi all, Has anyone seen this odd text rendering issue in VS2005 before? The first line of using statements actually says "using System;". If I copy the line as it is displayed and paste into notepad, the text appears correctly, so clearly the character codes are correct. In addition, the solution compiles and runs correctly. I was thinking it might be due to ClearCase using a different character encoding as all the solutions we're using were freshly checked-out yesterday on to a new build machine, but this is only happening in 2 of our ~30 solutions. Incidentally the same .cs files when opened in VS2008 render correctly on this machine, could this be a corruption in VS2005?

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  • Regex to *not* match any characters

    - by Erick
    I know it is quite some weird goal here but for a quick and dirty fix for one of our system we do need to not filter any input and let the corruption go into the system. My current regex for this is "\^.*" The problem with that is that it does not match characters as planned ... but for one match it does work. The string that make it not work is ^@jj (basically anything that has ^ ... ). What would be the best way to not match any characters now ? I was thinking of removing the \  but only doing this will transform the "not" into a "start with" ...

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  • Mac OS X 10.5 App "not supported on this architecture" cured by copying?

    - by JWWalker
    I have an app that updates itself over the internet, and the updated copy won't run on PowerPC machines (G5) running Leopard (10.5.8). Double-clicking the app produces a message saying "You can't open the application "appname" because it is not supported on this architecture." But here's the weird part: if I duplicate the app using the Finder or using a cp -R command, then the duplicate runs fine! And yet, if I do ls -laeR on both apps, the results are identical. I restarted the machine, and the difference between the two copies was still there. Sometimes, renaming the app made it run. After a few tries, I managed to rename it back to the original name and still have it run. If this was just on one machine, I'd dismiss it as disk corruption, cosmic rays, or a voodoo hex, but it was reported by a customer and then I reproduced it on my own machine. Any ideas what could cause this behavior?

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  • Storing objects in STL vector - minimal set of methods

    - by osgx
    Hello What is "minimal framework" (necessary methods) of object, which I will store in STL <vector>? For my assumptions: #include <vector> #include <cstring> using namespace std; class Doit { private: char *a; public: Doit(){a=(char*)malloc(10);} ~Doit(){free(a);} }; int main(){ vector<Doit> v(10); } gives *** glibc detected *** ./a.out: double free or corruption (fasttop): 0x0804b008 *** Aborted and in valgrind: malloc/free: 2 allocs, 12 frees, 50 bytes allocated.

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  • When and how does one become a good programmer these days? [closed]

    - by YoungMoney
    I mean, good enough to make software people want and get paid for it. Maybe even good enough to launch a company or something. I'm also concerned that I'm not applying the finer points of my algorithms/data structures/software design knowledge. Background: I'm 20 and have been struggling with programming for about two years now, trying to become a software engineer. I started with a few university courses that I did quite poorly in. I learned how to make websites with HTML/JavaScript and PHP/MySQL, but feel like I know very relevant theory for making good databases - how does something like Facebook serve hundreds of millions of people? What would be smart ways to store data? I don't know. Now I'm doing some android application development, but again I have no idea about good Java design theory (I use static variables like they're going out of fashion) and feel more like I'm gluing stuff together and letting Eclipse slowly autocomplete my project. In short, I'm not sure if I'm becoming a legitimate software developer or just "doing what's cool". At least I've taken some data structures and Algorithms courses and plan to take more in the next years. But I'm having a really tough time applying this stuff to my fun little apps that I'm building. Every language higher level than C++ seems to have its own quicksort function already built-in, for example. Similarly, I can't remember ever needing to implement a linked-list, heap, binary tree, or or worry about pointers and memory management. But maybe this is a good thing so that I focus on other things? I'm not too sure what those other things are though. Hopefully something more than building another photo sharing app. Anyways that's it for me, I look forward to your responses!

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  • WPF: Menu items and combo boxes don't render in Windows 7 64-bit

    - by lilserf
    I'm trying to use an existing internal WPF application (I do have access to the source), but it was developed on XP and I'm using Windows7 64-bit. When I click (for instance) the File menu, 90% of the time I see no drop-down menu at all. The menu still exists - I can use the arrow keys to navigate up and down and choose an option if I happen to know the order of the options, but nothing renders at all. The other 10% of the time, the menu or some portion of it DOES render, but as I move the cursor up and down I get graphical corruption or disappearing options until I end up back at the "no menu is visible at all" state. This is also true of combo boxes within the application - they show no data when I drop them down, but I can arrow down and choose an entry. Microsoft has some advice about WPF rendering issues here but none of these steps has helped with my issue.

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  • Multithreaded SDL error in C++

    - by wyatt
    I'm building a program in C++, using SDL, and am occasionally receiving this error: * glibc detected * ./assistant: double free or corruption (!prev) It's difficult to replicate, so I can't find exactly what's causing it, but I just added a second thread to the program, and neither thread run on its own seems to cause the error. The threads don't share any variables, though they both run the functions SDL_BlitSurface and SDL_Flip. Could running these concurrently throw up such an error, or am I barking up the wrong tree? If this is the cause, should I simply throw a mutex around all SDL calls? Thanks

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  • Why delete and recreate a querydef object when you can just change the .SQL property?

    - by dblE
    Do you remember the venerable old Microsoft Query by Form (QBF) VBA example from back in the day link that recommended that you delete an existing query and then recreate it dynamically?: On Error Resume Next db.QueryDefs.Delete ("qryResults") On Error GoTo 0 Set qdf = db.CreateQueryDef("qryResults", "SELECT p.*... Why not just change the SQL property of the querydef object? qdf.SQL = "SELECT p.*... I am wondering if anyone knows why the MS engineers wrote an example that suggests that you delete and then recreate a query instead of simply changing the SQL property? I would guess that the act of deleting and recreating objects over time could contribute to corruption and bloating in your front end, not to mention changing the SQL property is so much simpler. Does anyone have more insight into this?

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  • Where can these be posted besides the Python Cookbook?

