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  • emacs does not open a file from argument and syntax highlight does not work

    - by Jus
    In my latest ubuntu box, When I type for example emacs ~/.bashrc, Emacs will start but not open .bashrc. This is true for any file I pass in. I've used Emacs for several years, and have never experienced this problem before. I added (global-font-lock-mode 1);; to my .emacs file, and Emacs does recognize it, for example. "(C++/; Abbrev)", but it won't do syntax highlighting. If you can solve any of these problems, it will be very appreciated. The following is my machine's configuration: uname -a Linux 2.6.35-28-generic-pae #49-Ubuntu SMP Tue Mar 1 14:58:06 UTC 2011 i686 GNU/Linux ~/.emacs (global-font-lock-mode 1);;

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  • DB Schema for ACL involving 3 subdomains

    - by blacktie24
    Hi, I am trying to design a database schema for a web app which has 3 subdomains: a) internal employees b) clients c) contractors. The users will be able to communicate with each other to some degree, and there may be some resources that overlap between them. Any thoughts about this schema? Really appreciate your time and thoughts on this. Cheers! -- -- Table structure for table locations CREATE TABLE IF NOT EXISTS locations ( id bigint(20) NOT NULL, name varchar(250) NOT NULL ) ENGINE=InnoDB DEFAULT CHARSET=latin1; -- -- Table structure for table privileges CREATE TABLE IF NOT EXISTS privileges ( id int(11) NOT NULL AUTO_INCREMENT, name varchar(255) NOT NULL, resource_id int(11) NOT NULL, PRIMARY KEY (id) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=10 ; -- -- Table structure for table resources CREATE TABLE IF NOT EXISTS resources ( id int(11) NOT NULL AUTO_INCREMENT, name varchar(255) NOT NULL, user_type enum('internal','client','expert') NOT NULL, PRIMARY KEY (id) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=3 ; -- -- Table structure for table roles CREATE TABLE IF NOT EXISTS roles ( id int(11) NOT NULL AUTO_INCREMENT, name varchar(255) NOT NULL, type enum('position','department') NOT NULL, parent_id int(11) DEFAULT NULL, user_type enum('internal','client','expert') NOT NULL, PRIMARY KEY (id) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=3 ; -- -- Table structure for table role_perms CREATE TABLE IF NOT EXISTS role_perms ( id int(11) NOT NULL AUTO_INCREMENT, role_id int(11) NOT NULL, privilege_id int(11) NOT NULL, mode varchar(250) NOT NULL, PRIMARY KEY (id) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=2 ; -- -- Table structure for table users CREATE TABLE IF NOT EXISTS users ( id int(10) unsigned NOT NULL AUTO_INCREMENT, email varchar(255) NOT NULL, password varchar(255) NOT NULL, salt varchar(255) NOT NULL, type enum('internal','client','expert') NOT NULL, first_name varchar(255) NOT NULL, last_name varchar(255) NOT NULL, location_id int(11) NOT NULL, phone varchar(255) NOT NULL, status enum('active','inactive') NOT NULL DEFAULT 'active', PRIMARY KEY (id) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=4 ; -- -- Table structure for table user_perms CREATE TABLE IF NOT EXISTS user_perms ( id int(11) NOT NULL AUTO_INCREMENT, user_id int(11) NOT NULL, privilege_id int(11) NOT NULL, mode varchar(250) NOT NULL, PRIMARY KEY (id) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=2 ; -- -- Table structure for table user_roles CREATE TABLE IF NOT EXISTS user_roles ( id int(11) NOT NULL, user_id int(11) NOT NULL, role_id int(11) NOT NULL ) ENGINE=InnoDB DEFAULT CHARSET=latin1;

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  • MySQL Database Query Problem

    - by moustafa
    I need your help!!!. I need to query a table in my database that has record of goods sold. I want the query to detect a particular product and also calculate the quantity sold. The product are 300 now, but it would increase in the future. Below is a sample of my DB Table #---------------------------- # Table structure for litorder #---------------------------- CREATE TABLE `litorder` ( `id` int(10) NOT NULL auto_increment, `name` varchar(50) NOT NULL default '', `address` varchar(50) NOT NULL default '', `xdate` date NOT NULL default '0000-00-00', `ref` varchar(20) NOT NULL default '', `code1` varchar(50) NOT NULL default '', `code2` varchar(50) NOT NULL default '', `code3` varchar(50) NOT NULL default '', `code4` varchar(50) NOT NULL default '', `code5` varchar(50) NOT NULL default '', `code6` varchar(50) NOT NULL default '', `code7` varchar(50) NOT NULL default '', `code8` varchar(50) NOT NULL default '', `code9` varchar(50) NOT NULL default '', `code10` varchar(50) NOT NULL default '', `code11` varchar(50) character set latin1 collate latin1_bin NOT NULL default '', `code12` varchar(50) NOT NULL default '', `code13` varchar(50) NOT NULL default '', `code14` varchar(50) NOT NULL default '', `code15` varchar(50) NOT NULL default '', `product1` varchar(100) NOT NULL default '0', `product2` varchar(100) NOT NULL default '0', `product3` varchar(100) NOT NULL default '0', `product4` varchar(100) NOT NULL default '0', `product5` varchar(100) NOT NULL default '0', `product6` varchar(100) NOT NULL default '0', `product7` varchar(100) NOT NULL default '0', `product8` varchar(100) NOT NULL default '0', `product9` varchar(100) NOT NULL default '0', `product10` varchar(100) NOT NULL default '0', `product11` varchar(100) NOT NULL default '0', `product12` varchar(100) NOT NULL default '0', `product13` varchar(100) NOT NULL default '0', `product14` varchar(100) NOT NULL default '0', `product15` varchar(100) NOT NULL default '0', `price1` int(10) NOT NULL default '0', `price2` int(10) NOT NULL default '0', `price3` int(10) NOT NULL default '0', `price4` int(10) NOT NULL default '0', `price5` int(10) NOT NULL default '0', `price6` int(10) NOT NULL default '0', `price7` int(10) NOT NULL default '0', `price8` int(10) NOT NULL default '0', `price9` int(10) NOT NULL default '0', `price10` int(10) NOT NULL default '0', `price11` int(10) NOT NULL default '0', `price12` int(10) NOT NULL default '0', `price13` int(10) NOT NULL default '0', `price14` int(10) NOT NULL default '0', `price15` int(10) NOT NULL default '0', `quantity1` int(10) NOT NULL default '0', `quantity2` int(10) NOT NULL default '0', `quantity3` int(10) NOT NULL default '0', `quantity4` int(10) NOT NULL default '0', `quantity5` int(10) NOT NULL default '0', `quantity6` int(10) NOT NULL default '0', `quantity7` int(10) NOT NULL default '0', `quantity8` int(10) NOT NULL default '0', `quantity9` int(10) NOT NULL default '0', `quantity10` int(10) NOT NULL default '0', `quantity11` int(10) NOT NULL default '0', `quantity12` int(10) NOT NULL default '0', `quantity13` int(10) NOT NULL default '0', `quantity14` int(10) NOT NULL default '0', `quantity15` int(10) NOT NULL default '0', `amount1` int(10) NOT NULL default '0', `amount2` int(10) NOT NULL default '0', `amount3` int(10) NOT NULL default '0', `amount4` int(10) NOT NULL default '0', `amount5` int(10) NOT NULL default '0', `amount6` int(10) NOT NULL default '0', `amount7` int(10) NOT NULL default '0', `amount8` int(10) NOT NULL default '0', `amount9` int(10) NOT NULL default '0', `amount10` int(10) NOT NULL default '0', `amount11` int(10) NOT NULL default '0', `amount12` int(10) NOT NULL default '0', `amount13` int(10) NOT NULL default '0', `amount14` int(10) NOT NULL default '0', `amount15` int(10) NOT NULL default '0', `totalNaira` double(20,0) NOT NULL default '0', `totalDollar` int(20) NOT NULL default '0', PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 COMMENT='InnoDB free: 4096 kB; InnoDB free: 4096 kB; InnoDB free: 409'; #---------------------------- # Records for table litorder #---------------------------- insert into litorder values (27, 'Sanyaolu Fisayo', '14 Adegboyega Street Palmgrove Lagos', '2010-05-31', '', 'DL 001', 'DL 002', 'DL 003', '', '', '', '', '', '', '', '', '', '', '', '', 'AILMENT & PREVENTION DVD- ENGLISH', 'AILMENT & PREVENTION DVD- HAUSA', 'BEAUTY CD', '', '', '', '', '', '', '', '', '', '', '', '', 800, 800, 3000, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 16, 16, 20, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 12800, 12800, 60000, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, '85600', 563), (28, 'Irenonse Esther', 'Lagos,Nigeria', '2010-06-01', '', 'DL 005', 'DL 008', 'FC 004', '', '', '', '', '', '', '', '', '', '', '', '', 'GET HEALTHY DVD', 'YOUR FUTURE DVD', 'FOREVER FACE CAP (YELLOW)', '', '', '', '', '', '', '', '', '', '', '', '', 1000, 900, 2000, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2000, 1800, 6000, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, '9800', 64), (29, 'Kalu Lekway', 'Lagos, Nigeria', '2010-06-01', '', 'DL 001', 'DL 003', '', '', '', '', '', '', '', '', '', '', '', '', '', 'AILMENT & PREVENTION DVD- ENGLISH', 'BEAUTY CD', '', '', '', '', '', '', '', '', '', '', '', '', '', 800, 3000, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2400, 18000, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, '20400', 133), (30, 'Dele', 'Ilupeju', '2010-06-02', '', 'DL 001', 'DL 003', '', '', '', '', '', '', '', '', '', '', '', '', '', 'AILMENT & PREVENTION DVD- ENGLISH', 'BEAUTY CD', '', '', '', '', '', '', '', '', '', '', '', '', '', 800, 3000, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10, 10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 8000, 30000, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, '38000', 250);

