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• Adding more OR searches with CONTAINS Brings Query to Crawl

  - by scolja

  I have a simple query that relies on two full-text indexed tables, but it runs extremely slow when I have the CONTAINS combined with any additional OR search. As seen in the execution plan, the two full text searches crush the performance. If I query with just 1 of the CONTAINS, or neither, the query is sub-second, but the moment you add OR into the mix the query becomes ill-fated. The two tables are nothing special, they're not overly wide (42 cols in one, 21 in the other; maybe 10 cols are FT indexed in each) or even contain very many records (36k recs in the biggest of the two). I was able to solve the performance by splitting the two CONTAINS searches into their own SELECT queries and then UNION the three together. Is this UNION workaround my only hope? Thanks. SELECT a.CollectionID FROM collections a INNER JOIN determinations b ON a.CollectionID = b.CollectionID WHERE a.CollrTeam_Text LIKE '%fa%' OR CONTAINS(a.*, '"*fa*"') OR CONTAINS(b.*, '"*fa*"') Execution Plan (guess I need more reputation before I can post the image):

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• How to change size of STL container in C++

  - by Jaime Pardos

  I have a piece of performance critical code written with pointers and dynamic memory. I would like to rewrite it with STL containers, but I'm a bit concerned with performance. Is there a way to increase the size of a container without initializing the data? For example, instead of doing ptr = new BYTE[x]; I want to do something like vec.insert(vec.begin(), x, 0); However this initializes every byte to 0. Isn't there a way to just make the vector grow? I know about reserve() but it just allocates memory, it doesn't change the size of the vector, and doesn't allows me to access it until I have inserted valid data. Thank you everyone.

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• When accessing ResultSets in JDBC, is there an elegant way to distinguish between nulls and actual z

  - by Uri

  When using JDBC and accessing primitive types via a result set, is there a more elegant way to deal with the null/0 than the following: int myInt = rs.getInt(columnNumber) if(rs.wasNull())? { // Treat as null } else { // Treat as 0 } I personally cringe whenever I see this sort of code. I fail to see why ResultSet was not defined to return the boxed integer types (except, perhaps, performance) or at least provide both. Bonus points if anyone can convince me that the current API design is great :) My solution was to write a wrapper that returns an Integer (I care more about elegance of client code than performance), but I'm wondering if I'm missing a better way to do this.

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• List filtering: list comprehension vs. lambda + filter

  - by Agos

  I happened to find myself having a basic filtering need: I have a list and I have to filter it by an attribute of the items. My code looked like this: list = [i for i in list if i.attribute == value] But then i thought, wouldn't it be better to write it like this? filter(lambda x: x.attribute == value, list) It's more readable, and if needed for performance the lambda could be taken out to gain something. Question is: are there any caveats in using the second way? Any performance difference? Am I missing the Pythonic Way™ entirely and should do it in yet another way (such as using itemgetter instead of the lambda)? Thanks in advance

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• Using Lambda Statements for Event Handlers

  - by lush

  I currently have a page which is declared as follows: public partial class MyPage : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { //snip MyButton.Click += (o, i) => { //snip } } } I've only recently moved to .NET 3.5 from 1.1, so I'm used to writing event handlers outside of the Page_Load. My question is; are there any performance drawbacks or pitfalls I should watch out for when using the lambda method for this? I prefer it, as it's certainly more concise, but I do not want to sacrifice performance to use it. Thanks.

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• Clustered index on frequently changing reference table of one or more foreign keys

  - by Ian

  My specific concern is related to the performance of a clustered index on a reference table that has many rapid inserts and deletes. Table 1 "Collection" collection_pk int (among other fields) Table 2 "Item" item_pk int (among other fields) Reference Table "Collection_Items" collection_pk int, item_pk int (combined primary key) Because the primary key is composed of both pks, a clustered index is created and the data physically ordered in the table according to the combined keys. I have many users creating and deleting collections and adding and removing items to those collections very frequently affecting the "Collection_Items" table, and its clustered index. QUESTION PART: Since the "Collection_Items" table is so dynamic, wouldn't there be a big performance hit on constantly resorting the table rows because of the clustered index ? If yes, what should I do to minimize this ?

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• Controlling access to large files in Apache

  - by obeattie

  Hi there, I am looking to control access to some large files (we're talking many GB here) by the use of signed URLs. The files are currently restricted by LDAP Basic authentication (mod_auth_ldap), but I need to change this to verify the signature (passed as a query parameter in the URL). Basically, I just need to run a script to verify the signature, and allow the request to proceed as if authentication had succeeded. My initial thought to this was just to use a simple CGI script, but as the files are so large I'm concerned about performance. So, really, this question is (probably) more like "are there any performance implications of streaming large files from a CGI script via Apache?"… and if so, "is there a better way of doing this (short of writing a dedicated authentication module)?" If this makes any sense, help would be much appreciated :) P.S. I wasn't sure exactly what to search for for this (10 minutes of Googling were fruitless), so I may very well be duplicating someone else's post.