    - by Noctis Skytower
    Whitespace Assembler #! /usr/bin/env python """Assembler.py Compiles a program from "Assembly" folder into "Program" folder. Can be executed directly by double-click or on the command line. Give name of *.WSA file without extension (example: stack_calc).""" ################################################################################ __author__ = 'Stephen "Zero" Chappell <[email protected]>' __date__ = '14 March 2010' __version__ = '$Revision: 3 $' ################################################################################ import string from Interpreter import INS, MNEMONIC ################################################################################ def parse(code): program = [] process_virtual(program, code) process_control(program) return tuple(program) def process_virtual(program, code): for line, text in enumerate(code.split('\n')): if not text or text[0] == '#': continue if text.startswith('part '): parse_part(program, line, text[5:]) elif text.startswith(' '): parse_code(program, line, text[5:]) else: syntax_error(line) def syntax_error(line): raise SyntaxError('Line ' + str(line + 1)) ################################################################################ def process_control(program): parts = get_parts(program) names = dict(pair for pair in zip(parts, generate_index())) correct_control(program, names) def get_parts(program): parts = [] for ins in program: if isinstance(ins, tuple): ins, arg = ins if ins == INS.PART: if arg in parts: raise NameError('Part definition was found twice: ' + arg) parts.append(arg) return parts def generate_index(): index = 1 while True: yield index index *= -1 if index > 0: index += 1 def correct_control(program, names): for index, ins in enumerate(program): if isinstance(ins, tuple): ins, arg = ins if ins in HAS_LABEL: if arg not in names: raise NameError('Part definition was never found: ' + arg) program[index] = (ins, names[arg]) ################################################################################ def parse_part(program, line, text): if not valid_label(text): syntax_error(line) program.append((INS.PART, text)) def valid_label(text): if not between_quotes(text): return False label = text[1:-1] if not valid_name(label): return False return True def between_quotes(text): if len(text) < 3: return False if text.count('"') != 2: return False if text[0] != '"' or text[-1] != '"': return False return True def valid_name(label): valid_characters = string.ascii_letters + string.digits + '_' valid_set = frozenset(valid_characters) label_set = frozenset(label) if len(label_set - valid_set) != 0: return False return True ################################################################################ from Interpreter import HAS_LABEL, Program NO_ARGS = Program.NO_ARGS HAS_ARG = Program.HAS_ARG TWO_WAY = tuple(set(NO_ARGS) & set(HAS_ARG)) ################################################################################ def parse_code(program, line, text): for ins, word in enumerate(MNEMONIC): if text.startswith(word): check_code(program, line, text[len(word):], ins) break else: syntax_error(line) def check_code(program, line, text, ins): if ins in TWO_WAY: if text: number = parse_number(line, text) program.append((ins, number)) else: program.append(ins) elif ins in HAS_LABEL: text = parse_label(line, text) program.append((ins, text)) elif ins in HAS_ARG: number = parse_number(line, text) program.append((ins, number)) elif ins in NO_ARGS: if text: syntax_error(line) program.append(ins) else: syntax_error(line) def parse_label(line, text): if not text or text[0] != ' ': syntax_error(line) text = text[1:] if not valid_label(text): syntax_error(line) return text ################################################################################ def parse_number(line, text): if not valid_number(text): syntax_error(line) return int(text) def valid_number(text): if len(text) < 2: return False if text[0] != ' ': return False text = text[1:] if '+' in text and '-' in text: return False if '+' in text: if text.count('+') != 1: return False if text[0] != '+': return False text = text[1:] if not text: return False if '-' in text: if text.count('-') != 1: return False if text[0] != '-': return False text = text[1:] if not text: return False valid_set = frozenset(string.digits) value_set = frozenset(text) if len(value_set - valid_set) != 0: return False return True ################################################################################ ################################################################################ from Interpreter import partition_number VMC_2_TRI = { (INS.PUSH, True): (0, 0), (INS.COPY, False): (0, 2, 0), (INS.COPY, True): (0, 1, 0), (INS.SWAP, False): (0, 2, 1), (INS.AWAY, False): (0, 2, 2), (INS.AWAY, True): (0, 1, 2), (INS.ADD, False): (1, 0, 0, 0), (INS.SUB, False): (1, 0, 0, 1), (INS.MUL, False): (1, 0, 0, 2), (INS.DIV, False): (1, 0, 1, 0), (INS.MOD, False): (1, 0, 1, 1), (INS.SET, False): (1, 1, 0), (INS.GET, False): (1, 1, 1), (INS.PART, True): (2, 0, 0), (INS.CALL, True): (2, 0, 1), (INS.GOTO, True): (2, 0, 2), (INS.ZERO, True): (2, 1, 0), (INS.LESS, True): (2, 1, 1), (INS.BACK, False): (2, 1, 2), (INS.EXIT, False): (2, 2, 2), (INS.OCHR, False): (1, 2, 0, 0), (INS.OINT, False): (1, 2, 0, 1), (INS.ICHR, False): (1, 2, 1, 0), (INS.IINT, False): (1, 2, 1, 1) } ################################################################################ def to_trinary(program): trinary_code = [] for ins in program: if isinstance(ins, tuple): ins, arg = ins trinary_code.extend(VMC_2_TRI[(ins, True)]) trinary_code.extend(from_number(arg)) else: trinary_code.extend(VMC_2_TRI[(ins, False)]) return tuple(trinary_code) def from_number(arg): code = [int(arg < 0)] if arg: for bit in reversed(list(partition_number(abs(arg), 2))): code.append(bit) return code + [2] return code + [0, 2] to_ws = lambda trinary: ''.join(' \t\n'[index] for index in trinary) def compile_wsa(source): program = parse(source) trinary = to_trinary(program) ws_code = to_ws(trinary) return ws_code ################################################################################ ################################################################################ import os import sys import time import traceback def main(): name, source, command_line, error = get_source() if not error: start = time.clock() try: ws_code = compile_wsa(source) except: print('ERROR: File could not be compiled.\n') traceback.print_exc() error = True else: path = os.path.join('Programs', name + '.ws') try: open(path, 'w').write(ws_code) except IOError as err: print(err) error = True else: div, mod = divmod((time.clock() - start) * 1000, 1) args = int(div), '{:.3}'.format(mod)[1:] print('DONE: Comipled in {}{} ms'.format(*args)) handle_close(error, command_line) def get_source(): if len(sys.argv) > 1: command_line = True name = sys.argv[1] else: command_line = False try: name = input('Source File: ') except: return None, None, False, True print() path = os.path.join('Assembly', name + '.wsa') try: return name, open(path).read(), command_line, False except IOError as err: print(err) return None, None, command_line, True def handle_close(error, command_line): if error: usage = 'Usage: {} <assembly>'.format(os.path.basename(sys.argv[0])) print('\n{}\n{}'.format('-' * len(usage), usage)) if not command_line: time.sleep(10) ################################################################################ if __name__ == '__main__': main() Whitespace Helpers #! /usr/bin/env python """Helpers.py Includes a function to encode Python strings into my WSA format. Has a "PRINT_LINE" function that can be copied to a WSA program. Contains a "PRINT" function and documentation as an explanation.""" ################################################################################ __author__ = 'Stephen "Zero" Chappell <[email protected]>' __date__ = '14 March 2010' __version__ = '$Revision: 1 $' ################################################################################ def encode_string(string, addr): print(' push', addr) print(' push', len(string)) print(' set') addr += 1 for offset, character in enumerate(string): print(' push', addr + offset) print(' push', ord(character)) print(' set') ################################################################################ # Prints a string with newline. # push addr # call "PRINT_LINE" """ part "PRINT_LINE" call "PRINT" push 10 ochr back """ ################################################################################ # def print(array): # if len(array) <= 0: # return # offset = 1 # while len(array) - offset >= 0: # ptr = array.ptr + offset # putch(array[ptr]) # offset += 1 """ part "PRINT" # Line 1-2 copy get less "__PRINT_RET_1" copy get zero "__PRINT_RET_1" # Line 3 push 1 # Line 4 part "__PRINT_LOOP" copy copy 2 get swap sub less "__PRINT_RET_2" # Line 5 copy 1 copy 1 add # Line 6 get ochr # Line 7 push 1 add goto "__PRINT_LOOP" part "__PRINT_RET_2" away part "__PRINT_RET_1" away back """ Whitespace Interpreter #! /usr/bin/env python """Interpreter.py Runs programs in "Programs" and creates *.WSO files when needed. Can be executed directly by double-click or on the command line. If run on command line, add "ASM" flag to dump program assembly.""" ################################################################################ __author__ = 'Stephen "Zero" Chappell <[email protected]>' __date__ = '14 March 2010' __version__ = '$Revision: 4 $' ################################################################################ def test_file(path): disassemble(parse(trinary(load(path))), True) ################################################################################ load = lambda ws: ''.join(c for r in open(ws) for c in r if c in ' \t\n') trinary = lambda ws: tuple(' \t\n'.index(c) for c in ws) ################################################################################ def enum(names): names = names.replace(',', ' ').split() space = dict((reversed(pair) for pair in enumerate(names)), __slots__=()) return type('enum', (object,), space)() INS = enum('''\ PUSH, COPY, SWAP, AWAY, \ ADD, SUB, MUL, DIV, MOD, \ SET, GET, \ PART, CALL, GOTO, ZERO, LESS, BACK, EXIT, \ OCHR, OINT, ICHR, IINT''') ################################################################################ def parse(code): ins = iter(code).__next__ program = [] while True: try: imp = ins() except StopIteration: return tuple(program) if imp == 0: # [Space] parse_stack(ins, program) elif imp == 1: # [Tab] imp = ins() if imp == 0: # [Tab][Space] parse_math(ins, program) elif imp == 1: # [Tab][Tab] parse_heap(ins, program) else: # [Tab][Line] parse_io(ins, program) else: # [Line] parse_flow(ins, program) def parse_number(ins): sign = ins() if sign == 2: raise StopIteration() buffer = '' code = ins() if code == 2: raise StopIteration() while code != 2: buffer += str(code) code = ins() if sign == 1: return int(buffer, 2) * -1 return int(buffer, 2) ################################################################################ def parse_stack(ins, program): code = ins() if code == 0: # [Space] number = parse_number(ins) program.append((INS.PUSH, number)) elif code == 1: # [Tab] code = ins() number = parse_number(ins) if code == 0: # [Tab][Space] program.append((INS.COPY, number)) elif code == 1: # [Tab][Tab] raise StopIteration() else: # [Tab][Line] program.append((INS.AWAY, number)) else: # [Line] code = ins() if code == 0: # [Line][Space] program.append(INS.COPY) elif code == 1: # [Line][Tab] program.append(INS.SWAP) else: # [Line][Line] program.append(INS.AWAY) def parse_math(ins, program): code = ins() if code == 0: # [Space] code = ins() if code == 0: # [Space][Space] program.append(INS.ADD) elif code == 1: # [Space][Tab] program.append(INS.SUB) else: # [Space][Line] program.append(INS.MUL) elif code == 1: # [Tab] code = ins() if code == 0: # [Tab][Space] program.append(INS.DIV) elif code == 1: # [Tab][Tab] program.append(INS.MOD) else: # [Tab][Line] raise StopIteration() else: # [Line] raise StopIteration() def parse_heap(ins, program): code = ins() if code == 0: # [Space] program.append(INS.SET) elif code == 1: # [Tab] program.append(INS.GET) else: # [Line] raise StopIteration() def parse_io(ins, program): code = ins() if code == 0: # [Space] code = ins() if code == 0: # [Space][Space] program.append(INS.OCHR) elif code == 1: # [Space][Tab] program.append(INS.OINT) else: # [Space][Line] raise StopIteration() elif code == 1: # [Tab] code = ins() if code == 0: # [Tab][Space] program.append(INS.ICHR) elif code == 1: # [Tab][Tab] program.append(INS.IINT) else: # [Tab][Line] raise StopIteration() else: # [Line] raise StopIteration() def parse_flow(ins, program): code = ins() if code == 0: # [Space] code = ins() label = parse_number(ins) if code == 0: # [Space][Space] program.append((INS.PART, label)) elif code == 1: # [Space][Tab] program.append((INS.CALL, label)) else: # [Space][Line] program.append((INS.GOTO, label)) elif code == 1: # [Tab] code = ins() if code == 0: # [Tab][Space] label = parse_number(ins) program.append((INS.ZERO, label)) elif code == 1: # [Tab][Tab] label = parse_number(ins) program.append((INS.LESS, label)) else: # [Tab][Line] program.append(INS.BACK) else: # [Line] code = ins() if code == 2: # [Line][Line] program.append(INS.EXIT) else: # [Line][Space] or [Line][Tab] raise StopIteration() ################################################################################ MNEMONIC = '\ push copy swap away add sub mul div mod set get part \ call goto zero less back exit ochr oint ichr iint'.split() HAS_ARG = [getattr(INS, name) for name in 'PUSH COPY AWAY PART CALL GOTO ZERO LESS'.split()] HAS_LABEL = [getattr(INS, name) for name in 'PART CALL GOTO ZERO LESS'.split()] def disassemble(program, names=False): if names: names = create_names(program) for ins in program: if isinstance(ins, tuple): ins, arg = ins assert ins in HAS_ARG has_arg = True else: assert INS.PUSH <= ins <= INS.IINT has_arg = False if ins == INS.PART: if names: print(MNEMONIC[ins], '"' + names[arg] + '"') else: print(MNEMONIC[ins], arg) elif has_arg and ins in HAS_ARG: if ins in HAS_LABEL and names: assert arg in names print(' ' + MNEMONIC[ins], '"' + names[arg] + '"') else: print(' ' + MNEMONIC[ins], arg) else: print(' ' + MNEMONIC[ins]) ################################################################################ def create_names(program): names = {} number = 1 for ins in program: if isinstance(ins, tuple) and ins[0] == INS.PART: label = ins[1] assert label not in names names[label] = number_to_name(number) number += 1 return names def number_to_name(number): name = '' for offset in reversed(list(partition_number(number, 27))): if offset: name += chr(ord('A') + offset - 1) else: name += '_' return name def partition_number(number, base): div, mod = divmod(number, base) yield mod while div: div, mod = divmod(div, base) yield mod ################################################################################ CODE = (' \t\n', ' \n ', ' \t \t\n', ' \n\t', ' \n\n', ' \t\n \t\n', '\t ', '\t \t', '\t \n', '\t \t ', '\t \t\t', '\t\t ', '\t\t\t', '\n \t\n', '\n \t \t\n', '\n \n \t\n', '\n\t \t\n', '\n\t\t \t\n', '\n\t\n', '\n\n\n', '\t\n ', '\t\n \t', '\t\n\t ', '\t\n\t\t') EXAMPLE = ''.join(CODE) ################################################################################ NOTES = '''\ STACK ===== push number copy copy number swap away away number MATH ==== add sub mul div mod HEAP ==== set get FLOW ==== part label call label goto label zero label less label back exit I/O === ochr oint ichr iint''' ################################################################################ ################################################################################ class Stack: def __init__(self): self.__data = [] # Stack Operators def push(self, number): self.__data.append(number) def copy(self, number=None): if number is None: self.__data.append(self.__data[-1]) else: size = len(self.__data) index = size - number - 1 assert 0 <= index < size self.__data.append(self.__data[index]) def swap(self): self.__data[-2], self.__data[-1] = self.__data[-1], self.__data[-2] def away(self, number=None): if number is None: self.__data.pop() else: size = len(self.__data) index = size - number - 1 assert 0 <= index < size del self.__data[index:-1] # Math Operators def add(self): suffix = self.__data.pop() prefix = self.__data.pop() self.__data.append(prefix + suffix) def sub(self): suffix = self.__data.pop() prefix = self.__data.pop() self.__data.append(prefix - suffix) def mul(self): suffix = self.__data.pop() prefix = self.__data.pop() self.__data.append(prefix * suffix) def div(self): suffix = self.__data.pop() prefix = self.__data.pop() self.__data.append(prefix // suffix) def mod(self): suffix = self.__data.pop() prefix = self.__data.pop() self.__data.append(prefix % suffix) # Program Operator def pop(self): return self.__data.pop() ################################################################################ class Heap: def __init__(self): self.__data = {} def set_(self, addr, item): if item: self.__data[addr] = item elif addr in self.__data: del self.__data[addr] def get_(self, addr): return self.__data.get(addr, 0) ################################################################################ import os import zlib import msvcrt import pickle import string class CleanExit(Exception): pass NOP = lambda arg: None DEBUG_WHITESPACE = False ################################################################################ class Program: NO_ARGS = INS.COPY, INS.SWAP, INS.AWAY, INS.ADD, \ INS.SUB, INS.MUL, INS.DIV, INS.MOD, \ INS.SET, INS.GET, INS.BACK, INS.EXIT, \ INS.OCHR, INS.OINT, INS.ICHR, INS.IINT HAS_ARG = INS.PUSH, INS.COPY, INS.AWAY, INS.PART, \ INS.CALL, INS.GOTO, INS.ZERO, INS.LESS def __init__(self, code): self.__data = code self.__validate() self.__build_jump() self.__check_jump() self.__setup_exec() def __setup_exec(self): self.__iptr = 0 self.__stck = stack = Stack() self.__heap = Heap() self.__cast = [] self.__meth = (stack.push, stack.copy, stack.swap, stack.away, stack.add, stack.sub, stack.mul, stack.div, stack.mod, self.__set, self.__get, NOP, self.__call, self.__goto, self.__zero, self.__less, self.__back, self.__exit, self.__ochr, self.__oint, self.__ichr, self.__iint) def step(self): ins = self.__data[self.__iptr] self.__iptr += 1 if isinstance(ins, tuple): self.__meth[ins[0]](ins[1]) else: self.__meth[ins]() def run(self): while True: ins = self.__data[self.__iptr] self.__iptr += 1 if isinstance(ins, tuple): self.__meth[ins[0]](ins[1]) else: self.__meth[ins]() def __oint(self): for digit in str(self.__stck.pop()): msvcrt.putwch(digit) def __ichr(self): addr = self.__stck.pop() # Input Routine while msvcrt.kbhit(): msvcrt.getwch() while True: char = msvcrt.getwch() if char in '\x00\xE0': msvcrt.getwch() elif char in string.printable: char = char.replace('\r', '\n') msvcrt.putwch(char) break item = ord(char) # Storing Number self.__heap.set_(addr, item) def __iint(self): addr = self.__stck.pop() # Input Routine while msvcrt.kbhit(): msvcrt.getwch() buff = '' char = msvcrt.getwch() while char != '\r' or not buff: if char in '\x00\xE0': msvcrt.getwch() elif char in '+-' and not buff: msvcrt.putwch(char) buff += char elif '0' <= char <= '9': msvcrt.putwch(char) buff += char elif char == '\b': if buff: buff = buff[:-1] msvcrt.putwch(char) msvcrt.putwch(' ') msvcrt.putwch(char) char = msvcrt.getwch() msvcrt.putwch(char) msvcrt.putwch('\n') item = int(buff) # Storing Number self.__heap.set_(addr, item) def __goto(self, label): self.__iptr = self.__jump[label] def __zero(self, label): if self.__stck.pop() == 0: self.__iptr = self.__jump[label] def __less(self, label): if self.__stck.pop() < 0: self.__iptr = self.__jump[label] def __exit(self): self.__setup_exec() raise CleanExit() def __set(self): item = self.__stck.pop() addr = self.__stck.po

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  • top tweets WebLogic Partner Community – June 2012