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  • Advanced TSQL Tuning: Why Internals Knowledge Matters

    - by Paul White
    There is much more to query tuning than reducing logical reads and adding covering nonclustered indexes.  Query tuning is not complete as soon as the query returns results quickly in the development or test environments.  In production, your query will compete for memory, CPU, locks, I/O and other resources on the server.  Today’s entry looks at some tuning considerations that are often overlooked, and shows how deep internals knowledge can help you write better TSQL. As always, we’ll need some example data.  In fact, we are going to use three tables today, each of which is structured like this: Each table has 50,000 rows made up of an INTEGER id column and a padding column containing 3,999 characters in every row.  The only difference between the three tables is in the type of the padding column: the first table uses CHAR(3999), the second uses VARCHAR(MAX), and the third uses the deprecated TEXT type.  A script to create a database with the three tables and load the sample data follows: USE master; GO IF DB_ID('SortTest') IS NOT NULL DROP DATABASE SortTest; GO CREATE DATABASE SortTest COLLATE LATIN1_GENERAL_BIN; GO ALTER DATABASE SortTest MODIFY FILE ( NAME = 'SortTest', SIZE = 3GB, MAXSIZE = 3GB ); GO ALTER DATABASE SortTest MODIFY FILE ( NAME = 'SortTest_log', SIZE = 256MB, MAXSIZE = 1GB, FILEGROWTH = 128MB ); GO ALTER DATABASE SortTest SET ALLOW_SNAPSHOT_ISOLATION OFF ; ALTER DATABASE SortTest SET AUTO_CLOSE OFF ; ALTER DATABASE SortTest SET AUTO_CREATE_STATISTICS ON ; ALTER DATABASE SortTest SET AUTO_SHRINK OFF ; ALTER DATABASE SortTest SET AUTO_UPDATE_STATISTICS ON ; ALTER DATABASE SortTest SET AUTO_UPDATE_STATISTICS_ASYNC ON ; ALTER DATABASE SortTest SET PARAMETERIZATION SIMPLE ; ALTER DATABASE SortTest SET READ_COMMITTED_SNAPSHOT OFF ; ALTER DATABASE SortTest SET MULTI_USER ; ALTER DATABASE SortTest SET RECOVERY SIMPLE ; USE SortTest; GO CREATE TABLE dbo.TestCHAR ( id INTEGER IDENTITY (1,1) NOT NULL, padding CHAR(3999) NOT NULL,   CONSTRAINT [PK dbo.TestCHAR (id)] PRIMARY KEY CLUSTERED (id), ) ; CREATE TABLE dbo.TestMAX ( id INTEGER IDENTITY (1,1) NOT NULL, padding VARCHAR(MAX) NOT NULL,   CONSTRAINT [PK dbo.TestMAX (id)] PRIMARY KEY CLUSTERED (id), ) ; CREATE TABLE dbo.TestTEXT ( id INTEGER IDENTITY (1,1) NOT NULL, padding TEXT NOT NULL,   CONSTRAINT [PK dbo.TestTEXT (id)] PRIMARY KEY CLUSTERED (id), ) ; -- ============= -- Load TestCHAR (about 3s) -- ============= INSERT INTO dbo.TestCHAR WITH (TABLOCKX) ( padding ) SELECT padding = REPLICATE(CHAR(65 + (Data.n % 26)), 3999) FROM ( SELECT TOP (50000) n = ROW_NUMBER() OVER (ORDER BY (SELECT 0)) - 1 FROM master.sys.columns C1, master.sys.columns C2, master.sys.columns C3 ORDER BY n ASC ) AS Data ORDER BY Data.n ASC ; -- ============ -- Load TestMAX (about 3s) -- ============ INSERT INTO dbo.TestMAX WITH (TABLOCKX) ( padding ) SELECT CONVERT(VARCHAR(MAX), padding) FROM dbo.TestCHAR ORDER BY id ; -- ============= -- Load TestTEXT (about 5s) -- ============= INSERT INTO dbo.TestTEXT WITH (TABLOCKX) ( padding ) SELECT CONVERT(TEXT, padding) FROM dbo.TestCHAR ORDER BY id ; -- ========== -- Space used -- ========== -- EXECUTE sys.sp_spaceused @objname = 'dbo.TestCHAR'; EXECUTE sys.sp_spaceused @objname = 'dbo.TestMAX'; EXECUTE sys.sp_spaceused @objname = 'dbo.TestTEXT'; ; CHECKPOINT ; That takes around 15 seconds to run, and shows the space allocated to each table in its output: To illustrate the points I want to make today, the example task we are going to set ourselves is to return a random set of 150 rows from each table.  The basic shape of the test query is the same for each of the three test tables: SELECT TOP (150) T.id, T.padding FROM dbo.Test AS T ORDER BY NEWID() OPTION (MAXDOP 1) ; Test 1 – CHAR(3999) Running the template query shown above using the TestCHAR table as the target, we find that the query takes around 5 seconds to return its results.  This seems slow, considering that the table only has 50,000 rows.  Working on the assumption that generating a GUID for each row is a CPU-intensive operation, we might try enabling parallelism to see if that speeds up the response time.  Running the query again (but without the MAXDOP 1 hint) on a machine with eight logical processors, the query now takes 10 seconds to execute – twice as long as when run serially. Rather than attempting further guesses at the cause of the slowness, let’s go back to serial execution and add some monitoring.  The script below monitors STATISTICS IO output and the amount of tempdb used by the test query.  We will also run a Profiler trace to capture any warnings generated during query execution. DECLARE @read BIGINT, @write BIGINT ; SELECT @read = SUM(num_of_bytes_read), @write = SUM(num_of_bytes_written) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; SET STATISTICS IO ON ; SELECT TOP (150) TC.id, TC.padding FROM dbo.TestCHAR AS TC ORDER BY NEWID() OPTION (MAXDOP 1) ; SET STATISTICS IO OFF ; SELECT tempdb_read_MB = (SUM(num_of_bytes_read) - @read) / 1024. / 1024., tempdb_write_MB = (SUM(num_of_bytes_written) - @write) / 1024. / 1024., internal_use_MB = ( SELECT internal_objects_alloc_page_count / 128.0 FROM sys.dm_db_task_space_usage WHERE session_id = @@SPID ) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; Let’s take a closer look at the statistics and query plan generated from this: Following the flow of the data from right to left, we see the expected 50,000 rows emerging from the Clustered Index Scan, with a total estimated size of around 191MB.  The Compute Scalar adds a column containing a random GUID (generated from the NEWID() function call) for each row.  With this extra column in place, the size of the data arriving at the Sort operator is estimated to be 192MB. Sort is a blocking operator – it has to examine all of the rows on its input before it can produce its first row of output (the last row received might sort first).  This characteristic means that Sort requires a memory grant – memory allocated for the query’s use by SQL Server just before execution starts.  In this case, the Sort is the only memory-consuming operator in the plan, so it has access to the full 243MB (248,696KB) of memory reserved by SQL Server for this query execution. Notice that the memory grant is significantly larger than the expected size of the data to be sorted.  SQL Server uses a number of techniques to speed up sorting, some of which sacrifice size for comparison speed.  Sorts typically require a very large number of comparisons, so this is usually a very effective optimization.  One of the drawbacks is that it is not possible to exactly predict the sort space needed, as it depends on the data itself.  SQL Server takes an educated guess based on data types, sizes, and the number of rows expected, but the algorithm is not perfect. In spite of the large memory grant, the Profiler trace shows a Sort Warning event (indicating that the sort ran out of memory), and the tempdb usage monitor shows that 195MB of tempdb space was used – all of that for system use.  The 195MB represents physical write activity on tempdb, because SQL Server strictly enforces memory grants – a query cannot ‘cheat’ and effectively gain extra memory by spilling to tempdb pages that reside in memory.  Anyway, the key point here is that it takes a while to write 195MB to disk, and this is the main reason that the query takes 5 seconds overall. If you are wondering why using parallelism made the problem worse, consider that eight threads of execution result in eight concurrent partial sorts, each receiving one eighth of the memory grant.  