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• Javascript large number array compression

  - by gatapia

  Hi All, I've got a javascript application that sends a large amount of numerical data down the wire. This data is then stored in a database. I am having size issues (too much bandwidth, database getting too big). I am now ready to sacrifice some performance for compression. I was thinking of implementing a base 62 number.toString(62) and parseInt(compressed, 62). This would certainly reduce the size of the data but before I go ahead and do this I thought I would put it to the folks here as I know there must be some outside the box solution I have not considered. The basic specs are: - Compress large number arrays into strings for JSONP transfer (So I think UTF is out) - Be relatively fast, look I'm not expecting same performance as I have now but I also don't want gzip compression either. Any ideas would be greatly appreciated. Thanks Guido Tapia

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• Checking exception before using GETITEMBYID()

  - by ps123

  Hello, I am getting item by getiembyid...but I want to check before using it that whether item exist or not...I don't want to use query as main purpose of using Getitembyid is performance.....any idea how to achieve this... itemid = Response.QueryString["loc"]; SPList mylist = myweb.GetList(SPUrlUtility.CombineUrl(myweb.ServerRelativeUrl, "/Lists/Location")); //now id itemid does not exist it throws exception...so i want to check before using following statement that itemid exist...I know i can check throw SPQuery but as i said above because of performance issue only i m using itemid.... SPListItem myitem = mylist.GetItemById(Convert.ToInt32(itemid)); Any idea how to achieve this?

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• Video chat application : Which technology to choose ?

  - by WarDoGG

  I have to undertake a project which is to make a video chat application. The video has to be streamed from one location and can be viewed by multiple people spread out over the globe. Performance is really an issue and a delay of more than 2-3 seconds is unacceptable. From what i gather, this can be done in Flex and also in JAVA. Any performance issues and caveats with a particular approach ? I would really like the pros to comment on this and guide me through. Will be very very helpful. Are there any open source libraries available for video recording in flash / JAVA which i can integrate into my app and customize according to my needs ?

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• Benchmark of Java Try/Catch Block

  - by hectorg87

  I know that going into a catch block has some significance cost when executing a program, however, I was wondering if entering a try{} block also had any impact so I started looking for an answer in google with many opinions, but no benchmarking at all. Some answers I found were: Java try/catch performance, is it recommended to keep what is inside the try clause to a minimum? Try Catch Performance Java Java try catch blocks However they didn't answer my question with facts, so I decided to try it for myself. Here's what I did. I have a csv file with this format: host;ip;number;date;status;email;uid;name;lastname;promo_code; where everything after status is optional and will not even have the corresponding ; , so when parsing a validation has to be done to see if the value is there, here's where the try/catch issue came to my mind. The current code that in inherited in my company does this: StringTokenizer st=new StringTokenizer(line,";"); String host = st.nextToken(); String ip = st.nextToken(); String number = st.nextToken(); String date = st.nextToken(); String status = st.nextToken(); String email = ""; try{ email = st.nextToken(); }catch(NoSuchElementException e){ email = ""; } and it repeats what it's done for email with uid, name, lastname and promo_code. and I changed everything to: if(st.hasMoreTokens()){ email = st.nextToken(); } and in fact it performs faster. When parsing a file that doesn't have the optional columns. Here are the average times: --- Trying:122 milliseconds --- Checking:33 milliseconds however, here's what confused me and the reason I'm asking: When running the example with values for the optional columns in all 8000 lines of the CSV, the if() version still performs better than the try/catch version, so my question is Does really the try block does not have any performance impact on my code? The average times for this example are: --- Trying:105 milliseconds --- Checking:43 milliseconds Can somebody explain what's going on here? Thanks a lot

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• What is the best solution to replace a new memory allocator in an existing code?

  - by O. Askari

  During the last few days I've gained some information about memory allocators other than the standard malloc(). There are some implementations that seem to be much better than malloc() for applications with many threads. For example it seems that tcmalloc and ptmalloc have better performance. I have a C++ application that uses both malloc and new operators in many places. I thought replacing them with something like ptmalloc may improve its performance. But I wonder how does the new operator act when used in C++ application that runs on Linux? Does it use the standard behavior of malloc or something else? What is the best way to replace the new memory allocator with the old one in the code? Is there any way to override the behavior or new and malloc or do I need to replace all the calls to them one by one?

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• Is there any harm in running session_start() multiple times as the page request is being built (in p

  - by sprugman

  Presumably there's some tiny performance hit, but beyond that?

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• Marvell C++ compiler (for Windows CE) for building Qt

  - by vnm

  Hello, I was able to build Qt 4.5 for Windows CE (ARM4VI) using MS VisualC++ compiler. Now, I am trying to compile Qt 4.5 for Windows CE 5.0 using Marvel C++ compiler v 2.2 (former Intel C++ compiler for XScale architecture) for achieving some performance benefit. It seems, that this compiler not officially supported for building Qt by trolltech (no appropriate mkspec in mkspec's folder of Qt folder). So, my questions: Is it worth to trying build Qt by this compiler for achieving performance enhancement ? Is there any way for building Qt using Marvell C++ compiler (by creating my own mkspec or something like that)?