    - by JuergenKress
    Send your tweets @wlscommunity #WebLogicCommunity and follow us at http://twitter.com/wlscommunity OTNArchBeat? Free Virtual Developer Day: Oracle ADF and Oracle Fusion Middleware Development http://bit.ly/MxuNAg AMIS, Oracle & Java? Checklist veearts nu ook op iPad. @amis_services Mobile integratie met Oracle Fusion Middleware http://dld.bz/buwsM #OSB #SOA WhitehorsesWhiteblog: Troubleshoot JVM crashes of Weblogic: CompilerThread (http://bit.ly/KcGzZK) Jon petter hjulstad E-vita is now Apps Grid Specialized! ODTUG Fusion Middleware Sessions RT @OTNArchBeat: ODTUG Kscope12 - June 24-28 - San Antonio, TX http://bit.ly/LlWkNV OTNArchBeat? Free Event: Modern #Java Development, in/outside the Enterprise - May 30 - Redwood Shores, CA http://bit.ly/LfB79a ADF Community DE? Oracle Advanced ADF 11g Partner Workshop Düsseldorf /Germany (english) June 26-29, click here to see Nicolas Lorain? Best Practices for #JavaFX 2 Enterprise Applications (Part Two) http://buff.ly/Lk1DBn by Jim Weaver shay shmeltzer? #Oracle Developers in #Israel - don't miss the free #ADF workshop July 2nd - get hands-on with Oracle ADF -here OTNArchBeat? Java at JAXconf | Tori Wieldt http://bit.ly/LdoLS2 Anand Akela? #Oracle Customers and Partners – Get your free pass to @CloudExpo in New York, June 11 to 14, http://goo.gl/RpYFT <- Stop by booth #511 OracleSupport_WLS? Did you know that since 3/15/12 #WebLogic Server 12.1.1.0 is certified for production with JDK 7? http://bit.ly/IYJE0L Sharat? Highly useful #JavaFX best practices blog by @JavaFXpert More details here ADF EMG How to set up a productive ADF Dev Env - discussion started by @baigsorcl. Click here to Read and comment. OracleSupport_WLS Upcoming #webcast: Diagnosing #weblogic performance issues through #java thread dumps http://bit.ly/M4O9qF My Oracle Support? New to Oracle Support? - Webcast on Support Basics webcast May 22 10:30 Central Europe. Register @ http://bit.ly/J8o0WG Mohamad Afshar? Cloud Expo – Oracle Customers and Partners – get your free pass to Cloud Expo in New York, June 11 to 14, http://goo.gl/RpYFT OTNArchBeat Oracle VM 3.1 is here | @Ronenkofman http://bit.ly/JriWTq Oracle Exalogic? RT @D0uglasPhillips: ExalogicTV New Video Introducing Oracle Secure Global Desktop for #Exalogic!! http://bit.ly/nwkrCu OracleBlogs? Java EE6 and WebLogic YouTube video channels http://ow.ly/1jVcYJ Oracle WebLogic RT @aleftik: Excited to spend some time today playing around with the WebSockets SDK http://bit.ly/NoTtri WebLogic Community Java EE6 and WebLogic YouTube video channels http://wp.me/p1LMIb-h0 OracleSupport_WLS New tutorial! How to use the #JMS #API to create a message producer with #GlassFish and #NetBeans http://bit.ly/Juqjn JDeveloper & ADF? Tip when installing JDeveloper 11.1.2.2.0 version http://dlvr.it/1b48s1 WebLogic Community Middleware Oracle Excellence Awards 2012 – HAPPY NEW YEAR! Click here to read WebLogicCommunity #opn #oracle#Specialization #opnaward Steven Davelaar? Improve performance of your ADF app using lazy, on-demand querying of detail view objects: Click here OracleBlogs? Middleware Oracle Excellence Awards 2012 & HAPPY NEW YEAR! http://ow.ly/1kahzZ OracleSupport_WLS Upgrading from #weblogic 9.2.x to 10.3.x? http://bit.ly/Kqzl9N AMIS, Oracle & Java “@JDeveloper: Logout from an ADF application http://dlvr.it/1fQBnm” WebLogic Community UK OUG call for papers–your middleware success! Click here #UKOUG #soacommunity #OPN Whitehorses Whiteblog: Enterprise Manager: Manage your Fusion Middleware logfiles (http://bit.ly/KQlZkR) WebLogic Community? @Jphjulstad HI Jon, should we send Pizza when you go in production with your WebLogic 12c project? Whish you success! #WebLogicCommunity Sabine Leitner ADF Einsteigerworkshops je 2 Tage im Juni in HAM, BLN, HANN #Oracle #WLS http://bit.ly/LcOIzB @OracleWebLogic @OracleAppGrid@soacommunity Andreas Koop new post Java Heap Monitor in JDeveloper http://bit.ly/LgSk85 Sabine Leitner? #Oracle Kundentag mit Vorträgen von Sparkasse, Schufa, LBBW, Allianz über FMW & Exa Lösungen! 21.06. FRA http://bit.ly/JtwE3v @wlscommunity NetBeans Team RT @chadlung: Installing and configuring #NetBeans 7.1.2 and the #Java JDK 1.7 on OS X: http://www.giantflyingsaucer.com/blog/p=3760 #osx WebLogic Community Happy New Year #WeblogicCommunity thanks for the business! Time for a drink http://pic.twitter.com/K34KFbvH WebLogic Community UK OUG call for papers&ndash;your middleware success! http://wp.me/p1LMIb-gU WebLogic Community? Middleware Oracle Excellence Awards 2012 - HAPPY NEW YEAR! http://wp.me/p1LMIb-h6 Oracle WebLogic? RT @wlscommunity: WebLogic World Record Two Processor Result with SPECjEnterprise2010 Benchmark Click here to read #weblogic #sunfire #li Marc? Relocate wlst script for all the logfiles in your domain @wlscommunity, http://tinyurl.com/btbjcco WebLogic Community WebLogic World Record Two Processor Result with SPECjEnterprise2010 Benchmark Click here #WebLogicCommunity #weblogic #sunfire Oracle WebLogic MIss a WebLogic Devcast webinar? Catch any of the replays in the series on-demand! #WebLogic #JavaEE #coherence http://bit.ly/LNGa4p JDeveloper & ADF? Bean DataControl - Edit table records http://dlvr.it/1ZWqCx Justin Kestelyn? Contents of "Virtual Developer Day: Java SE 7 and JavaFX 2.0" are now avail on demand; no reg http://tinyurl.com/78nxnyo Frank Nimphius? Preparing 12c new features for DOAG 2012 Development - June 14th in Bonn (http://development.doag.org) WebLogic Community? Middleware Oracle Excellence Awards 2012&ndash;HAPPY NEW YEAR! http://wp.me/p1LMIb-he JDeveloper & ADF Placeholder Watermarks with ADF 11.1.2 http://dlvr.it/1ZWDc9 Oracle ACE Program? May edition #ACE newsletter now available online. http://bit.ly/LKA2de chriscmuir New blog post: Which JDeveloper is right for me? http://bit.ly/J8sj9e GlassFish? Transactional Interceptors in Java EE 7 - Request for feedback: Linda described how EJB's container-managed tr http://bit.ly/KKuGNJ OracleEnterpriseMgr Oracle Application Testing Suite 12.1 Debuts at StarEast 2012 http://ow.ly/aXcv8 #em12c JAX London First set of speaker session announced for #JAXLondon see: http://bit.ly/L0HSME OTNArchBeat? Oracle Cloud Conference: dates and locations worldwide http://bit.ly/JgNeID NetBeans Team? Video: Create and debug a TestNG test class in #NetBeans IDE: http://ow.ly/b7NEW NetBeans Team #NetBeans tip: Code Template for #Kohana #PHP Framework: http://ow.ly/aWIvY Robin? Started to use the #Oracle #WebLogic Server #Maven Plugin. Really awesome to install a complete #WLS with "mvn wls:install" !@wlscommunity OTNArchBeat? Free Event: Modern #Java Development, in/outside the Enterprise - May 30 - Redwood Shores, CA http://bit.ly/JIN9tf OracleBlogs WebLogic Partner Community Newsletter May 2012 http://ow.ly/1k5TeG Java Certification? Java SE 7 Fundamentals course now available On Demand. Watch a preview now: http://ow.ly/aWYgD Whitehorses Whiteblog: Native IO in WebLogic on Solaris 11 X64 (http://bit.ly/KGM4mp) NetBeans Team? Quick video of FindBugs Integration in #NetBeans IDE 7.2: http://ow.ly/aNece NetBeans Team #JavaFX Scene Builder Docs Updated for 2.2 and #NetBeans 7.2 dev builds: http://ow.ly/b7Nie Duncan Mills? New blog posting on implementing input field watermarks with ADF Faces 11.1.2 Click here #adf WebLogic Community? WebLogic Partner Community Newsletter May 2012 http://wp.me/p1LMIb-h4 OracleBlogs? UK OUG call for papersyour middleware success! http://ow.ly/1jNs49 Nicolas Lorain? Java tip: Deploying #JavaFX apps to multiple environments - JavaWorld http://buff.ly/KDADvu Adam Bien? Java EE and How to Specify The Unconventional With Convention Over Configuration [Free Article]: The free http://bit.ly/JEUkUf Owen Hughes and team?#Oracle #Exalogic #Performance: What? How? Why? Click here GlassFish? SecuritEE in the Cloud: Java EE 7 and the Cloud theme continue to move full steam ahead. In a PaaS environment http://bit.ly/K2RPte JDeveloper & ADF? How to Align Managed Bean Scope and Bean Data Control in Oracle ADF http://dlvr.it/1dngxQ Andrejus Baranovskis Missing New Feature in JDev (11.1.2.2.0) - ADF Methods Security http://fb.me/1jQM1enls OracleSupport_WLS? Tutorial on managing #HTTP Sessions in a #Weblogic #Cluster http://bit.ly/JshESe Oracle WebLogic? ZeroTurnaround developer report: #Spring keeps getting heavier, and #Java EE keeps getting lighter http://bit.ly/JDmKy2 JDeveloper & ADF? How to Search in Views - Part 4 || Oracle ADF http://dlvr.it/1dpDjZ WebLogic Community Java Message Service with Java and Spring Framework on Oracle WebLogic; Webcast May 15th 2012 http://wp.me/p1LMIb-gS Andreas Koop? new post ADF Bug or Feature? Non-Breaking Space outside required icon style http://bit.ly/KDZnUo Oracle WebLogic? Don't miss this month's WebLogic DevCast: WebLogic JMS and Spring JMS http://bit.ly/J6g2ST Tuesday May 15th 10:00am PT JDeveloper & ADF How To Disable SELECT COUNT Execution for ADF Table Rendering http://dlvr.it/1dqKH6 OracleSupport_WLS? #SSL and security has its own Information Center, http://bit.ly/LP8Vil for troubleshooting, install, config and more NetBeans Team? Featured #NetBeans plugin is @Codename_One for creating native apps for major mobile platforms: http://plugins.netbeans.org/ JDeveloper & ADF? Using JDeveloper HTTP Analyser to intercept/forward requests http://dlvr.it/1Yzl4J Nicolas Lorain? Create native looks for JavaFX applications: JavaFX-CSS-Themes · http://buff.ly/M0jel0 by Gregg Setzer Devoxx? Want to make the world a better place? Then get involved in Random Hacks of Kindness on June 2 - 3 in Belgium @ http://www.rhok.be #RHoK WebLogic Community top tweets WebLogic Partner Community – May 2012 Click here #WebLogicCommunity Michel Schildmeijer Oracle Traffic Director 11g http://lnkd.in/-mm3Vy Andrejus Baranovskis? Proactively Monitoring JDeveloper 11g IDE Heap Memory http://fb.me/16YZErPrx Arun Gupta? 80+ attendees building a #javaee6 application using NetBeans/WebLogic at Java Day, Istanbul fun times! http://pic.twitter.com/odY19daW A. Chatziantoniou? Just registered for the Oracle FMW Summer Camp in Lisbon. Looking forward to learn, meet friends and try to buy ice cream on the beach OTNArchBeat Another Myth Debunked: 200 Continuous Redeployments with WebLogic|@munz http://bit.ly/JiPyM7 Oracle WebLogic? Need to learn more on #WebLogic Server #JVM performance tuning? http://bit.ly/MN UxHx GlassFish? Dukes Choice Awards 2012 Nominations Are Open: 2012 Duke's Choice Award are open for nominations. These awards http://bit.ly/Ksk4U3 Justin Kestelyn? Major cloud-related announcements from Larry Ellison and Mark Hurd on June 6 http://bit.ly/KTJiII Nicolas Lorain Transparent Windows (Stage) with #JavaFX 2 : Adam Bien's Weblog http://j.mp/INgq8K WebLogic Community Web Services with JAX and Spring on WebLogic–Webcast May 30th 2012 #WebLogicCommunity #weblogic #opn JDeveloper & ADF Oracle ADF - How to work with Dates http://dlvr.it/1Y70zw OracleBlogs Web Services with JAX and Spring on WebLogicWebcast May 30th 2012 http://ow.ly/1k2WtO Adam Bien? Summer Java EE Workshops: 23.05, Amsterdam Airport Java EE Hacking, Without Airport. The dutch version of Airport http://bit.ly/JeP6hV JDeveloper & ADF ADF 11g: BC4J or EJB3. http://bit.ly/JVVFZF ADF EMG? Great discussion with JSF guru Andy Schwartz on the forum - 38 posts! Check it out: here Devoxx? Oracle (http://www.oracle.com ) joins Devoxx 2012 as the first Premium partner, welcome aboard! Nicolas Lorain Developing a Simple Todo Application using #JavaFX, #Java and #MongoDB- Part-1JavaBeat http://j.mp/IDGxLA Nicolas Lorain Preview of JavaFX 2.2 canvas feature > Harmonic Code: Death bitmaps could be beautiful... Part I http://buff.ly/KyAXg5 #JavaFX OTNArchBeat?? New York Coherence Special Interest Group (NYCSIG) - May 24 - NYC http://bit.ly/JzJcbT WebLogic Community iAS upgrade to WebLogic watch #C2B2 online seminar http://youtu.be/5m2CNUjBIGQ #WebLogicCommunity Ruth Collett? Join Oracle in #Joburg on May 21 for OTN Developer Day - sessions on #Java #JavaEE 6/7 and much more! http://bit.ly/IENwnD WebLogic Community? Sending out invitations to our advanced Fusion Middleware Summer Camps! Want to learn more register for the community Ruth Collett? Join @ArunGupta in Istanbul this Monday to hear the latest on #JavaEE 6/7 http://bit.ly/Je63cc GlassFish? NetBeans 7.2 Beta - Built for Speed, Deploy Apps to Oracle Cloud: NetBeans 7.2 Beta is now available. The http://bit.ly/LxMMTK Lucas Jellema My latest SlideShare upload : Java ain't scary - introducing Java to PL/SQ. here via @slideshare JDeveloper & ADF? #Developer #free#ADF training in #Scotland - June 13. More information: http://bit.ly/LbPLlf AMIS, Oracle & Java? AMIS behaalt als eerste in Nedeland de Oracle ADF specialisatie - Channelworld nieuwsChannelconnect: http://bit.ly/JzAcB4 WebLogic Community Web Services with JAX and Spring on WebLogic&ndash;Webcast May 30th 2012 http://wp.me/p1LMIb-gX Nicolas Lorain?@ JavaFX-based SimpleDateFormat Demonstrator http://j.mp/KFCVOi #JavaFX via Dustin Marx Oracle Exalogic? Are you an Oracle partner? There's news on the Oracle Partner Network about #Exalogic specializations - http://bit.ly/Mt3ANY JDeveloper & ADF Shorter URL for your ADF application http://dlvr.it/1XqNLY OTNArchBeat? Bay Area Coherence Special Interest Group (BACSIG) Meeting June 7 http://bit.ly/JAa0Lx OTNArchBeat? Java EE 6 Sample Application on WebLogic 12c: Conference Planner | @arungupta http://bit.ly/LPvof4 JDeveloper & ADF? Excellent example of Oracle ADF - Google Maps/Earth integration http://dlvr.it/1cbc80 JDeveloper & ADF Setting Up JDeveloper's Embedded WLS for MySQL http://dlvr.it/1c4b8P JDeveloper & ADF? Solution for Sharing Global User Data in ADF BC http://dlvr.it/1cc7SJ Java? Java Magazine May/June #javaee #javafx #javame #openJDK #hotspot #wicket #lotsmore http://ow.ly/aX07v Oracle WebLogic? http://bit.ly/JxQsnS if you have trouble finding the right #patchset when doing an upgrade to your #weblogic server OracleEnterpriseMgr 15 minutes to go before we start our Application Testing Suite 12.1 webcast. http://bit.ly/JHyTEe Learn from the lead PM what's new. #em12c Sten Vesterli Eating your own dog food - Oracle support site finally in ADF: http://lnkd.in/s6hg_p Adam Bien Project: "Jenever" (=poison) checked-in with GIT:here CU at http://workshops.adam-bien.com. Thanks for attending! OTNArchBeat Web Service Development with NetBeans and Testing with WebLogic Admin Console | @munz http://bit.ly/JcWk34 Please feel free to send us your news! And add your blog to our SOA blog wiki