The eight sorts all spilled to tempdb, resulting in inefficiencies as the spilled sorts competed for disk resources.  More importantly, there are specific problems at the point where the eight partial results are combined, but I’ll cover that in a future post. CHAR(3999) Performance Summary: 5 seconds elapsed time 243MB memory grant 195MB tempdb usage 192MB estimated sort set 25,043 logical reads Sort Warning Test 2 – VARCHAR(MAX) We’ll now run exactly the same test (with the additional monitoring) on the table using a VARCHAR(MAX) padding column: DECLARE @read BIGINT, @write BIGINT ; SELECT @read = SUM(num_of_bytes_read), @write = SUM(num_of_bytes_written) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; SET STATISTICS IO ON ; SELECT TOP (150) TM.id, TM.padding FROM dbo.TestMAX AS TM ORDER BY NEWID() OPTION (MAXDOP 1) ; SET STATISTICS IO OFF ; SELECT tempdb_read_MB = (SUM(num_of_bytes_read) - @read) / 1024. / 1024., tempdb_write_MB = (SUM(num_of_bytes_written) - @write) / 1024. / 1024., internal_use_MB = ( SELECT internal_objects_alloc_page_count / 128.0 FROM sys.dm_db_task_space_usage WHERE session_id = @@SPID ) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; This time the query takes around 8 seconds to complete (3 seconds longer than Test 1).  Notice that the estimated row and data sizes are very slightly larger, and the overall memory grant has also increased very slightly to 245MB.  The most marked difference is in the amount of tempdb space used – this query wrote almost 391MB of sort run data to the physical tempdb file.  Don’t draw any general conclusions about VARCHAR(MAX) versus CHAR from this – I chose the length of the data specifically to expose this edge case.  In most cases, VARCHAR(MAX) performs very similarly to CHAR – I just wanted to make test 2 a bit more exciting. MAX Performance Summary: 8 seconds elapsed time 245MB memory grant 391MB tempdb usage 193MB estimated sort set 25,043 logical reads Sort warning Test 3 – TEXT The same test again, but using the deprecated TEXT data type for the padding column: DECLARE @read BIGINT, @write BIGINT ; SELECT @read = SUM(num_of_bytes_read), @write = SUM(num_of_bytes_written) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; SET STATISTICS IO ON ; SELECT TOP (150) TT.id, TT.padding FROM dbo.TestTEXT AS TT ORDER BY NEWID() OPTION (MAXDOP 1, RECOMPILE) ; SET STATISTICS IO OFF ; SELECT tempdb_read_MB = (SUM(num_of_bytes_read) - @read) / 1024. / 1024., tempdb_write_MB = (SUM(num_of_bytes_written) - @write) / 1024. / 1024., internal_use_MB = ( SELECT internal_objects_alloc_page_count / 128.0 FROM sys.dm_db_task_space_usage WHERE session_id = @@SPID ) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; This time the query runs in 500ms.  If you look at the metrics we have been checking so far, it’s not hard to understand why: TEXT Performance Summary: 0.5 seconds elapsed time 9MB memory grant 5MB tempdb usage 5MB estimated sort set 207 logical reads 596 LOB logical reads Sort warning SQL Server’s memory grant algorithm still underestimates the memory needed to perform the sorting operation, but the size of the data to sort is so much smaller (5MB versus 193MB previously) that the spilled sort doesn’t matter very much.  Why is the data size so much smaller?  The query still produces the correct results – including the large amount of data held in the padding column – so what magic is being performed here? TEXT versus MAX Storage The answer lies in how columns of the TEXT data type are stored.  By default, TEXT data is stored off-row in separate LOB pages – which explains why this is the first query we have seen that records LOB logical reads in its STATISTICS IO output.  You may recall from my last post that LOB data leaves an in-row pointer to the separate storage structure holding the LOB data. SQL Server can see that the full LOB value is not required by the query plan until results are returned, so instead of passing the full LOB value down the plan from the Clustered Index Scan, it passes the small in-row structure instead.  SQL Server estimates that each row coming from the scan will be 79 bytes long – 11 bytes for row overhead, 4 bytes for the integer id column, and 64 bytes for the LOB pointer (in fact the pointer is rather smaller – usually 16 bytes – but the details of that don’t really matter right now). OK, so this query is much more efficient because it is sorting a very much smaller data set – SQL Server delays retrieving the LOB data itself until after the Sort starts producing its 150 rows.  The question that normally arises at this point is: Why doesn’t SQL Server use the same trick when the padding column is defined as VARCHAR(MAX)? The answer is connected with the fact that if the actual size of the VARCHAR(MAX) data is 8000 bytes or less, it is usually stored in-row in exactly the same way as for a VARCHAR(8000) column – MAX data only moves off-row into LOB storage when it exceeds 8000 bytes.  The default behaviour of the TEXT type is to be stored off-row by default, unless the ‘text in row’ table option is set suitably and there is room on the page.  There is an analogous (but opposite) setting to control the storage of MAX data – the ‘large value types out of row’ table option.  By enabling this option for a table, MAX data will be stored off-row (in a LOB structure) instead of in-row.  SQL Server Books Online has good coverage of both options in the topic In Row Data. The MAXOOR Table The essential difference, then, is that MAX defaults to in-row storage, and TEXT defaults to off-row (LOB) storage.  You might be thinking that we could get the same benefits seen for the TEXT data type by storing the VARCHAR(MAX) values off row – so let’s look at that option now.  This script creates a fourth table, with the VARCHAR(MAX) data stored off-row in LOB pages: CREATE TABLE dbo.TestMAXOOR ( id INTEGER IDENTITY (1,1) NOT NULL, padding VARCHAR(MAX) NOT NULL,   CONSTRAINT [PK dbo.TestMAXOOR (id)] PRIMARY KEY CLUSTERED (id), ) ; EXECUTE sys.sp_tableoption @TableNamePattern = N'dbo.TestMAXOOR', @OptionName = 'large value types out of row', @OptionValue = 'true' ; SELECT large_value_types_out_of_row FROM sys.tables WHERE [schema_id] = SCHEMA_ID(N'dbo') AND name = N'TestMAXOOR' ; INSERT INTO dbo.TestMAXOOR WITH (TABLOCKX) ( padding ) SELECT SPACE(0) FROM dbo.TestCHAR ORDER BY id ; UPDATE TM WITH (TABLOCK) SET padding.WRITE (TC.padding, NULL, NULL) FROM dbo.TestMAXOOR AS TM JOIN dbo.TestCHAR AS TC ON TC.id = TM.id ; EXECUTE sys.sp_spaceused @objname = 'dbo.TestMAXOOR' ; CHECKPOINT ; Test 4 – MAXOOR We can now re-run our test on the MAXOOR (MAX out of row) table: DECLARE @read BIGINT, @write BIGINT ; SELECT @read = SUM(num_of_bytes_read), @write = SUM(num_of_bytes_written) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; SET STATISTICS IO ON ; SELECT TOP (150) MO.id, MO.padding FROM dbo.TestMAXOOR AS MO ORDER BY NEWID() OPTION (MAXDOP 1, RECOMPILE) ; SET STATISTICS IO OFF ; SELECT tempdb_read_MB = (SUM(num_of_bytes_read) - @read) / 1024. / 1024., tempdb_write_MB = (SUM(num_of_bytes_written) - @write) / 1024. / 1024., internal_use_MB = ( SELECT internal_objects_alloc_page_count / 128.0 FROM sys.dm_db_task_space_usage WHERE session_id = @@SPID ) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; TEXT Performance Summary: 0.3 seconds elapsed time 245MB memory grant 0MB tempdb usage 193MB estimated sort set 207 logical reads 446 LOB logical reads No sort warning The query runs very quickly – slightly faster than Test 3, and without spilling the sort to tempdb (there is no sort warning in the trace, and the monitoring query shows zero tempdb usage by this query).  