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• What is the best way to auto-generate INSERT statements for a SQL Server table?

  - by JosephStyons

  We are writing a new application, and while testing, we will need a bunch of dummy data. I've added that data by using MS Access to dump excel files into the relevant tables. Every so often, we want to "refresh" the relevant tables, which means dropping them all, re-creating them, and running a saved MS Access append query. The first part (dropping & re-creating) is an easy sql script, but the last part makes me cringe. I want a single setup script that has a bunch of INSERTs to regenerate the dummy data. I have the data in the tables now. What is the best way to automatically generate a big list of INSERT statements from that dataset? I'm thinking of something like in TOAD (for Oracle) where you can right-click on a grid and click Save As-Insert Statements, and it will just dump a big sql script wherever you want. The only way I can think of doing it is to save the table to an excel sheet and then write an excel formula to create an INSERT for every row, which is surely not the best way. I'm using the 2008 Management Studio to connect to a SQL Server 2005 database.

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• FreeBSD ZFS RAID-Z2 performance issues

  - by Axel Gneiting

  I'm trying to build my own network attached storage based on FreeBSD+ZFS+standard components, but there are strange performance issues. The hardware specs are: AMD Athlon II X2 240e processor ASUS M4A78LT-M LE mainboard 2GiB Kingston ECC DDR3 (two sticks) Intel Pro/1000 CT PCIe network adapter 5x Western Digital Caviar Green 1.5TB I created a RAID-Z2 zpool from all disks. I installed FreeBSD 8.1 on that zpool following the tutorial. The SATA controllers are running in AHCI mode. Output of zpool status: pool: zroot state: ONLINE scrub: none requested config: NAME STATE READ WRITE CKSUM zroot ONLINE 0 0 0 raidz2 ONLINE 0 0 0 gptid/7ef815fc-eab6-11df-8ea4-001b2163266d ONLINE 0 0 0 gptid/80344432-eab6-11df-8ea4-001b2163266d ONLINE 0 0 0 gptid/81741ad9-eab6-11df-8ea4-001b2163266d ONLINE 0 0 0 gptid/824af5cb-eab6-11df-8ea4-001b2163266d ONLINE 0 0 0 gptid/82f98a65-eab6-11df-8ea4-001b2163266d ONLINE 0 0 0 The problem is that write performance on the pool is very very bad (<10 MB/s) and every application that is accessing the disk is unresponsive every few seconds when writing. It seems like writing is fine until the ZFS ark cache is full and then ZFS stalls the entire system I/O till it's finished writing that data. Also I'm getting kmem_malloc to small kernel panics. I've already tried to put vm.kmem_size="1500M" vm.kmem_size_max="1500M" into /boot/loader.conf, but it doesn't help. Does anyone know what's going on here? Am I really not having enough memory for ZFS to handle this RAID-Z2?

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• How to protect my SQL Server database from unauthorized access, modification and distribution?

  - by gtas

  What are the ways of protecting a SQL Server without using third party tools and not lose performance?

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• Best way to encrypt certain fiels in SQL Server 2008?

  - by Josh

  I'm writing a .net web app that will read and write information to a SQL 2008 backend database. Some of this information will be highly confidential in nature so I want to encrypt certain data elements. I dont want to use TDE or any full-database encryption for performance reasons. My main concern is protecting this sensitive data as a last resort against a SQL injection or even a database server compromise. My question is what is the best way to do this to preserve performance? Is it faster to use the SQL2008 encryption functions such as EncryptByKey, or would it be faster to encrypt and decrypt the data in the .NET web app itself using a symmetric key stored in the secure web.config and store the encrypted values in the DB?

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• SQL2008R2 install issues on windows 7 - unable to install setup support files?