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  • Beware Sneaky Reads with Unique Indexes

    - by Paul White NZ
    A few days ago, Sandra Mueller (twitter | blog) asked a question using twitter’s #sqlhelp hash tag: “Might SQL Server retrieve (out-of-row) LOB data from a table, even if the column isn’t referenced in the query?” Leaving aside trivial cases (like selecting a computed column that does reference the LOB data), one might be tempted to say that no, SQL Server does not read data you haven’t asked for.  In general, that’s quite correct; however there are cases where SQL Server might sneakily retrieve a LOB column… Example Table Here’s a T-SQL script to create that table and populate it with 1,000 rows: CREATE TABLE dbo.LOBtest ( pk INTEGER IDENTITY NOT NULL, some_value INTEGER NULL, lob_data VARCHAR(MAX) NULL, another_column CHAR(5) NULL, CONSTRAINT [PK dbo.LOBtest pk] PRIMARY KEY CLUSTERED (pk ASC) ); GO DECLARE @Data VARCHAR(MAX); SET @Data = REPLICATE(CONVERT(VARCHAR(MAX), 'x'), 65540);   WITH Numbers (n) AS ( SELECT ROW_NUMBER() OVER (ORDER BY (SELECT 0)) FROM master.sys.columns C1, master.sys.columns C2 ) INSERT LOBtest WITH (TABLOCKX) ( some_value, lob_data ) SELECT TOP (1000) N.n, @Data FROM Numbers N WHERE N.n <= 1000; Test 1: A Simple Update Let’s run a query to subtract one from every value in the some_value column: UPDATE dbo.LOBtest WITH (TABLOCKX) SET some_value = some_value - 1; As you might expect, modifying this integer column in 1,000 rows doesn’t take very long, or use many resources.  The STATITICS IO and TIME output shows a total of 9 logical reads, and 25ms elapsed time.  The query plan is also very simple: Looking at the Clustered Index Scan, we can see that SQL Server only retrieves the pk and some_value columns during the scan: The pk column is needed by the Clustered Index Update operator to uniquely identify the row that is being changed.  The some_value column is used by the Compute Scalar to calculate the new value.  (In case you are wondering what the Top operator is for, it is used to enforce SET ROWCOUNT). Test 2: Simple Update with an Index Now let’s create a nonclustered index keyed on the some_value column, with lob_data as an included column: CREATE NONCLUSTERED INDEX [IX dbo.LOBtest some_value (lob_data)] ON dbo.LOBtest (some_value) INCLUDE ( lob_data ) WITH ( FILLFACTOR = 100, MAXDOP = 1, SORT_IN_TEMPDB = ON ); This is not a useful index for our simple update query; imagine that someone else created it for a different purpose.  Let’s run our update query again: UPDATE dbo.LOBtest WITH (TABLOCKX) SET some_value = some_value - 1; We find that it now requires 4,014 logical reads and the elapsed query time has increased to around 100ms.  The extra logical reads (4 per row) are an expected consequence of maintaining the nonclustered index. The query plan is very similar to before (click to enlarge): The Clustered Index Update operator picks up the extra work of maintaining the nonclustered index. The new Compute Scalar operators detect whether the value in the some_value column has actually been changed by the update.  SQL Server may be able to skip maintaining the nonclustered index if the value hasn’t changed (see my previous post on non-updating updates for details).  Our simple query does change the value of some_data in every row, so this optimization doesn’t add any value in this specific case. The output list of columns from the Clustered Index Scan hasn’t changed from the one shown previously: SQL Server still just reads the pk and some_data columns.  Cool. Overall then, adding the nonclustered index hasn’t had any startling effects, and the LOB column data still isn’t being read from the table.  Let’s see what happens if we make the nonclustered index unique. Test 3: Simple Update with a Unique Index Here’s the script to create a new unique index, and drop the old one: CREATE UNIQUE NONCLUSTERED INDEX [UQ dbo.LOBtest some_value (lob_data)] ON dbo.LOBtest (some_value) INCLUDE ( lob_data ) WITH ( FILLFACTOR = 100, MAXDOP = 1, SORT_IN_TEMPDB = ON ); GO DROP INDEX [IX dbo.LOBtest some_value (lob_data)] ON dbo.LOBtest; Remember that SQL Server only enforces uniqueness on index keys (the some_data column).  The lob_data column is simply stored at the leaf-level of the non-clustered index.  With that in mind, we might expect this change to make very little difference.  Let’s see: UPDATE dbo.LOBtest WITH (TABLOCKX) SET some_value = some_value - 1; Whoa!  Now look at the elapsed time and logical reads: Scan count 1, logical reads 2016, physical reads 0, read-ahead reads 0, lob logical reads 36015, lob physical reads 0, lob read-ahead reads 15992.   CPU time = 172 ms, elapsed time = 16172 ms. Even with all the data and index pages in memory, the query took over 16 seconds to update just 1,000 rows, performing over 52,000 LOB logical reads (nearly 16,000 of those using read-ahead). Why on earth is SQL Server reading LOB data in a query that only updates a single integer column? The Query Plan The query plan for test 3 looks a bit more complex than before: In fact, the bottom level is exactly the same as we saw with the non-unique index.  The top level has heaps of new stuff though, which I’ll come to in a moment. You might be expecting to find that the Clustered Index Scan is now reading the lob_data column (for some reason).  After all, we need to explain where all the LOB logical reads are coming from.  Sadly, when we look at the properties of the Clustered Index Scan, we see exactly the same as before: SQL Server is still only reading the pk and some_value columns – so what’s doing the LOB reads? Updates that Sneakily Read Data We have to go as far as the Clustered Index Update operator before we see LOB data in the output list: [Expr1020] is a bit flag added by an earlier Compute Scalar.  It is set true if the some_value column has not been changed (part of the non-updating updates optimization I mentioned earlier). The Clustered Index Update operator adds two new columns: the lob_data column, and some_value_OLD.  The some_value_OLD column, as the name suggests, is the pre-update value of the some_value column.  At this point, the clustered index has already been updated with the new value, but we haven’t touched the nonclustered index yet. An interesting observation here is that the Clustered Index Update operator can read a column into the data flow as part of its update operation.  SQL Server could have read the LOB data as part of the initial Clustered Index Scan, but that would mean carrying the data through all the operations that occur prior to the Clustered Index Update.  The server knows it will have to go back to the clustered index row to update it, so it delays reading the LOB data until then.  Sneaky! Why the LOB Data Is Needed This is all very interesting (I hope), but why is SQL Server reading the LOB data?  For that matter, why does it need to pass the pre-update value of the some_value column out of the Clustered Index Update? The answer relates to the top row of the query plan for test 3.  I’ll reproduce it here for convenience: Notice that this is a wide (per-index) update plan.  SQL Server used a narrow (per-row) update plan in test 2, where the Clustered Index Update took care of maintaining the nonclustered index too.  I’ll talk more about this difference shortly. The Split/Sort/Collapse combination is an optimization, which aims to make per-index update plans more efficient.  It does this by breaking each update into a delete/insert pair, reordering the operations, removing any redundant operations, and finally applying the net effect of all the changes to the nonclustered index. Imagine we had a unique index which currently holds three rows with the values 1, 2, and 3.  If we run a query that adds 1 to each row value, we would end up with values 2, 3, and 4.  The net effect of all the changes is the same as if we simply deleted the value 1, and added a new value 4. By applying net changes, SQL Server can also avoid false unique-key violations.  If we tried to immediately update the value 1 to a 2, it would conflict with the existing value 2 (which would soon be updated to 3 of course) and the query would fail.  You might argue that SQL Server could avoid the uniqueness violation by starting with the highest value (3) and working down.  That’s fine, but it’s not possible to generalize this logic to work with every possible update query. SQL Server has to use a wide update plan if it sees any risk of false uniqueness violations.  It’s worth noting that the logic SQL Server uses to detect whether these violations are possible has definite limits.  As a result, you will often receive a wide update plan, even when you can see that no violations are possible. Another benefit of this optimization is that it includes a sort on the index key as part of its work.  Processing the index changes in index key order promotes sequential I/O against the nonclustered index. A side-effect of all this is that the net changes might include one or more inserts.  In order to insert a new row in the index, SQL Server obviously needs all the columns – the key column and the included LOB column.  This is the reason SQL Server reads the LOB data as part of the Clustered Index Update. In addition, the some_value_OLD column is required by the Split operator (it turns updates into delete/insert pairs).  In order to generate the correct index key delete operation, it needs the old key value. The irony is that in this case the Split/Sort/Collapse optimization is anything but.  Reading all that LOB data is extremely expensive, so it is sad that the current version of SQL Server has no way to avoid it. Finally, for completeness, I should mention that the Filter operator is there to filter out the non-updating updates. Beating the Set-Based Update with a Cursor One situation where SQL Server can see that false unique-key violations aren’t possible is where it can guarantee that only one row is being updated.  Armed with this knowledge, we can write a cursor (or the WHILE-loop equivalent) that updates one row at a time, and so avoids reading the LOB data: SET NOCOUNT ON; SET STATISTICS XML, IO, TIME OFF;   DECLARE @PK INTEGER, @StartTime DATETIME; SET @StartTime = GETUTCDATE();   DECLARE curUpdate CURSOR LOCAL FORWARD_ONLY KEYSET SCROLL_LOCKS FOR SELECT L.pk FROM LOBtest L ORDER BY L.pk ASC;   OPEN curUpdate;   WHILE (1 = 1) BEGIN FETCH NEXT FROM curUpdate INTO @PK;   IF @@FETCH_STATUS = -1 BREAK; IF @@FETCH_STATUS = -2 CONTINUE;   UPDATE dbo.LOBtest SET some_value = some_value - 1 WHERE CURRENT OF curUpdate; END;   CLOSE curUpdate; DEALLOCATE curUpdate;   SELECT DATEDIFF(MILLISECOND, @StartTime, GETUTCDATE()); That completes the update in 1280 milliseconds (remember test 3 took over 16 seconds!) I used the WHERE CURRENT OF syntax there and a KEYSET cursor, just for the fun of it.  One could just as well use a WHERE clause that specified the primary key value instead. Clustered Indexes A clustered index is the ultimate index with included columns: all non-key columns are included columns in a clustered index.  Let’s re-create the test table and data with an updatable primary key, and without any non-clustered indexes: IF OBJECT_ID(N'dbo.LOBtest', N'U') IS NOT NULL DROP TABLE dbo.LOBtest; GO CREATE TABLE dbo.LOBtest ( pk INTEGER NOT NULL, some_value INTEGER NULL, lob_data VARCHAR(MAX) NULL, another_column CHAR(5) NULL, CONSTRAINT [PK dbo.LOBtest pk] PRIMARY KEY CLUSTERED (pk ASC) ); GO DECLARE @Data VARCHAR(MAX); SET @Data = REPLICATE(CONVERT(VARCHAR(MAX), 'x'), 65540);   WITH Numbers (n) AS ( SELECT ROW_NUMBER() OVER (ORDER BY (SELECT 0)) FROM master.sys.columns C1, master.sys.columns C2 ) INSERT LOBtest WITH (TABLOCKX) ( pk, some_value, lob_data ) SELECT TOP (1000) N.n, N.n, @Data FROM Numbers N WHERE N.n <= 1000; Now here’s a query to modify the cluster keys: UPDATE dbo.LOBtest SET pk = pk + 1; The query plan is: As you can see, the Split/Sort/Collapse optimization is present, and we also gain an Eager Table Spool, for Halloween protection.  In addition, SQL Server now has no choice but to read the LOB data in the Clustered Index Scan: The performance is not great, as you might expect (even though there is no non-clustered index to maintain): Table 'LOBtest'. Scan count 1, logical reads 2011, physical reads 0, read-ahead reads 0, lob logical reads 36015, lob physical reads 0, lob read-ahead reads 15992.   Table 'Worktable'. Scan count 1, logical reads 2040, physical reads 0, read-ahead reads 0, lob logical reads 34000, lob physical reads 0, lob read-ahead reads 8000.   SQL Server Execution Times: CPU time = 483 ms, elapsed time = 17884 ms. Notice how the LOB data is read twice: once from the Clustered Index Scan, and again from the work table in tempdb used by the Eager Spool. If you try the same test with a non-unique clustered index (rather than a primary key), you’ll get a much more efficient plan that just passes the cluster key (including uniqueifier) around (no LOB data or other non-key columns): A unique non-clustered index (on a heap) works well too: Both those queries complete in a few tens of milliseconds, with no LOB reads, and just a few thousand logical reads.  (In fact the heap is rather more efficient). There are lots more fun combinations to try that I don’t have space for here. Final Thoughts The behaviour shown in this post is not limited to LOB data by any means.  If the conditions are met, any unique index that has included columns can produce similar behaviour – something to bear in mind when adding large INCLUDE columns to achieve covering queries, perhaps. Paul White Email: [email protected] Twitter: @PaulWhiteNZ