SQL Server is passing the in-row pointer structure down the plan and only looking up the LOB value on the output side of the sort. The Hidden Problem There is still a huge problem with this query though – it requires a 245MB memory grant.  No wonder the sort doesn’t spill to tempdb now – 245MB is about 20 times more memory than this query actually requires to sort 50,000 records containing LOB data pointers.  Notice that the estimated row and data sizes in the plan are the same as in test 2 (where the MAX data was stored in-row). The optimizer assumes that MAX data is stored in-row, regardless of the sp_tableoption setting ‘large value types out of row’.  Why?  Because this option is dynamic – changing it does not immediately force all MAX data in the table in-row or off-row, only when data is added or actually changed.  SQL Server does not keep statistics to show how much MAX or TEXT data is currently in-row, and how much is stored in LOB pages.  This is an annoying limitation, and one which I hope will be addressed in a future version of the product. So why should we worry about this?  Excessive memory grants reduce concurrency and may result in queries waiting on the RESOURCE_SEMAPHORE wait type while they wait for memory they do not need.  245MB is an awful lot of memory, especially on 32-bit versions where memory grants cannot use AWE-mapped memory.  Even on a 64-bit server with plenty of memory, do you really want a single query to consume 0.25GB of memory unnecessarily?  That’s 32,000 8KB pages that might be put to much better use. The Solution The answer is not to use the TEXT data type for the padding column.  That solution happens to have better performance characteristics for this specific query, but it still results in a spilled sort, and it is hard to recommend the use of a data type which is scheduled for removal.  I hope it is clear to you that the fundamental problem here is that SQL Server sorts the whole set arriving at a Sort operator.  Clearly, it is not efficient to sort the whole table in memory just to return 150 rows in a random order. The TEXT example was more efficient because it dramatically reduced the size of the set that needed to be sorted.  We can do the same thing by selecting 150 unique keys from the table at random (sorting by NEWID() for example) and only then retrieving the large padding column values for just the 150 rows we need.  The following script implements that idea for all four tables: SET STATISTICS IO ON ; WITH TestTable AS ( SELECT * FROM dbo.TestCHAR ), TopKeys AS ( SELECT TOP (150) id FROM TestTable ORDER BY NEWID() ) SELECT T1.id, T1.padding FROM TestTable AS T1 WHERE T1.id = ANY (SELECT id FROM TopKeys) OPTION (MAXDOP 1) ; WITH TestTable AS ( SELECT * FROM dbo.TestMAX ), TopKeys AS ( SELECT TOP (150) id FROM TestTable ORDER BY NEWID() ) SELECT T1.id, T1.padding FROM TestTable AS T1 WHERE T1.id IN (SELECT id FROM TopKeys) OPTION (MAXDOP 1) ; WITH TestTable AS ( SELECT * FROM dbo.TestTEXT ), TopKeys AS ( SELECT TOP (150) id FROM TestTable ORDER BY NEWID() ) SELECT T1.id, T1.padding FROM TestTable AS T1 WHERE T1.id IN (SELECT id FROM TopKeys) OPTION (MAXDOP 1) ; WITH TestTable AS ( SELECT * FROM dbo.TestMAXOOR ), TopKeys AS ( SELECT TOP (150) id FROM TestTable ORDER BY NEWID() ) SELECT T1.id, T1.padding FROM TestTable AS T1 WHERE T1.id IN (SELECT id FROM TopKeys) OPTION (MAXDOP 1) ; SET STATISTICS IO OFF ; All four queries now return results in much less than a second, with memory grants between 6 and 12MB, and without spilling to tempdb.  The small remaining inefficiency is in reading the id column values from the clustered primary key index.  As a clustered index, it contains all the in-row data at its leaf.  The CHAR and VARCHAR(MAX) tables store the padding column in-row, so id values are separated by a 3999-character column, plus row overhead.  The TEXT and MAXOOR tables store the padding values off-row, so id values in the clustered index leaf are separated by the much-smaller off-row pointer structure.  This difference is reflected in the number of logical page reads performed by the four queries: Table 'TestCHAR' logical reads 25511 lob logical reads 000 Table 'TestMAX'. logical reads 25511 lob logical reads 000 Table 'TestTEXT' logical reads 00412 lob logical reads 597 Table 'TestMAXOOR' logical reads 00413 lob logical reads 446 We can increase the density of the id values by creating a separate nonclustered index on the id column only.  This is the same key as the clustered index, of course, but the nonclustered index will not include the rest of the in-row column data. CREATE UNIQUE NONCLUSTERED INDEX uq1 ON dbo.TestCHAR (id); CREATE UNIQUE NONCLUSTERED INDEX uq1 ON dbo.TestMAX (id); CREATE UNIQUE NONCLUSTERED INDEX uq1 ON dbo.TestTEXT (id); CREATE UNIQUE NONCLUSTERED INDEX uq1 ON dbo.TestMAXOOR (id); The four queries can now use the very dense nonclustered index to quickly scan the id values, sort them by NEWID(), select the 150 ids we want, and then look up the padding data.  The logical reads with the new indexes in place are: Table 'TestCHAR' logical reads 835 lob logical reads 0 Table 'TestMAX' logical reads 835 lob logical reads 0 Table 'TestTEXT' logical reads 686 lob logical reads 597 Table 'TestMAXOOR' logical reads 686 lob logical reads 448 With the new index, all four queries use the same query plan (click to enlarge): Performance Summary: 0.3 seconds elapsed time 6MB memory grant 0MB tempdb usage 1MB sort set 835 logical reads (CHAR, MAX) 686 logical reads (TEXT, MAXOOR) 597 LOB logical reads (TEXT) 448 LOB logical reads (MAXOOR) No sort warning I’ll leave it as an exercise for the reader to work out why trying to eliminate the Key Lookup by adding the padding column to the new nonclustered indexes would be a daft idea Conclusion This post is not about tuning queries that access columns containing big strings.  It isn’t about the internal differences between TEXT and MAX data types either.  It isn’t even about the cool use of UPDATE .WRITE used in the MAXOOR table load.  No, this post is about something else: Many developers might not have tuned our starting example query at all – 5 seconds isn’t that bad, and the original query plan looks reasonable at first glance.  Perhaps the NEWID() function would have been blamed for ‘just being slow’ – who knows.  5 seconds isn’t awful – unless your users expect sub-second responses – but using 250MB of memory and writing 200MB to tempdb certainly is!  If ten sessions ran that query at the same time in production that’s 2.5GB of memory usage and 2GB hitting tempdb.  Of course, not all queries can be rewritten to avoid large memory grants and sort spills using the key-lookup technique in this post, but that’s not the point either. The point of this post is that a basic understanding of execution plans is not enough.  Tuning for logical reads and adding covering indexes is not enough.  If you want to produce high-quality, scalable TSQL that won’t get you paged as soon as it hits production, you need a deep understanding of execution plans, and as much accurate, deep knowledge about SQL Server as you can lay your hands on.  The advanced database developer has a wide range of tools to use in writing queries that perform well in a range of circumstances. By the way, the examples in this post were written for SQL Server 2008.  They will run on 2005 and demonstrate the same principles, but you won’t get the same figures I did because 2005 had a rather nasty bug in the Top N Sort operator.  Fair warning: if you do decide to run the scripts on a 2005 instance (particularly the parallel query) do it before you head out for lunch… This post is dedicated to the people of Christchurch, New Zealand. © 2011 Paul White email: @[email protected] twitter: @SQL_Kiwi