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• mysql twitter/facebook like status feed

  - by barjonah

  Hi, I have two tables. One named status like this... user_id | status --------+----------- 1 | random status from user 1 2 | random status from user 2 3 | random message from user 3 4 | staus from user 4 1 | second status for user1 etc... and another named users_following like this... user_id | is_following --------+----------- 1 | 2 1 | 3 2 | 1 3 | 2 meaning that user 1 is following both users 2 and 3 etc... So, let's say I chose user 1. What is the best query (performance wise) to show the status updates of users that user 1 is following, in this case users 2 and 3 currently I have something like SELECT * from status WHERE user_id IN(SELECT is_following FROM users_following WHERE user_id='1') LIMIT 0,5 but I don't think this is good for performance if a user was following thousands+ of users

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• which is better, creating a view or a new table?

  - by Carson

  I have some demanding mysql queries that are needed to grap same datasets from several mysql tables. I am thinking of creating a table or view to gather all demanding columns from other tables, so as to increase performance. If I create that table, I may need to do extra insert / update / delete operation each time other tables updated. if I create view, I am worrying if the performance can be greatly improved. Because data from other tables are changing very frequently. Most likely, the view may need to be created first everytime before selecting it. Any ideas? e.g. how to cache? other extra measures I can do?

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• How expensive are method calls in .net

  - by Andrew

  What is the relative performance cost of calling a method over in-line code?

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• How would I benchmark an Android Application?

  - by davs

  How would I benchmark or profile the performance of an Android application?

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• Sql Server as logging, best connection practise

  - by ozz

  I'm using SqlServer as logging. Yes this is wrong decision, there are better dbs for this requirement. But I have no other option for now. Logging interval is 3 logs per second. So I've static Logger class and it has static Log method. Using "Open Connection" as static member is better for performance. But what is the best implemantation of it? This is not that I know. public static class OzzLogger { static SqlConnection Con; static OzzLogger() { Con=ne SqlConnection(....); Con.Open(); } public static void Log(....) { Con.ExecuteSql(......); } } UPDATE I asked because of my old information. People say "connection pooling performance is enough". If there is no objection I'm closing the issue :)

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• Why is numpy c extension slow?

  - by Bitwise

  I am working on large numpy arrays, and some native numpy operations are too slow for my needs (for example simple operations such as "bitwise" A&B). I started looking into writing C extensions to try and improve performance. As a test case, I tried the example given here, implementing a simple trace calculation. I was able to get it to work, but was surprised by the performance: for a (1000,1000) numpy array, numpy.trace() was about 1000 times faster than the C extension! This happens whether I run it once or many times. Is this expected? Is the C extension overhead that bad? Any ideas how to speed things up?

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• C and C++: Array element access pointer vs int

  - by begun

  Is there a performance difference if you either do myarray[ i ] or store the adress of myarray[ i ] in a pointer?

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• How do you visualize difference between O(log n) and O(n log n)?

  - by Passionate programmer

  Binary search has a average case performance as O(log n) and Quick Sort with O(n log n) is O(n log n) is same as O(n) + O(log n)

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• Javascript === vs == : Does it matter which "equal" operator I use?

  - by bcasp

  I'm using JSLint to go through some horrific JavaScript at work and it's returning a huge number of suggestions to replace == with === when doing things like comparing 'idSele_UNVEHtype.value.length == 0' inside of an if statement. I'm basically wondering if there is a performance benefit to replacing == with ===. Any performance improvement would probably be welcomed as there are hundreds (if not thousands) of these comparison operators being used throughout the file. I tried searching for relevant information to this question, but trying to search for something like '=== vs ==' doesn't seem to work so well with search engines...

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• What is the best way to partition large tables in SQL Server?

  - by RyanFetz

  In a recent project the "lead" developer designed a database schema where "larger" tables would be split across two seperate databases with a view on the main database which unioned the two seperate database-tables together. The main database is what the application was driven off of so these tables looked and felt like ordinary tables (except some quirkly things around updating). This seemed like a HUGE performance problem. We do see problems with performance around these tables but nothing to make him change his mind about his design. Just wondering what is the best way to do this, or if it is even worth doing?

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• Does the order of the columns in a SELECT statement make a difference?

  - by Frank Computer

  This question was inspired by a previous question posted on SO, "Does the order of the WHERE clause make a differnece?". Would it improve a SELECT statement's performance if the the columns used in the WHERE section are placed at the begining of the SELECT statement? example: SELECT customer.id, transaction.id, transaction.efective_date, transaction.a, [...] FROM customer, transaction WHERE customer.id = transaction.id; I do know that limiting the list of columns to only the needed ones in a SELECT statement improves performance as opposed to using SELECT * because the current list is smaller.

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