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  • 10.10 freezing when sftp downloading

    - by aGr
    My ubuntu 10.10 is freezing during downloading from my other computer on sftp. I thought it might be some nautilus issues so I tried it via command line and I got the same thing - after few minutes the whole computer freezes. Mostly the numlock led is blinking (I've heard somewhere that this means a kernel panic), but not in 100% cases. I dunno if that helps but here is a log from /var/log/message in the time that this happened. At least I hope so - it wasn't that big, when it happened before. But this looks quite "errorish", right? (isn't complete - see bottom) Jan 5 17:57:49 tomas-ntb kernel: imklog 4.2.0, log source = /proc/kmsg started. Jan 5 17:57:49 tomas-ntb rsyslogd: [origin software="rsyslogd" swVersion="4.2.0" x-pid="953" x-info="http://www.rsyslog.com"] (re)start Jan 5 17:57:49 tomas-ntb rsyslogd: rsyslogd's groupid changed to 103 Jan 5 17:57:49 tomas-ntb rsyslogd: rsyslogd's userid changed to 101 Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] Initializing cgroup subsys cpuset Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] Initializing cgroup subsys cpu Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] Linux version 2.6.35-24-generic (buildd@vernadsky) (gcc version 4.4.5 (Ubuntu/Linaro 4.4.4-14ubuntu5) ) #42-Ubuntu SMP Thu Dec 2 01:41:57 UTC 2010 (Ubuntu 2.6.35-24.42-generic 2.6.35.8) Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] BIOS-provided physical RAM map: Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] BIOS-e820: 0000000000000000 - 000000000009e800 (usable) Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] BIOS-e820: 000000000009e800 - 00000000000a0000 (reserved) Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved) Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] BIOS-e820: 0000000000100000 - 00000000dffa8000 (usable) Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] BIOS-e820: 00000000dffa8000 - 00000000dffb0000 (ACPI NVS) Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] BIOS-e820: 00000000dffb0000 - 00000000dffbff00 (ACPI data) Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] BIOS-e820: 00000000dffbff00 - 00000000dfff0000 (ACPI NVS) Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] BIOS-e820: 00000000dfff0000 - 00000000e0000000 (reserved) Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] BIOS-e820: 00000000fec00000 - 00000000fec01000 (reserved) Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved) Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] BIOS-e820: 00000000ff700000 - 0000000100000000 (reserved) Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] BIOS-e820: 0000000100000000 - 0000000120000000 (usable) Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] BIOS-e820: 0000000120000000 - 0000000140000000 (reserved) Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] Notice: NX (Execute Disable) protection cannot be enabled: non-PAE kernel! Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] DMI 2.5 present. Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] AMI BIOS detected: BIOS may corrupt low RAM, working around it. Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] last_pfn = 0xdffa8 max_arch_pfn = 0x100000 Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] x86 PAT enabled: cpu 0, old 0x7040600070406, new 0x7010600070106 Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] Scanning 0 areas for low memory corruption Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] modified physical RAM map: Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] modified: 0000000000000000 - 0000000000010000 (reserved) Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] modified: 0000000000010000 - 000000000009e800 (usable) Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] modified: 000000000009e800 - 00000000000a0000 (reserved) Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] modified: 00000000000e0000 - 0000000000100000 (reserved) Jan 5 17:57:49 tomas-ntb kernel: [ 0.000000] modified: 0000000000100000 - 00000000dffa8000 (usable) ... to long - for whole and better view click here

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  • Understanding C# async / await (1) Compilation