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  • Samba server NETBIOS name not resolving, WINS support not working

    - by Eric
    When I try to connect to my CentOS 6.2 x86_64 server's samba shares using address \\REPO (NETBIOS name of REPO), it times out and shows an error; if I do so directly via IP, it works fine. Furthermore, my server does not work correctly as a WINS server despite my samba settings being correct for it (see below for details). If I stop the iptables service, things work properly. I'm using this page as a reference for which ports to use: http://www.samba.org/samba/docs/server_security.html Specifically: UDP/137 - used by nmbd UDP/138 - used by nmbd TCP/139 - used by smbd TCP/445 - used by smbd I really really really want to keep the secure iptables design I have below but just fix this particular problem. SMB.CONF [global] netbios name = REPO workgroup = AWESOME security = user encrypt passwords = yes # Use the native linux password database #passdb backend = tdbsam # Be a WINS server wins support = yes # Make this server a master browser local master = yes preferred master = yes os level = 65 # Disable print support load printers = no printing = bsd printcap name = /dev/null disable spoolss = yes # Restrict who can access the shares hosts allow = 127.0.0. 10.1.1. [public] path = /mnt/repo/public create mode = 0640 directory mode = 0750 writable = yes valid users = mangs repoman IPTABLES CONFIGURE SCRIPT # Remove all existing rules iptables -F # Set default chain policies iptables -P INPUT DROP iptables -P FORWARD DROP iptables -P OUTPUT DROP # Allow incoming SSH iptables -A INPUT -i eth0 -p tcp --dport 22222 -m state --state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -o eth0 -p tcp --sport 22222 -m state --state ESTABLISHED -j ACCEPT # Allow incoming HTTP #iptables -A INPUT -i eth0 -p tcp --dport 80 -m state --state NEW,ESTABLISHED -j ACCEPT #iptables -A OUTPUT -o eth0 -p tcp --sport 80 -m state --state ESTABLISHED -j ACCEPT # Allow incoming Samba iptables -A INPUT -i eth0 -p udp --dport 137 -m state --state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -o eth0 -p udp --sport 137 -m state --state ESTABLISHED -j ACCEPT iptables -A INPUT -i eth0 -p udp --dport 138 -m state --state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -o eth0 -p udp --sport 138 -m state --state ESTABLISHED -j ACCEPT iptables -A INPUT -i eth0 -p tcp --dport 139 -m state --state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -o eth0 -p tcp --sport 139 -m state --state ESTABLISHED -j ACCEPT iptables -A INPUT -i eth0 -p tcp --dport 445 -m state --state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -o eth0 -p tcp --sport 445 -m state --state ESTABLISHED -j ACCEPT # Make these rules permanent service iptables save service iptables restart**strong text**

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  • Postfix not delivering from external senders and not logging anything

    - by simendsjo
    Some semi-recent upgrades must have broken my postfix+dovecot configuration, but I'm having problems finding out what the cause is. My domain is simendsjo.me with the MX record mail.simendsjo.me. I can send mail to both local and external recipients, and it delivers mail from internal mailboxes. The problem is that mail from external senders isn't delivered, and nothing is logged at all. The external sender also doesn't receive any errors. I have no idea where to ever start looking as nothing is logged at all when external mail is sent to my server. So the first issue would be: How can I turn on some debug messages for postfix? I've tried: debug_peer_level = 2 debug_peer_list = simendsjo.me .. And _level = 999 and _list = gmail.com where I'm trying to send emails from. but nothing is logged. When sending mails from a local mailbox (but from an outside computer, not localhost), a lot is logged. I don't have any rules in iptables either. Any ideas how I can get some debug messages for postfix?

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  • why do we need advanced knowledge of mathematics & physics for programming?

    - by Sumeet
    Guys, I have been very good in mathematics and physics in my schools and colleges. Right now I am a programmer. Even in the colleges I have to engrossed my self into computers and programming things all the time. As I used to like it very much. But I have always felt the lack of advanced mathematics and physics in all the work I have done (Programs). Programming never asked me any advanced mathematics and physics knowledge in what I was very good. It always ask u some optimized loops, and different programming technologies which has never been covered in advanced mathematics and physics. Even at the time of selection in big College , such a kind of advanced knowledge is required. Time by time I got out of touch of all that facts and concepts (advanced mathematics and physics). And now after, 5 years in job I found it hard to resolve Differentiations and integrations from Trigonometry. Which sometimes make me feel like I have wasted time in those concepts because they are never used. (At that time I knew that I am going to be a programmer) If one need to be a programmer why do all this advanced knowledge is required. One can go with elementry knowledge a bit more. You never got to think like scientists and R&D person in your Schols and colleges for being a programmer? Just think and let me know your thoughts. I must be wrong somewhere in what I think , but not able to figure that out..? Regards Sumeet

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  • Why is Automator crashing on launch?