    - by Dixin
    Now the async / await keywords are in C#. Just like the async and ! in F#, this new C# feature provides great convenience. There are many nice documents talking about how to use async / await in specific scenarios, like using async methods in ASP.NET 4.5 and in ASP.NET MVC 4, etc. In this article we will look at the real code working behind the syntax sugar. According to MSDN: The async modifier indicates that the method, lambda expression, or anonymous method that it modifies is asynchronous. Since lambda expression / anonymous method will be compiled to normal method, we will focus on normal async method. Preparation First of all, Some helper methods need to make up. internal class HelperMethods { internal static int Method(int arg0, int arg1) { // Do some IO. WebClient client = new WebClient(); Enumerable.Repeat("http://weblogs.asp.net/dixin", 10) .Select(client.DownloadString).ToArray(); int result = arg0 + arg1; return result; } internal static Task<int> MethodTask(int arg0, int arg1) { Task<int> task = new Task<int>(() => Method(arg0, arg1)); task.Start(); // Hot task (started task) should always be returned. return task; } internal static void Before() { } internal static void Continuation1(int arg) { } internal static void Continuation2(int arg) { } } Here Method() is a long running method doing some IO. Then MethodTask() wraps it into a Task and return that Task. Nothing special here. Await something in async method Since MethodTask() returns Task, let’s try to await it: internal class AsyncMethods { internal static async Task<int> MethodAsync(int arg0, int arg1) { int result = await HelperMethods.MethodTask(arg0, arg1); return result; } } Because we used await in the method, async must be put on the method. Now we get the first async method. According to the naming convenience, it is called MethodAsync. Of course a async method can be awaited. So we have a CallMethodAsync() to call MethodAsync(): internal class AsyncMethods { internal static async Task<int> CallMethodAsync(int arg0, int arg1) { int result = await MethodAsync(arg0, arg1); return result; } } After compilation, MethodAsync() and CallMethodAsync() becomes the same logic. This is the code of MethodAsyc(): internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(MethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MethodAsync(int arg0, int arg1) { MethodAsyncStateMachine methodAsyncStateMachine = new MethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; methodAsyncStateMachine.Builder.Start(ref methodAsyncStateMachine); return methodAsyncStateMachine.Builder.Task; } } It just creates and starts a state machine MethodAsyncStateMachine: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MethodAsyncStateMachine : IAsyncStateMachine { public int State; public AsyncTaskMethodBuilder<int> Builder; public int Arg0; public int Arg1; public int Result; private TaskAwaiter<int> awaitor; void IAsyncStateMachine.MoveNext() { try { if (this.State != 0) { this.awaitor = HelperMethods.MethodTask(this.Arg0, this.Arg1).GetAwaiter(); if (!this.awaitor.IsCompleted) { this.State = 0; this.Builder.AwaitUnsafeOnCompleted(ref this.awaitor, ref this); return; } } else { this.State = -1; } this.Result = this.awaitor.GetResult(); } catch (Exception exception) { this.State = -2; this.Builder.SetException(exception); return; } this.State = -2; this.Builder.SetResult(this.Result); } [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine param0) { this.Builder.SetStateMachine(param0); } } The generated code has been cleaned up so it is readable and can be compiled. Several things can be observed here: The async modifier is gone, which shows, unlike other modifiers (e.g. static), there is no such IL/CLR level “async” stuff. It becomes a AsyncStateMachineAttribute. This is similar to the compilation of extension method. The generated state machine is very similar to the state machine of C# yield syntax sugar. The local variables (arg0, arg1, result) are compiled to fields of the state machine. The real code (await HelperMethods.MethodTask(arg0, arg1)) is compiled into MoveNext(): HelperMethods.MethodTask(this.Arg0, this.Arg1).GetAwaiter(). CallMethodAsync() will create and start its own state machine CallMethodAsyncStateMachine: internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(CallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> CallMethodAsync(int arg0, int arg1) { CallMethodAsyncStateMachine callMethodAsyncStateMachine = new CallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; callMethodAsyncStateMachine.Builder.Start(ref callMethodAsyncStateMachine); return callMethodAsyncStateMachine.Builder.Task; } } CallMethodAsyncStateMachine has the same logic as MethodAsyncStateMachine above. The detail of the state machine will be discussed soon. Now it is clear that: async /await is a C# level syntax sugar. There is no difference to await a async method or a normal method. A method returning Task will be awaitable. State machine and continuation To demonstrate more details in the state machine, a more complex method is created: internal class AsyncMethods { internal static async Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { HelperMethods.Before(); int resultOfAwait1 = await MethodAsync(arg0, arg1); HelperMethods.Continuation1(resultOfAwait1); int resultOfAwait2 = await MethodAsync(arg2, arg3); HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; return resultToReturn; } } In this method: There are multiple awaits. There are code before the awaits, and continuation code after each await After compilation, this multi-await method becomes the same as above single-await methods: internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(MultiCallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { MultiCallMethodAsyncStateMachine multiCallMethodAsyncStateMachine = new MultiCallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Arg2 = arg2, Arg3 = arg3, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; multiCallMethodAsyncStateMachine.Builder.Start(ref multiCallMethodAsyncStateMachine); return multiCallMethodAsyncStateMachine.Builder.Task; } } It creates and starts one single state machine, MultiCallMethodAsyncStateMachine: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MultiCallMethodAsyncStateMachine : IAsyncStateMachine { public int State; public AsyncTaskMethodBuilder<int> Builder; public int Arg0; public int Arg1; public int Arg2; public int Arg3; public int ResultOfAwait1; public int ResultOfAwait2; public int ResultToReturn; private TaskAwaiter<int> awaiter; void IAsyncStateMachine.MoveNext() { try { switch (this.State) { case -1: HelperMethods.Before(); this.awaiter = AsyncMethods.MethodAsync(this.Arg0, this.Arg1).GetAwaiter(); if (!this.awaiter.IsCompleted) { this.State = 0; this.Builder.AwaitUnsafeOnCompleted(ref this.awaiter, ref this); } break; case 0: this.ResultOfAwait1 = this.awaiter.GetResult(); HelperMethods.Continuation1(this.ResultOfAwait1); this.awaiter = AsyncMethods.MethodAsync(this.Arg2, this.Arg3).GetAwaiter(); if (!this.awaiter.IsCompleted) { this.State = 1; this.Builder.AwaitUnsafeOnCompleted(ref this.awaiter, ref this); } break; case 1: this.ResultOfAwait2 = this.awaiter.GetResult(); HelperMethods.Continuation2(this.ResultOfAwait2); this.ResultToReturn = this.ResultOfAwait1 + this.ResultOfAwait2; this.State = -2; this.Builder.SetResult(this.ResultToReturn); break; } } catch (Exception exception) { this.State = -2; this.Builder.SetException(exception); } } [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine stateMachine) { this.Builder.SetStateMachine(stateMachine); } } The above code is already cleaned up, but there are still a lot of things. More clean up can be done, and the state machine can be very simple: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MultiCallMethodAsyncStateMachine : IAsyncStateMachine { // State: // -1: Begin // 0: 1st await is done // 1: 2nd await is done // ... // -2: End public int State; public TaskCompletionSource<int> ResultToReturn; // int resultToReturn ... public int Arg0; // int Arg0 public int Arg1; // int arg1 public int Arg2; // int arg2 public int Arg3; // int arg3 public int ResultOfAwait1; // int resultOfAwait1 ... public int ResultOfAwait2; // int resultOfAwait2 ... private Task<int> currentTaskToAwait; /// <summary> /// Moves the state machine to its next state. /// </summary> void IAsyncStateMachine.MoveNext() { try { switch (this.State) { // Orginal code is splitted by "case"s: // case -1: // HelperMethods.Before(); // MethodAsync(Arg0, arg1); // case 0: // int resultOfAwait1 = await ... // HelperMethods.Continuation1(resultOfAwait1); // MethodAsync(arg2, arg3); // case 1: // int resultOfAwait2 = await ... // HelperMethods.Continuation2(resultOfAwait2); // int resultToReturn = resultOfAwait1 + resultOfAwait2; // return resultToReturn; case -1: // -1 is begin. HelperMethods.Before(); // Code before 1st await. this.currentTaskToAwait = AsyncMethods.MethodAsync(this.Arg0, this.Arg1); // 1st task to await // When this.currentTaskToAwait is done, run this.MoveNext() and go to case 0. this.State = 0; IAsyncStateMachine this1 = this; // Cannot use "this" in lambda so create a local variable. this.currentTaskToAwait.ContinueWith(_ => this1.MoveNext()); // Callback break; case 0: // Now 1st await is done. this.ResultOfAwait1 = this.currentTaskToAwait.Result; // Get 1st await's result. HelperMethods.Continuation1(this.ResultOfAwait1); // Code after 1st await and before 2nd await. this.currentTaskToAwait = AsyncMethods.MethodAsync(this.Arg2, this.Arg3); // 2nd task to await // When this.currentTaskToAwait is done, run this.MoveNext() and go to case 1. this.State = 1; IAsyncStateMachine this2 = this; // Cannot use "this" in lambda so create a local variable. this.currentTaskToAwait.ContinueWith(_ => this2.MoveNext()); // Callback break; case 1: // Now 2nd await is done. this.ResultOfAwait2 = this.currentTaskToAwait.Result; // Get 2nd await's result. HelperMethods.Continuation2(this.ResultOfAwait2); // Code after 2nd await. int resultToReturn = this.ResultOfAwait1 + this.ResultOfAwait2; // Code after 2nd await. // End with resultToReturn. this.State = -2; // -2 is end. this.ResultToReturn.SetResult(resultToReturn); break; } } catch (Exception exception) { // End with exception. this.State = -2; // -2 is end. this.ResultToReturn.SetException(exception); } } /// <summary> /// Configures the state machine with a heap-allocated replica. /// </summary> /// <param name="stateMachine">The heap-allocated replica.</param> [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine stateMachine) { // No core logic. } } Only Task and TaskCompletionSource are involved in this version. And MultiCallMethodAsync() can be simplified to: [DebuggerStepThrough] [AsyncStateMachine(typeof(MultiCallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MultiCallMethodAsync_(int arg0, int arg1, int arg2, int arg3) { MultiCallMethodAsyncStateMachine multiCallMethodAsyncStateMachine = new MultiCallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Arg2 = arg2, Arg3 = arg3, ResultToReturn = new TaskCompletionSource<int>(), // -1: Begin // 0: 1st await is done // 1: 2nd await is done // ... // -2: End State = -1 }; (multiCallMethodAsyncStateMachine as IAsyncStateMachine).MoveNext(); // Original code are in this method. return multiCallMethodAsyncStateMachine.ResultToReturn.Task; } Now the whole state machine becomes very clear - it is about callback: Original code are split into pieces by “await”s, and each piece is put into each “case” in the state machine. Here the 2 awaits split the code into 3 pieces, so there are 3 “case”s. The “piece”s are chained by callback, that is done by Builder.AwaitUnsafeOnCompleted(callback), or currentTaskToAwait.ContinueWith(callback) in the simplified code. A previous “piece” will end with a Task (which is to be awaited), when the task is done, it will callback the next “piece”. The state machine’s state works with the “case”s to ensure the code “piece”s executes one after another. Callback Since it is about callback, the simplification  can go even further – the entire state machine can be completely purged. Now MultiCallMethodAsync() becomes: internal static Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { TaskCompletionSource<int> taskCompletionSource = new TaskCompletionSource<int>(); try { // Oringinal code begins. HelperMethods.Before(); MethodAsync(arg0, arg1).ContinueWith(await1 => { int resultOfAwait1 = await1.Result; HelperMethods.Continuation1(resultOfAwait1); MethodAsync(arg2, arg3).ContinueWith(await2 => { int resultOfAwait2 = await2.Result; HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; // Oringinal code ends. taskCompletionSource.SetResult(resultToReturn); }); }); } catch (Exception exception) { taskCompletionSource.SetException(exception); } return taskCompletionSource.Task; } Please compare with the original async / await code: HelperMethods.Before(); int resultOfAwait1 = await MethodAsync(arg0, arg1); HelperMethods.Continuation1(resultOfAwait1); int resultOfAwait2 = await MethodAsync(arg2, arg3); HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; return resultToReturn; Yeah that is the magic of C# async / await: Await is literally pretending to wait. In a await expression, a Task object will be return immediately so that caller is not blocked. The continuation code is compiled as that Task’s callback code. When that task is done, continuation code will execute. Please notice that many details inside the state machine are omitted for simplicity, like context caring, etc. If you want to have a detailed picture, please do check out the source code of AsyncTaskMethodBuilder and TaskAwaiter.

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  • Interviews: Going Beyond the Technical Quiz

    - by Tony Davis
    All developers will be familiar with the basic format of a technical interview. After a bout of CV-trawling to gauge basic experience, strengths and weaknesses, the interview turns technical. The whiteboard takes center stage and the challenge is set to design a function or query, or solve what on the face of it might seem a disarmingly simple programming puzzle. Most developers will have experienced those few panic-stricken moments, when one’s mind goes as blank as the whiteboard, before un-popping the marker pen, and hopefully one’s mental functions, to work through the problem. It is a way to probe the candidate’s knowledge of basic programming structures and techniques and to challenge their critical thinking. However, these challenges or puzzles, often devised by some of the smartest brains in the development team, have a tendency to become unnecessarily ‘tricksy’. They often seem somewhat academic in nature. While the candidate straight out of IT school might breeze through the construction of a Markov chain, a candidate with bags of practical experience but less in the way of formal training could become nonplussed. Also, a whiteboard and a marker pen make up only a very small part of the toolkit that a programmer will use in everyday work. I remember vividly my first job interview, for a position as technical editor. It went well, but after the usual CV grilling and technical questions, I was only halfway there. Later, they sat me alongside a team of editors, in front of a computer loaded with MS Word and copy of SQL Server Query Analyzer, and my task was to edit a real chapter for a real SQL Server book that they planned to publish, including validating and testing all the code. It was a tough challenge but I came away with a sound knowledge of the sort of work I’d do, and its context. It makes perfect sense, yet my impression is that many organizations don’t do this. Indeed, it is only relatively recently that Red Gate started to move over to this model for developer interviews. Now, instead of, or perhaps in addition to, the whiteboard challenges, the candidate can expect to sit with their prospective team, in front of Visual Studio, loaded with all the useful tools in the developer’s kit (ReSharper and so on) and asked to, for example, analyze and improve a real piece of software. The same principles should apply when interviewing for a database positon. In addition to the usual questions challenging the candidate’s knowledge of such things as b-trees, object permissions, database recovery models, and so on, sit the candidate down with the other database developers or DBAs. Arm them with a copy of Management Studio, and a few other tools, then challenge them to discover the flaws in a stored procedure, and improve its performance. Or present them with a corrupt database and ask them to get the database back online, and discover the cause of the corruption.

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  • Understanding C# async / await (1) Compilation