    - by zbrimhall
    I've run into an odd problem where Automtor.app on Snow Leopard crashes on launch. At some point in the past, I put a copy of iPhoto.app into my public directory to copy over to another machine. Now, Automator.app won't run unless my public directory has a copy of iPhoto.app in it. If I remove it, Automator.app crashes on launch. Here's what happens: Launch Automator.app After the Automator menu bar appears, but before any windows appear, I get the dreaded beach ball for a few seconds Automator crashes Here's the output from Console.app: 12/26/09 2:11:24 PM Automator[11736] The action “Add Movie to iDVD Menu” could not be loaded because the application “iDVD” was not found. 12/26/09 2:11:24 PM Automator[11736] The action “Get iDVD Slideshow Images” could not be loaded because the application “iDVD” was not found. 12/26/09 2:11:24 PM Automator[11736] The action “Initiate Remote Broadcast” could not be loaded because the application “QuickTime Broadcaster” was not found. 12/26/09 2:11:24 PM Automator[11736] The action “New iDVD Menu” could not be loaded because the application “iDVD” was not found. 12/26/09 2:11:24 PM Automator[11736] The action “New iDVD Movie Sequence” could not be loaded because the application “iDVD” was not found. 12/26/09 2:11:24 PM Automator[11736] The action “New iDVD Slideshow” could not be loaded because the application “iDVD” was not found. 12/26/09 2:11:24 PM Automator[11736] The action “New QuickTime Slideshow” could not be loaded because the application “QuickTime Player” was not found. 12/26/09 2:11:24 PM Automator[11736] The action “Set iDVD Background Image” could not be loaded because the application “iDVD” was not found. 12/26/09 2:11:24 PM Automator[11736] The action “Set iDVD Button Face” could not be loaded because the application “iDVD” was not found. 12/26/09 2:11:24 PM Automator[11736] The action “Set Movie Annotations” could not be loaded because the application “QuickTime Player” was not found. 12/26/09 2:11:24 PM Automator[11736] The action “Set Movie Playback Properties” could not be loaded because the application “QuickTime Player” was not found. 12/26/09 2:11:24 PM Automator[11736] The action “Set Movie URL” could not be loaded because the application “QuickTime Player” was not found. 12/26/09 2:11:24 PM Automator[11736] The action “Show Main iDVD Menu” could not be loaded because the application “iDVD” was not found. 12/26/09 2:11:25 PM Automator[11736] Can not ID UTI for path The value %@ is invalid.: The file “The value %@ is invalid.” couldn’t be opened because there is no such file. 12/26/09 2:11:25 PM Automator[11736] Can not ID UTI for path /Users/brimhall/Public/iPhoto.app: The file “iPhoto.app” couldn’t be opened because there is no such file. 12/26/09 2:11:25 PM Automator[11736] Can not ID UTI for path The value %@ is invalid.: The file “The value %@ is invalid.” couldn’t be opened because there is no such file. 12/26/09 2:11:26 PM Automator[11736] -[NSAttributeDictionary length]: unrecognized selector sent to instance 0x49c770 12/26/09 2:11:26 PM Automator[11736] -[NSAttributeDictionary length]: unrecognized selector sent to instance 0x49c770 12/26/09 2:11:38 PM com.apple.launchd.peruser.501[203] ([0x0-0x2ad2ad].com.apple.Automator[11736]) Job appears to have crashed: Segmentation fault I've tried deleting my Automator.app Preferences file and Application Support directory to get it to look for iPhoto.app in the system-wide Applications directory, but to no avail. Any suggestions on how I can get things working as normal?

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  • Why is Automator crashing on launch?

    - by zbrimhall
    I've run into an odd problem where Automtor.app on Snow Leopard crashes on launch. At some point in the past, I put a copy of iPhoto.app into my public directory to copy over to another machine. Now, Automator.app won't run unless my public directory has a copy of iPhoto.app in it. If I remove it, Automator.app crashes on launch. Here's what happens: Launch Automator.app After the Automator menu bar appears, but before any windows appear, I get the dreaded beach ball for a few seconds Automator crashes Here's the output from Console.app: 12/26/09 2:11:24 PM Automator[11736] The action “Add Movie to iDVD Menu” could not be loaded because the application “iDVD” was not found. 12/26/09 2:11:24 PM Automator[11736] The action “Get iDVD Slideshow Images” could not be loaded because the application “iDVD” was not found. 12/26/09 2:11:24 PM Automator[11736] The action “Initiate Remote Broadcast” could not be loaded because the application “QuickTime Broadcaster” was not found. 12/26/09 2:11:24 PM Automator[11736] The action “New iDVD Menu” could not be loaded because the application “iDVD” was not found. 12/26/09 2:11:24 PM Automator[11736] The action “New iDVD Movie Sequence” could not be loaded because the application “iDVD” was not found. 12/26/09 2:11:24 PM Automator[11736] The action “New iDVD Slideshow” could not be loaded because the application “iDVD” was not found. 12/26/09 2:11:24 PM Automator[11736] The action “New QuickTime Slideshow” could not be loaded because the application “QuickTime Player” was not found. 12/26/09 2:11:24 PM Automator[11736] The action “Set iDVD Background Image” could not be loaded because the application “iDVD” was not found. 12/26/09 2:11:24 PM Automator[11736] The action “Set iDVD Button Face” could not be loaded because the application “iDVD” was not found. 12/26/09 2:11:24 PM Automator[11736] The action “Set Movie Annotations” could not be loaded because the application “QuickTime Player” was not found. 12/26/09 2:11:24 PM Automator[11736] The action “Set Movie Playback Properties” could not be loaded because the application “QuickTime Player” was not found. 12/26/09 2:11:24 PM Automator[11736] The action “Set Movie URL” could not be loaded because the application “QuickTime Player” was not found. 12/26/09 2:11:24 PM Automator[11736] The action “Show Main iDVD Menu” could not be loaded because the application “iDVD” was not found. 12/26/09 2:11:25 PM Automator[11736] Can not ID UTI for path The value %@ is invalid.: The file “The value %@ is invalid.” couldn’t be opened because there is no such file. 12/26/09 2:11:25 PM Automator[11736] Can not ID UTI for path /Users/brimhall/Public/iPhoto.app: The file “iPhoto.app” couldn’t be opened because there is no such file. 12/26/09 2:11:25 PM Automator[11736] Can not ID UTI for path The value %@ is invalid.: The file “The value %@ is invalid.” couldn’t be opened because there is no such file. 12/26/09 2:11:26 PM Automator[11736] -[NSAttributeDictionary length]: unrecognized selector sent to instance 0x49c770 12/26/09 2:11:26 PM Automator[11736] -[NSAttributeDictionary length]: unrecognized selector sent to instance 0x49c770 12/26/09 2:11:38 PM com.apple.launchd.peruser.501[203] ([0x0-0x2ad2ad].com.apple.Automator[11736]) Job appears to have crashed: Segmentation fault I've tried deleting my Automator.app Preferences file and Application Support directory to get it to look for iPhoto.app in the system-wide Applications directory, but to no avail. Any suggestions on how I can get things working as normal?