    - by Dixin
    Now the async / await keywords are in C#. Just like the async and ! in F#, this new C# feature provides great convenience. There are many nice documents talking about how to use async / await in specific scenarios, like using async methods in ASP.NET 4.5 and in ASP.NET MVC 4, etc. In this article we will look at the real code working behind the syntax sugar. According to MSDN: The async modifier indicates that the method, lambda expression, or anonymous method that it modifies is asynchronous. Since lambda expression / anonymous method will be compiled to normal method, we will focus on normal async method. Preparation First of all, Some helper methods need to make up. internal class HelperMethods { internal static int Method(int arg0, int arg1) { // Do some IO. WebClient client = new WebClient(); Enumerable.Repeat("http://weblogs.asp.net/dixin", 10) .Select(client.DownloadString).ToArray(); int result = arg0 + arg1; return result; } internal static Task<int> MethodTask(int arg0, int arg1) { Task<int> task = new Task<int>(() => Method(arg0, arg1)); task.Start(); // Hot task (started task) should always be returned. return task; } internal static void Before() { } internal static void Continuation1(int arg) { } internal static void Continuation2(int arg) { } } Here Method() is a long running method doing some IO. Then MethodTask() wraps it into a Task and return that Task. Nothing special here. Await something in async method Since MethodTask() returns Task, let’s try to await it: internal class AsyncMethods { internal static async Task<int> MethodAsync(int arg0, int arg1) { int result = await HelperMethods.MethodTask(arg0, arg1); return result; } } Because we used await in the method, async must be put on the method. Now we get the first async method. According to the naming convenience, it is named MethodAsync. Of course a async method can be awaited. So we have a CallMethodAsync() to call MethodAsync(): internal class AsyncMethods { internal static async Task<int> CallMethodAsync(int arg0, int arg1) { int result = await MethodAsync(arg0, arg1); return result; } } After compilation, MethodAsync() and CallMethodAsync() becomes the same logic. This is the code of MethodAsyc(): internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(MethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MethodAsync(int arg0, int arg1) { MethodAsyncStateMachine methodAsyncStateMachine = new MethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; methodAsyncStateMachine.Builder.Start(ref methodAsyncStateMachine); return methodAsyncStateMachine.Builder.Task; } } It just creates and starts a state machine, MethodAsyncStateMachine: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MethodAsyncStateMachine : IAsyncStateMachine { public int State; public AsyncTaskMethodBuilder<int> Builder; public int Arg0; public int Arg1; public int Result; private TaskAwaiter<int> awaitor; void IAsyncStateMachine.MoveNext() { try { if (this.State != 0) { this.awaitor = HelperMethods.MethodTask(this.Arg0, this.Arg1).GetAwaiter(); if (!this.awaitor.IsCompleted) { this.State = 0; this.Builder.AwaitUnsafeOnCompleted(ref this.awaitor, ref this); return; } } else { this.State = -1; } this.Result = this.awaitor.GetResult(); } catch (Exception exception) { this.State = -2; this.Builder.SetException(exception); return; } this.State = -2; this.Builder.SetResult(this.Result); } [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine param0) { this.Builder.SetStateMachine(param0); } } The generated code has been refactored, so it is readable and can be compiled. Several things can be observed here: The async modifier is gone, which shows, unlike other modifiers (e.g. static), there is no such IL/CLR level “async” stuff. It becomes a AsyncStateMachineAttribute. This is similar to the compilation of extension method. The generated state machine is very similar to the state machine of C# yield syntax sugar. The local variables (arg0, arg1, result) are compiled to fields of the state machine. The real code (await HelperMethods.MethodTask(arg0, arg1)) is compiled into MoveNext(): HelperMethods.MethodTask(this.Arg0, this.Arg1).GetAwaiter(). CallMethodAsync() will create and start its own state machine CallMethodAsyncStateMachine: internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(CallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> CallMethodAsync(int arg0, int arg1) { CallMethodAsyncStateMachine callMethodAsyncStateMachine = new CallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; callMethodAsyncStateMachine.Builder.Start(ref callMethodAsyncStateMachine); return callMethodAsyncStateMachine.Builder.Task; } } CallMethodAsyncStateMachine has the same logic as MethodAsyncStateMachine above. The detail of the state machine will be discussed soon. Now it is clear that: async /await is a C# language level syntax sugar. There is no difference to await a async method or a normal method. As long as a method returns Task, it is awaitable. State machine and continuation To demonstrate more details in the state machine, a more complex method is created: internal class AsyncMethods { internal static async Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { HelperMethods.Before(); int resultOfAwait1 = await MethodAsync(arg0, arg1); HelperMethods.Continuation1(resultOfAwait1); int resultOfAwait2 = await MethodAsync(arg2, arg3); HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; return resultToReturn; } } In this method: There are multiple awaits. There are code before the awaits, and continuation code after each await After compilation, this multi-await method becomes the same as above single-await methods: internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(MultiCallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { MultiCallMethodAsyncStateMachine multiCallMethodAsyncStateMachine = new MultiCallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Arg2 = arg2, Arg3 = arg3, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; multiCallMethodAsyncStateMachine.Builder.Start(ref multiCallMethodAsyncStateMachine); return multiCallMethodAsyncStateMachine.Builder.Task; } } It creates and starts one single state machine, MultiCallMethodAsyncStateMachine: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MultiCallMethodAsyncStateMachine : IAsyncStateMachine { public int State; public AsyncTaskMethodBuilder<int> Builder; public int Arg0; public int Arg1; public int Arg2; public int Arg3; public int ResultOfAwait1; public int ResultOfAwait2; public int ResultToReturn; private TaskAwaiter<int> awaiter; void IAsyncStateMachine.MoveNext() { try { switch (this.State) { case -1: HelperMethods.Before(); this.awaiter = AsyncMethods.MethodAsync(this.Arg0, this.Arg1).GetAwaiter(); if (!this.awaiter.IsCompleted) { this.State = 0; this.Builder.AwaitUnsafeOnCompleted(ref this.awaiter, ref this); } break; case 0: this.ResultOfAwait1 = this.awaiter.GetResult(); HelperMethods.Continuation1(this.ResultOfAwait1); this.awaiter = AsyncMethods.MethodAsync(this.Arg2, this.Arg3).GetAwaiter(); if (!this.awaiter.IsCompleted) { this.State = 1; this.Builder.AwaitUnsafeOnCompleted(ref this.awaiter, ref this); } break; case 1: this.ResultOfAwait2 = this.awaiter.GetResult(); HelperMethods.Continuation2(this.ResultOfAwait2); this.ResultToReturn = this.ResultOfAwait1 + this.ResultOfAwait2; this.State = -2; this.Builder.SetResult(this.ResultToReturn); break; } } catch (Exception exception) { this.State = -2; this.Builder.SetException(exception); } } [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine stateMachine) { this.Builder.SetStateMachine(stateMachine); } } Once again, the above state machine code is already refactored, but it still has a lot of things. More clean up can be done if we only keep the core logic, and the state machine can become very simple: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MultiCallMethodAsyncStateMachine : IAsyncStateMachine { // State: // -1: Begin // 0: 1st await is done // 1: 2nd await is done // ... // -2: End public int State; public TaskCompletionSource<int> ResultToReturn; // int resultToReturn ... public int Arg0; // int Arg0 public int Arg1; // int arg1 public int Arg2; // int arg2 public int Arg3; // int arg3 public int ResultOfAwait1; // int resultOfAwait1 ... public int ResultOfAwait2; // int resultOfAwait2 ... private Task<int> currentTaskToAwait; /// <summary> /// Moves the state machine to its next state. /// </summary> public void MoveNext() // IAsyncStateMachine member. { try { switch (this.State) { // Original code is split by "await"s into "case"s: // case -1: // HelperMethods.Before(); // MethodAsync(Arg0, arg1); // case 0: // int resultOfAwait1 = await ... // HelperMethods.Continuation1(resultOfAwait1); // MethodAsync(arg2, arg3); // case 1: // int resultOfAwait2 = await ... // HelperMethods.Continuation2(resultOfAwait2); // int resultToReturn = resultOfAwait1 + resultOfAwait2; // return resultToReturn; case -1: // -1 is begin. HelperMethods.Before(); // Code before 1st await. this.currentTaskToAwait = AsyncMethods.MethodAsync(this.Arg0, this.Arg1); // 1st task to await // When this.currentTaskToAwait is done, run this.MoveNext() and go to case 0. this.State = 0; MultiCallMethodAsyncStateMachine that1 = this; // Cannot use "this" in lambda so create a local variable. this.currentTaskToAwait.ContinueWith(_ => that1.MoveNext()); break; case 0: // Now 1st await is done. this.ResultOfAwait1 = this.currentTaskToAwait.Result; // Get 1st await's result. HelperMethods.Continuation1(this.ResultOfAwait1); // Code after 1st await and before 2nd await. this.currentTaskToAwait = AsyncMethods.MethodAsync(this.Arg2, this.Arg3); // 2nd task to await // When this.currentTaskToAwait is done, run this.MoveNext() and go to case 1. this.State = 1; MultiCallMethodAsyncStateMachine that2 = this; this.currentTaskToAwait.ContinueWith(_ => that2.MoveNext()); break; case 1: // Now 2nd await is done. this.ResultOfAwait2 = this.currentTaskToAwait.Result; // Get 2nd await's result. HelperMethods.Continuation2(this.ResultOfAwait2); // Code after 2nd await. int resultToReturn = this.ResultOfAwait1 + this.ResultOfAwait2; // Code after 2nd await. // End with resultToReturn. this.State = -2; // -2 is end. this.ResultToReturn.SetResult(resultToReturn); break; } } catch (Exception exception) { // End with exception. this.State = -2; // -2 is end. this.ResultToReturn.SetException(exception); } } /// <summary> /// Configures the state machine with a heap-allocated replica. /// </summary> /// <param name="stateMachine">The heap-allocated replica.</param> [DebuggerHidden] public void SetStateMachine(IAsyncStateMachine stateMachine) // IAsyncStateMachine member. { // No core logic. } } Only Task and TaskCompletionSource are involved in this version. And MultiCallMethodAsync() can be simplified to: [DebuggerStepThrough] [AsyncStateMachine(typeof(MultiCallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { MultiCallMethodAsyncStateMachine multiCallMethodAsyncStateMachine = new MultiCallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Arg2 = arg2, Arg3 = arg3, ResultToReturn = new TaskCompletionSource<int>(), // -1: Begin // 0: 1st await is done // 1: 2nd await is done // ... // -2: End State = -1 }; multiCallMethodAsyncStateMachine.MoveNext(); // Original code are moved into this method. return multiCallMethodAsyncStateMachine.ResultToReturn.Task; } Now the whole state machine becomes very clean - it is about callback: Original code are split into pieces by “await”s, and each piece is put into each “case” in the state machine. Here the 2 awaits split the code into 3 pieces, so there are 3 “case”s. The “piece”s are chained by callback, that is done by Builder.AwaitUnsafeOnCompleted(callback), or currentTaskToAwait.ContinueWith(callback) in the simplified code. A previous “piece” will end with a Task (which is to be awaited), when the task is done, it will callback the next “piece”. The state machine’s state works with the “case”s to ensure the code “piece”s executes one after another. Callback If we focus on the point of callback, the simplification  can go even further – the entire state machine can be completely purged, and we can just keep the code inside MoveNext(). Now MultiCallMethodAsync() becomes: internal static Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { TaskCompletionSource<int> taskCompletionSource = new TaskCompletionSource<int>(); try { // Oringinal code begins. HelperMethods.Before(); MethodAsync(arg0, arg1).ContinueWith(await1 => { int resultOfAwait1 = await1.Result; HelperMethods.Continuation1(resultOfAwait1); MethodAsync(arg2, arg3).ContinueWith(await2 => { int resultOfAwait2 = await2.Result; HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; // Oringinal code ends. taskCompletionSource.SetResult(resultToReturn); }); }); } catch (Exception exception) { taskCompletionSource.SetException(exception); } return taskCompletionSource.Task; } Please compare with the original async / await code: HelperMethods.Before(); int resultOfAwait1 = await MethodAsync(arg0, arg1); HelperMethods.Continuation1(resultOfAwait1); int resultOfAwait2 = await MethodAsync(arg2, arg3); HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; return resultToReturn; Yeah that is the magic of C# async / await: Await is not to wait. In a await expression, a Task object will be return immediately so that execution is not blocked. The continuation code is compiled as that Task’s callback code. When that task is done, continuation code will execute. Please notice that many details inside the state machine are omitted for simplicity, like context caring, etc. If you want to have a detailed picture, please do check out the source code of AsyncTaskMethodBuilder and TaskAwaiter.

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  • Oracle Tutor: *** CAUTION to Word .docx Users ***

    - by [email protected]
    Microsoft released a security update KB969604 for Office 2007 (around June 2009) This update causes document variables within Word docx files to be scrambled. This update might still be pushed out via Office 2007 updates DO NOT save files as docx using MS OFFICE 2007 until you apply the MS hotfix # 970942 available here If you are using Windows XP with Office 2003 or Office 2000 and have installed an older Office 2007 compatibility pack, documents saved as docx may also cause the scrambled document variables. Installing the 2007 compatibility pack published on 1/6/2010 (version 4) will prevent the document variables from becoming corrupt. Those on Windows 2000 may not be able to install the latest compatibility pack, or the compatibility pack may not function properly. This situation will hopefully be rectified in the coming months. What is a document variable? Document variables store data inside the document, invisible to the user. The Tutor software uses them when converting the document to HTML and when creating the flowchart, just to name a couple of uses. How will you know if a document's variables are scrambled? The difficulty in diagnosing the issue is that the symptoms can take myriad forms. There isn't a single error message or a single feature that one can point to and say, "test for the problem by doing this." The best clue about the error is seeing any kind of string in an error message that has garbage characters, question marks, xml code snippets, or just nonsense. Such as "Language ?????????????xlr;lwlerkjl could not be found." It is also possible to see the corrupted data in the footers of the Word docs. And, just because the footers look correct does not mean that the document variables are not corrupted. The corruption problem does not occur in every document variable in the document, just some of them. Often it is less than a quarter of them. What is the difference between docx files and doc files? Office 2007 uses Office Open XML formats with .docx and .docm filename extensions. - Docx is an Office Open XML word document. - Docm is a macro enabled Office Open XML document. This means the file structure behind the scenes is quite different from the binary file formats used prior to Office 2007 such as .doc, .dot, .xls, and .ppt. Solution Summary: For Windows XP and Word 2007: Install the hotfix, or save files as *.doc For Windows XP and Word 2000 and 2003: Install the latest compatibility pack or save files as *.doc For Windows 2000 with Word 2000 or 2003, do not use any compatibility pack, save files as *.doc Emily Chorba Principle Product Manager for Oracle Tutor

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  • Is reliance on parametrized queries the only way to protect against SQL injection?

    - by Chris Walton
    All I have seen on SQL injection attacks seems to suggest that parametrized queries, particularly ones in stored procedures, are the only way to protect against such attacks. While I was working (back in the Dark Ages) stored procedures were viewed as poor practice, mainly because they were seen as less maintainable; less testable; highly coupled; and locked a system into one vendor; (this question covers some other reasons). Although when I was working, projects were virtually unaware of the possibility of such attacks; various rules were adopted to secure the database against corruption of various sorts. These rules can be summarised as: No client/application had direct access to the database tables. All accesses to all tables were through views (and all the updates to the base tables were done through triggers). All data items had a domain specified. No data item was permitted to be nullable - this had implications that had the DBAs grinding their teeth on occasion; but was enforced. Roles and permissions were set up appropriately - for instance, a restricted role to give only views the right to change the data. So is a set of (enforced) rules such as this (though not necessarily this particular set) an appropriate alternative to parametrized queries in preventing SQL injection attacks? If not, why not? Can a database be secured against such attacks by database (only) specific measures? EDIT Emphasis of the question changed slightly, in the light of the initial responses received. Base question unchanged. EDIT2 The approach of relying on paramaterized queries seems to be only a peripheral step in defense against attacks on systems. It seems to me that more fundamental defenses are both desirable, and may render reliance on such queries not necessary, or less critical, even to defend specifically against injection attacks. The approach implicit in my question was based on "armouring" the database and I had no idea whether it was a viable option. Further research has suggested that there are such approaches. I have found the following sources that provide some pointers to this type of approach: http://database-programmer.blogspot.com http://thehelsinkideclaration.blogspot.com The principle features I have taken from these sources is: An extensive data dictionary, combined with an extensive security data dictionary Generation of triggers, queries and constraints from the data dictionary Minimize Code and maximize data While the answers I have had so far are very useful and point out difficulties arising from disregarding paramaterized queries, ultimately they do not answer my original question(s) (now emphasised in bold).