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  • Why doesn't the .click() not work in this instance?

    - by Deshiknaves
    Basically what this does is fadeIn pre-existing divs and then loads an image. When the image is loaded it then appends that into one of the pre-existing divs. Then it appends a new div with an id of xButton. Then later it $('#xButton').click() should hide the 3 divs. However it just doesn't work. If I change the click() to either #modalImage or #overlay, it works but just not for the #xButton. I would really like to figure out why its not working and how I should be doing this instead. Thanks. $(function(){ $('#container a').click(function(e){ e.preventDefault(); var id = $(this).attr('href'), img = new Image(); $('#overlay').fadeIn(function(){ $('#modalImage').fadeIn(); }); $(img).load(function(){ $(this).hide(); $('#modalImage').removeClass('loader').append(this); $(this).fadeIn(function(){ var ih = $(this).outerHeight(), iw = $(this).outerWidth(), newH = ($(window).height()/10)*7, newW = ($(window).width()/10)*7; if (ih >= iw && ih >= newH) { $(this).css('height',newH + 'px'); $(this).css('width', 'auto'); } else if (ih >= iw && newH > ih) { $(this).css('height', ih + 'px'); $(this).css('width', 'auto'); } else if (iw > ih && iw >= newW) { if ((newW / (iw / ih)) > newH) { $(this).css('width', 'auto'); $(this).css('height', newH + 'px'); } else { $(this).css('width', newW + 'px'); $(this).css('height', 'auto'); } } else { $(this).css('width', iw + 'px'); $(this).css('height', 'auto'); } var padW = ($(window).width() - $(this).outerWidth()) / 2, padH = ($(window).height() - $(this).outerHeight()) / 2; console.log (padH + ' ' + padW); $(this).css('top', padH); $(this).css('left', padW); if($('#overlay').is(":visible") == true) { ih = ih + 4; $('<div id="xButton">x</div>').appendTo('#modalImage'); if (padH >= 0) { $('#xButton').css('top', padH - 4).css('right', padW - 65); } else { $('#xButton').css('top', '20px').css('right', padW - 65); } } }); }).attr('src', id); }); $('#xButton').click(function(){ $(this).hide(); $('#overlay').fadeOut(function(){ $('#modalImage img').css('top', '-9999px').remove(); $('#xButton').remove(); $('#modalImage').addClass('loader'); }); }); });

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  • HTG Explains: Why Linux Doesn’t Need Defragmenting

    - by Chris Hoffman
    If you’re a Linux user, you’ve probably heard that you don’t need to defragment your Linux file systems. You’ll also notice that Linux distributions don’t come with disk-defragmenting utilities. But why is that? To understand why Linux file systems don’t need defragmenting in normal use – and Windows ones do – you’ll need to understand why fragmentation occurs and how Linux and Windows file systems work differently from each other. HTG Explains: Why Linux Doesn’t Need Defragmenting How to Convert News Feeds to Ebooks with Calibre How To Customize Your Wallpaper with Google Image Searches, RSS Feeds, and More

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  • Why your Netapp is so slow...

    - by Darius Zanganeh
    Have you ever wondered why your Netapp FAS box is slow and doesn't perform well at large block workloads?  In this blog entry I will give you a little bit of information that will probably help you understand why it’s so slow, why you shouldn't use it for applications that read and write in large blocks like 64k, 128k, 256k ++ etc..  Of course since I work for Oracle at this time, I will show you why the ZS3 storage boxes are excellent choices for these types of workloads. Netapp’s Fundamental Problem The fundamental problem you have running these workloads on Netapp is the backend block size of their WAFL file system.  Every application block on a Netapp FAS ends up in a 4k chunk on a disk. Reference:  Netapp TR-3001 Whitepaper Netapp has proven this lacking large block performance fact in at least two different ways. They have NEVER posted an SPC-2 Benchmark yet they have posted SPC-1 and SPECSFS, both recently. In 2011 they purchased Engenio to try and fill this GAP in their portfolio. Block Size Matters So why does block size matter anyways?  Many applications use large block chunks of data especially in the Big Data movement.  Some examples are SAS Business Analytics, Microsoft SQL, Hadoop HDFS is even 64MB! Now let me boil this down for you.  If an application such MS SQL is writing data in a 64k chunk then before Netapp actually writes it on disk it will have to split it into 16 different 4k writes and 16 different disk IOPS.  When the application later goes to read that 64k chunk the Netapp will have to again do 16 different disk IOPS.  In comparison the ZS3 Storage Appliance can write in variable block sizes ranging from 512b to 1MB.  So if you put the same MSSQL database on a ZS3 you can set the specific LUNs for this database to 64k and then when you do an application read/write it requires only a single disk IO.  That is 16x faster!  But, back to the problem with your Netapp, you will VERY quickly run out of disk IO and hit a wall.  Now all arrays will have some fancy pre fetch algorithm and some nice cache and maybe even flash based cache such as a PAM card in your Netapp but with large block workloads you will usually blow through the cache and still need significant disk IO.  Also because these datasets are usually very large and usually not dedupable they are usually not good candidates for an all flash system.  You can do some simple math in excel and very quickly you will see why it matters.  Here are a couple of READ examples using SAS and MSSQL.  Assume these are the READ IOPS the application needs even after all the fancy cache and algorithms.   Here is an example with 128k blocks.  Notice the numbers of drives on the Netapp! Here is an example with 64k blocks You can easily see that the Oracle ZS3 can do dramatically more work with dramatically less drives.  This doesn't even take into account that the ONTAP system will likely run out of CPU way before you get to these drive numbers so you be buying many more controllers.  So with all that said, lets look at the ZS3 and why you should consider it for any workload your running on Netapp today.  ZS3 World Record Price/Performance in the SPC-2 benchmark ZS3-2 is #1 in Price Performance $12.08ZS3-2 is #3 in Overall Performance 16,212 MBPS Note: The number one overall spot in the world is held by an AFA 33,477 MBPS but at a Price Performance of $29.79.  A customer could purchase 2 x ZS3-2 systems in the benchmark with relatively the same performance and walk away with $600,000 in their pocket.

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  • grep -v -A not working properly (actually not working at all)

    - by Lo'oris
    I have to filter lines like the following: [javac] /Users/looris/Sviluppo/android/projects/toutry/src/net/looris/toutry/Stuff.java:23: warning: unmappable character for encoding ascii [javac] return (poked=false); // NOTA: è un'assegnazione, non un controllo! [javac] ^ I've tried |grep -v -A2 "unmappable character for encoding ascii" but it just does nothing. If I just do |grep -v "unmappable character for encoding ascii" it does filter that line, but I need to filter the following two lines too. (using "grep (GNU grep) 2.5.1" under OSX 10.5)

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  • Windows 7 Not Starting and System Repair Not Loading

    - by Mark
    I have a Dell Inspiron 1545 running Windows 7 When turning on my PC I keep receiving a black screen with the option to use System Repair or Start Normally. Both options lead me to the System Repair background except no matter how long I wait the system restore options never show up. Choosing F8 and running all of the options including safe mode encounters the same result above. I tried to to use 2 system recovery disks 32x and 64x I downloaded and both lead to similiar results. When I choose System Repair running from the disk the System Repair Question asking to select a language pops ups but after this no matter how long I wait no other options appear. Next after restarting and selecting F8 (after hitting f12 and running from CD) I choose 'Run From Safe Mode with Command Prompt' I am able to run all of the options from System Restore with differing results: Startup Repair: Choosing this ends up in system repair indefinitely (left running 12 hrs) System Restore: Does Nothing. PC thinks for a second and then stops. When selecting ShutDown I see an error message stating there are no restore points. System Image Recovery: Service Cannot be started in Safe Mode Windows Memory Diagnostic: Runs test but then leads to system repair background which never loads system repair Command Prompt: chkdsk /r -Cannot Lock Current Drive...write protected. chkdsk /f -Cannot Lock Current Drive...write protected. bootcfg - Cannot open Boot.Ini file bootcfg - Ran all 3 (rebuildBcd, FixMbr and Fixboot) but PC still goes to System Repair background with no repair options popping up upon restart (without recovery CD). I'm on the verge of purchasing a boot utility disk for $50 unless there is anything else short of "take it to a computer shop" that somebody can suggest I try.

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  • Why fork a library for your own application?

    - by Mr. Shickadance
    Why should a programmer ever fork a library for inclusion in a widely used application? I ask this question because I was reading an article about why Chromium isn't packaged for many Linux distros like Fedora. Apparently its largely due to the fact that Google has forked a number of libraries, modified them, and included them in Chromium. This has driven up the complexity of packaging releases. There are a number of reasons why this can be a bad thing, but how strong a case can you actually make for doing so in a large widely used application such as Chromium? The original article: http://ostatic.com/blog/making-projects-easier-to-package-why-chromium-isnt-in-fedora Isn't it usually worth the effort to make slight modifications to your own program in order to use a popular and well developed library?

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  • Windows scheduler - Tasks not running when user not logged in

    - by Glinkot
    I have Windows Server 2003, with schedules setup via Remote Desktop under one account. That account appears in the 'creator' column too. I have 'Run only if logged on' unticked. When I have logged in under that account and then 'disconnected' leaving the the session alive, the schedule runs. But every time the server is rebooted, the task again fails to run until I again log in and disconnect. Any KB fixes I've missed or issues I've overlooked? Normally I only discover the issue when a user tells me the schedule has stopped running so it's a real reliability issue. I'd also be happy with an answer suggesting an alternative scheduler with higher reliability. Thanks

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  • mailsend not sending to (or qmail not receiving from) the same machine

    - by roman
    A web applications sends two emails: to the user of the webapp to the administrator the administrators mailbox (qmail) is on the same machine as the web application (php, apache, /usr/sbin/sendmail). email 1 works, email 2 sometimes doesn't work. I don't see any pattern in the mails that don't work. Also because I don't exactly know WHICH emails failed (since the email itself would be the only notification). email 2 looks like this: from: <[email protected]> #changes for each user to: <[email protected]> What could be the problem? Are rejected emails stored somewhere? (if they are rejected.. how do I check this?)

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  • DPMS does not work: the monitor is not switched off

    - by bortzmeyer
    I have a monitor which was properly switched off by my Debian PC when unused. I attached it to another machine and, this times, it is never switched off. In /etc/X11/xorg.conf, I have: Section "Monitor" Identifier "Generic Monitor" Option "DPMS" It is recognized when X11 starts: (II) Loading extension DPMS ... (II) VESA(0): DPMS capabilities: StandBy Suspend Off; RGB/Color Display ... (**) Option "dpms" (**) VESA(0): DPMS enabled The operating system is Debian stable "lenny". The graphics card is: 00:02.0 VGA compatible controller: Intel Corporation 82G33/G31 Express Integrate d Graphics Controller (rev 02) (prog-if 00 [VGA controller]) Subsystem: Hewlett-Packard Company Device 2a6f Flags: bus master, fast devsel, latency 0, IRQ 5 Memory at fe900000 (32-bit, non-prefetchable) [size=512K] I/O ports at b080 [size=8] Memory at d0000000 (32-bit, prefetchable) [size=256M] Memory at fe800000 (32-bit, non-prefetchable) [size=1M] Capabilities: [90] Message Signalled Interrupts: Mask- 64bit- Queue=0/0 Enable-Capabilities: [d0] Power Management version 2 X11 is: X.Org X Server 1.4.2 Release Date: 11 June 2008 X Protocol Version 11, Revision 0 Build Operating System: Linux Debian (xorg-server 2:1.4.2-10.lenny2) Current Operating System: Linux ludwigVII 2.6.26-2-686 #1 SMP Sun Jun 21 04:57:3 8 UTC 2009 i686 Build Date: 08 June 2009 09:12:57AM

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  • Cisco ASA site-to-site vpn not initiating phase 1 (not sending udp 500 packets)

    - by Sean Steadman
    I am hoping someone here can help me with my problem. I am trying to setup an IPSEC site-to-site VPN between two cisco ASA 5520's in GNS3 (both using 8.4.2). I have been unsuccesful in getting the tunnel up and it appears neither ASA is sending packets out,in regards to phase 1 and phase 2 (tested by using wireshark and seeing NO udp 500 packets). Doing show ipsec sa and such shows nothing. CALIFORNIA(config)# show ipsec sa There are no ipsec sas FLA-ASA# show ipsec sa There are no ipsec sas I will attach both configurations in two different pastebin files as to keep this post a bit cleaner. Essentially California side has 172.20.1.0/24 and Florida side has 10.10.10.0/24. California ASA config: http://pastebin.com/v0pngYzF Florida ASA config: http://pastebin.com/E2geybta Please let me know if there is any other vital information that could help. I have gotten IPSEC tunnels to work using openSwan (linux) and cisco routers but cannot for the life of me get ASA IPSEC tunnels to work. The ASDM is out of the question I only use cli. Thanks for any useful help!

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  • Mouse works fine but keyboard (not wireless) not responding to anything

    - by Christine Boeke
    I read previous questions like mine and looked to see if keys were depressed and checked to make sure the mouse key was off in the system preferences. The mouse works just fine but the keyboard seems to be dead. I plugged in another keyboard and it responded identically. Is it something in the Desktop itself? Could I need a technician? I have searched for answers on line and had no success. Thanks!

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  • Why are there different programming languages [closed]

    - by Velizar Hristov
    I'm not asking about the usefulness of the languages that do exist already: I already know, and agree, that different languages are better for different purposes. However, why don't they just have a single language that can do it all? Why, when C# was created, they didn't keep everything from C and C++ and just add a few things, so that it can be used as both a low-level and high-level language? I see no harm in adding all kinds of commands to a single language that would allow it to be good for everything, and even eliminate the need for all other languages. Someone from another thread said that if there's a flaw in a certain language, its successor might not have it. However, why don't we just update that language to remove the flaw, and/or add anything that's missing? Arrays are different in Java and C#, but why not have them both, just use different commands for them? And so on...

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  • Why does Facebook convert PHP code to C++?

    - by user72245
    I read that Facebook started out in PHP, and then to gain speed, they now compile PHP as C++ code. If that's the case why don't they: Just program in c++? Surely there must be SOME errors/bugs when hitting a magic compiler button that ports PHP to c++ code , right? If this impressive converter works so nicely, why stick to PHP at all? Why not use something like Ruby or Python? Note -- I picked these two at random, but mostly because nearly everyone says coding in those languages is a "joy". So why not develop in a super great language and then hit the magic c++ compile button?

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  • Why is git-svn useful?

    - by Wes
    I have read these related questions: I'm a Subversion geek, why should I consider or not consider Mercurial or Git or any other DVCS? git for personal (one-man) projects. Overkill? ...and I understand why git is useful. What I don't understand is why tools like git-svn that allow git to integrate with svn are useful. When, for example, a team is working with svn, or any other centralised SCM, why would a member of the team opt to use git-svn? Are there any practical advantages for a developer that has to synchronize with a centralized repository?

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