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  • Cloning a dual boot system from HDD to SSD

    - by Alex
    I'm planning on replacing my laptop's HDD with a 256GB SSD, but I have a dual-boot (12.04 and Windows 7) setup and I'd like to be able to directly migrate Ubuntu over without having to reinstall and lose all of my settings. GParted reports the following partition setup on my HDD. I am, of course, able to modify it if necessary. /dev/sda1 (NTFS) 66.92 out of 200.00 MB used I'm honestly not sure what this partition is for. Maybe for Windows 7 system files? I'm hesitant to mess with it. (edit; it turns out it is a partition for Windows recovery files in the event of OS corruption, so I don't want to remove it. Plus it also appears to be a major pain to remove anyways) /dev/sda2 (NTFS) 116.35 out of 339.06 GB used (boot) This partition is the C:/ drive on my Windows installation. I don't use it on my Ubuntu installation, except it is the boot partition and thus has grub on it. /dev/sda4 (extended) > /dev/sda5 (ext4) 14.49 out of 91.34 GB used > /dev/sda6 (linux-swap) 5.92 GB These are my Ubuntu partitions. /sda5 contains my documents and all of the files I use on Ubuntu, and (as far as I know) the system files for Ubuntu itself (it's the partition I created when prompted by the Live-DVD installer). /sda6 is, of course, the swap partition which I only need for hibernation (6GB of RAM). /dev/sda3 (NTFS) 9.89 out of 14.75 GB used This is an annoying partition that Lenovo created to store some drivers and files that I might need later on. For example, it allows me to use OneKeyRecovery for a quick factory recovery if absolutely necessary, not sure if that'll work on an SSD. It also contains not-so-important files for bloatware installation. In total, my HDD only has about 150GB of files on it so it should fit comfortably on the SSD. The problem is, I want to exactly migrate my files, partitions, OSes, MBR, etc. from my HDD to my SSD and I'm not quite sure how to do this. I've seen CloneZilla referenced before, but I'm not all too experienced and the documentation for it quite frankly seems a bit like a foreign language to me. So, put simply, is there any way I can exactly clone this HDD to an SSD without a massive headache? Also, if it matters, I'll probably be using an external hard drive case (as recommended in online tutorials) to externally attach the SSD to my laptop during the cloning process due to the lack of two hard drive slots in the machine.

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  • Manic Monday - More OpenWorld Solaris Sessions: Developers, Cloud, Customer Insights, Hardware Optimization

    - by Larry Wake
    We're overflowing with Monday sessions; literally more than one person can take in. Learn more about what's new in Oracle Solaris Studio, hear about the latest x86 and SPARC hardware optimizations, get some insights on cloud deployment strategies, and find out from your peers what they're doing with Oracle Solaris. If you're an OpenWorld attendee, go to to Schedule Builder to guarantee your space in any session or lab. See yesterday's blog post and the "Focus on Oracle Solaris" guide for even more sessions. Monday, October 1st: 10:45 AM - Maximizing Your SPARC T4 Oracle Solaris Application Performance(CON6382,  Marriott Marquis - Golden Gate C3) Hear how customers and commercial software partners have reached peak performance on SPARC T4 servers and engineered systems with Oracle Solaris Studio and its latest tools for analyzing, reporting, and improving runtime performance: Autoparallelizing, high-performance compilers Performance Analyzer (used to find performance hotspots) Thread Analyzer (to expose data races and deadlocks) Code Analyzer (used to discover latent memory corruption issues) 10:45 Cloud Formation: Implementing IaaS in Practice with Oracle Solaris(CON8787, Moscone South 302) Decisions, decisions--at the same time, we've got a session that covers why Oracle Solaris is the ideal OS for public or private clouds, IaaS or PaaS, with built-in features for elastic infrastructure, unrivaled security, superfast installation and deployment, nonstop availability, and crystal-clear observability. This session will include a customer study on how Oracle Solaris is used in the cloud today to implement the Oracle stack. 12:15 PM - Customer Insight: Oracle Solaris on Oracle Exadata, Oracle Exalogic, and SPARC SuperCluster(CON8760, Moscone South 270) Hear from customers what benefits they have realized from using the Oracle stack on Oracle Exadata and Oracle’s SPARC SuperCluster and from using Oracle Solaris on those engineered systems, taking advantage of built-in lightweight OS virtualization (Zones), enterprise reliability and scale, and other key features. 1:45 PM - Case Study: Mobile Tornado Uses Oracle Technology for Better RAS and TCO?(CON4281, Moscone West 2005) Mobile Tornado develops and markets instant communication platforms, replacing traditional radio networks with cellular networks. Its critical concern is uptime. Find out how they've used Oracle Solaris, Netra SPARC T4, and Oracle Solaris Cluster, including Oracle Solaris ZFS and Zones, for their Oracle Database deployments to improve reliability and drive down cost. 3:15 PM - Technical Panel: Developing High Performance Applications on Oracle Solaris(CON7196, Marriott Marquis - Golden Gate C2) Engineers from the Oracle Solaris, Oracle Database, and Oracle Tuxedo development teams, and Oracle ISV Engineering discuss how they develop high-performance enterprise applications that take advantage of Oracle's SPARC and x86 servers, with Oracle Solaris Studio and new Oracle Solaris 11 features. Topics will include developer tools, parallel frameworks, best practices, and methodologies, as well as insights and case studies on parallelizing and optimizing application performance on Oracle Solaris. Bring your best questions! 3:15 PM -  x86 Power Management with Oracle Solaris: Current State, Opportunities, and Future(CON6271, Moscone West 2012) Another option for this time slot: learn about how Intel Xeon and Oracle Solaris work together to reduce server power consumption. This presentation addresses some of the recent power management improvements in Oracle Solaris, opportunities to further improve energy efficiency, and some future directions for Oracle Solaris power management.

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  • Fail to start windows after Ubuntu 11.10 install

    - by user49995
    Computer: HP Pavilion dv7-6140eo OS: Originally Win7 I recently decided to try out Ubuntu, and I decided to dual-boot it with Windows 7. First I googled some how-to's, then I downloaded Ubuntu onto a memory stick and made a second partition (I originally only had one partition that I shrunk and used the unallocated space to install onto during the Ubuntu install). During the install I set format type to xt4 (or something, it was the default option), chose the "in the beginning" option and set the last option as "\". The install was successful. Although, when I restarted my computer I weren't able to choose which operating system to start; it went right into windows. After showing the windows logo for half a second before rebooting, I get a blue screen (see bottom of the page). Trying to fix it, I deleted the newly made partition I had just installed Ubuntu onto (seeing it wasn't working either). This made no difference. I proceeded with installing Ubuntu again, so I would at least have a functioning computer, and now Ubuntu works fine (on it now). The only difference on start-up is that I get a Grub window asking me to between several options including Linux and Windows 7 (loader). Now, if I choose Windows 7, I get the message "Windows was unable to start. A recent software or hardware change might be the cause". It recommends me to choose the first option of the two it provides; to start start-up repair tool. The second option being starting windows normally. If I start windows normally, the same thing happens as earlier. My computer does not have a windows installation CD. Although, it has (at least it used to, if I haven't screwed that too up) a 17gb recovery partition. In addition I made an image of the computer onto a external hard drive when I first got it. Though, I have no idea how to use either. If anyone has any idea how I can make windows work again or reinstall it (already backed up my files) it would be greatly appreciated. I still prefer to dual boot between the two functioning operating systems, but I will settle for a functioning windows 7. Thanks a lot for any replies. Blue screen: A problem has been detected and Windows has been shut down to prevent damage to your computer. If this is the first time you've seen this Stop error screen, restart your computer. If this screen appears again, follow these steps: Check for viruses on your computer. Remove and newly installed hard drives or hard drive controllers. Check your hard drive to make sure it is properly configures and terminated. Run CMKDSK /F to check for hard drive corruption, and then restart your computer. Technical information: **STOP: 0x0000007B (0xFFFFF880009A97E8,0xFFFFFFFFC0000034, 0x0000000000000000,0x0000000000000000

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  • Block-level deduplicating filesystem

    - by James Haigh
    I'm looking for a deduplicating copy-on-write filesystem solution for general user data such as /home and backups of it. It should use online/inline/synchronous deduplication at the block-level using secure hashing (for negligible chance of collisions) such as SHA256 or TTH. Duplicate blocks need not even touch the disk. The idea is that I should be able to just copy /home/<user> to an external HDD with the same such filesystem to do a backup. Simple. No messing around with incremental backups where corruption to any of the snapshots will nearly always break all later snapshots, and no need to use a specific tool to delete or 'checkout' a snapshot. Everything should simply be done from the file browser without worry. Can you imagine how easy this would be? I'd never have to think twice about backing-up again! I don't mind a performance hit, reliability is the main concern. Although, with specific implementations of cp, mv and scp, and a file browser plugin, these operations would be very fast, especially when there is a lot of duplication as they would only need to transfer the absent blocks. Accidentally using conventional copy tools that do not integrate with the FS would merely take longer, waste some bandwidth when copying remotely and waste some CPU, as the duplicate data would be re-read, re-transferred and re-hashed (although nothing would be re-written), but would absolutely not corrupt anything. (Some filesharing software may also be able to benefit by integrating with the FS.) So what's the best way of doing this? I've looked at some options: lessfs - Looks unmaintained. Any good? [Opendedup/SDFS][3] - Java? Could I use this on Android?! What does [SDFS][4] stand for? [Btrfs][5] - Some patches floating around on mailing list archives, but no real support. [ZFS][6] - Hopefully they'll one day relicense under a true Free/Opensource GPL-compatible licence. Also, 2 years ago I had a go at an attempt in Python using Fuse at the file-level to be used over the top of a typical solid FS such as EXT4, but I found Fuse for Python underdocumented and didn't manage to implement all of the system calls. My first post here, so I can't post more than 2 links until I get over 10 rep: [3]: http://www.opendedup.org/ [4]: https://en.wikipedia.org/w/index.php?title=SDFS&action=edit&redlink=1 [5]: https://en.wikipedia.org/wiki/Btrfs#Features [6]: https://en.wikipedia.org/wiki/ZFS#Linux

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  • Working with Windows and Unix

    - by user554629
    Beware of new line characters One of the most frequent issues we encounter in Tech Support is the corruption of files that are transferred between Windows and Unix.   The transfer can occur at any stage, but ultimately involves a transfer of a file using an ftp client that is running on Windows;  it could be ftp or filezilla. Windows uses two characters to mark the end of a line in a text file (CR/LF),carriage return, linefeed.   Unix uses a single character (CR). In all situations, it is best to use binary mode transfer for all files, including ascii text files. Common problems: upload a core file from unix to windows using ftp in ascii mode.The file is going to be larger on Windows than Unix.ftp doesn't know if this is a text file with real line-ends, it takes every ascii CR and transmits two ascii characters CR/LF.The core file, tar file, library ... will be corrupted when transferred to Oracle. download a shell script to Windows, and transfer it to Unix using ftpIf the file is edited on Windows, the unix script line-end chars will be doubled.Unix doesn't know how to handle that, and will likely tell you the script is not executable.Why?  The first line of a shell script ( called "sh-bang" ), identifies the command interpreter the unix shell should use for this script.   Common examples:#/bin/sh#/bin/ksh#/bin/bash#/bin/perl#/bin/sh^M    # will not be understood.#/bin/env ksh # special syntax.  Find ksh and run it dos2unix is a common utility found on most unix platforms, that repairs the issue of Windows LineEnd characters in unix script files.   I've written my own flavor of this utility for use in Tech Support and build environments, that is a bit easier to use, and has some nice side-effects. accepts a list of files:   dos2unix *.sh repairs the file in-place.  Doesn't generate a new file you have to name retains the same timestamp;  it is the encoding that changed, not the file content. Here are the versions of dos2unix for each of the environments we work in.They are compressed with gzip, to avoid the ftp ascii transfer trap,and because I am quite limited in the number of files I can upload to this blog. AIX Linux Solaris sparc  Windows 

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