  - by Liam

  I am trying to install the above but am getting the following errors when its attempting to install the setup support files, This is the first error that occurs during installation of the setup support files TITLE: Microsoft SQL Server 2008 R2 Setup ------------------------------ The following error has occurred: The installer has encountered an unexpected error. The error code is 2337. Could not close file: Microsoft.SqlServer.GridControl.dll GetLastError: 0. Click 'Retry' to retry the failed action, or click 'Cancel' to cancel this action and continue setup. For help, click: http://go.microsoft.com/fwlink?LinkID=20476&ProdName=Microsoft+SQL+Server&EvtSrc=setup.rll&EvtID=50000&ProdVer=10.50.1600.1&EvtType=0xDF039760%25401201%25401 This is the second error that occurs after clicking continue in the installer after the first error is generated TITLE: Microsoft SQL Server 2008 R2 Setup ------------------------------ The following error has occurred: SQL Server Setup has encountered an error when running a Windows Installer file. Windows Installer error message: The Windows Installer Service could not be accessed. This can occur if the Windows Installer is not correctly installed. Contact your support personnel for assistance. Windows Installer file: C:\Users\watto_uk\Desktop\In-Digital\Software\Microsoft\SQL Server 2008 R2\1033_ENU_LP\x64\setup\sqlsupport_msi\SqlSupport.msi Windows Installer log file: C:\Program Files\Microsoft SQL Server\100\Setup Bootstrap\Log\20110713_205508\SqlSupport_Cpu64_1_ComponentUpdate.log Click 'Retry' to retry the failed action, or click 'Cancel' to cancel this action and continue setup. For help, click: http://go.microsoft.com/fwlink?LinkID=20476&ProdName=Microsoft+SQL+Server&EvtSrc=setup.rll&EvtID=50000&ProdVer=10.50.1600.1&EvtType=0xDC80C325 These errors are generated from an ISO package downloaded from Microsoft. I have also tried using the web platform installer to install the express version instead but the SQL Server Installation fails with that also. The management studio installs fine but not the server. I have checked to make sure that the Windows Installer is started and it is. Cant seem to find an answer for this anywhere as all previous reported issues appear to be related to XP. I did have the express edition installed on the machine previously but uninstalled it to upgrade to the full version, I wish I hadn't now. Can anyone kindly offer any advice or point me in the right direction to stop me going insane with this? Any advice will be appreciated. Update======================= After digging a bit deeper ive located details of the error from the setup log file, i can also upload the log file if required. MSI (s) (E8:28) [23:35:18:705]: Assembly Error:The module '%1' was expected to contain an assembly manifest. MSI (s) (E8:28) [23:35:18:705]: Note: 1: 1935 2: 3: 0x80131018 4: IStream 5: Commit 6: MSI (s) (E8:28) [23:35:18:705]: Note: 1: 2337 2: 0 3: Microsoft.SqlServer.GridControl.dll MSI (s) (E8:28) [23:35:22:869]: Product: Microsoft SQL Server 2008 R2 Setup (English) -- Error 2337. The installer has encountered an unexpected error. The error code is 2337. Could not close file: Microsoft.SqlServer.GridControl.dll GetLastError: 0. MSI (s) (E8:28) [23:35:22:916]: Internal Exception during install operation: 0xc0000005 at 0x000007FEE908A23E. MSI (s) (E8:28) [23:35:22:916]: WER report disabled for silent install. MSI (s) (E8:28) [23:35:22:932]: Internal MSI error. Installer terminated prematurely. Error 2337. The installer has encountered an unexpected error. The error code is 2337. Could not close file: Microsoft.SqlServer.GridControl.dll GetLastError: 0. MSI (s) (E8:28) [23:35:22:932]: MainEngineThread is returning 1603 MSI (s) (E8:58) [23:35:22:932]: RESTART MANAGER: Session closed. Installer stopped prematurely. MSI (c) (0C:14) [23:35:22:947]: Decrementing counter to disable shutdown. If counter >= 0, shutdown will be denied. Counter after decrement: -1 MSI (c) (0C:14) [23:35:22:947]: MainEngineThread is returning 1601 === Verbose logging stopped: 13/07/2011 23:35:22 ===

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• Performance tuning of a Hibernate+Spring+MySQL project operation that stores images uploaded by user

  - by Umar

  Hi I am working on a web project that is Spring+Hibernate+MySQL based. I am stuck at a point where I have to store images uploaded by a user into the database. Although I have written some code that works well for now, but I believe that things will mess up when the project would go live. Here's my domain class that carries the image bytes: @Entity public class Picture implements java.io.Serializable{ long id; byte[] data; ... // getters and setters } And here's my controller that saves the file on submit: public class PictureUploadFormController extends AbstractBaseFormController{ ... protected ModelAndView onSubmit(HttpServletRequest request, HttpServletResponse response, Object command, BindException errors) throws Exception{ MutlipartFile file; // getting MultipartFile from the command object ... // beginning hibernate transaction ... Picture p=new Picture(); p.setData(file.getBytes()); pictureDAO.makePersistent(p); // this method simply calls getSession().saveOrUpdate(p) // committing hiernate transaction ... } ... } Obviously a bad piece of code. Is there anyway I could use InputStream or Blob to save the data, instead of first loading all the bytes from the user into the memory and then pushing them into the database? I did some research on hibernate's support for Blob, and found this in Hibernate In Action book: java.sql.Blob and java.sql.Clob are the most efficient way to handle large objects in Java. Unfortunately, an instance of Blob or Clob is only useable until the JDBC transaction completes. So if your persistent class defines a property of java.sql.Clob or java.sql.Blob (not a good idea anyway), you’ll be restricted in how instances of the class may be used. In particular, you won’t be able to use instances of that class as detached objects. Furthermore, many JDBC drivers don’t feature working support for java.sql.Blob and java.sql.Clob. Therefore, it makes more sense to map large objects using the binary or text mapping type, assuming retrieval of the entire large object into memory isn’t a performance killer. Note you can find up-to-date design patterns and tips for large object usage on the Hibernate website, with tricks for particular platforms. Now apparently the Blob cannot be used, as it is not a good idea anyway, what else could be used to improve the performance? I couldn't find any up-to-date design pattern or any useful information on Hibernate website. So any help/recommendations from stackoverflowers will be much appreciated. Thanks

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• How can I access mainframe data with .Net applications and SQL Queries?

  - by orandov

  We have a large amount of data stored on an IBM mainframe using VSAM files. A lot of this data is dropped on the network every night in the form of text files to be processed and dumped into FoxPro and SQL Server databases. There are also many text files produced nightly by custom applications that get uploaded to the mainframe to keep everything in sync. Keeping the everything in sync is very tricky, to say the least. We are not getting rid of the mainframe any time soon and we would like to replace all the nightly batch processing with real time access to the mainframe data. We would like to be able to: Read data directly from the mainframe and produce reports based on it. Possibly using SQL queries. Read and Write data from custom .Net applications. We are not looking for a new platform to interface with the mainframe like Information Builders offers. We don't want to build application modules or reports with new "Business Intelligence" tools. We already know how to generate reports and write custom applications using SQL,.Net, Visual Studio, etc. All we are looking for is some sort of adapter to connect to our mainframe data. Any ideas are appreciated.

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• ORM solutions (JPA; Hibernate) vs. JDBC

  - by Grasper

  I need to be able to insert/update objects at a consistent rate of at least 8000 objects every 5 seconds in an in-memory HSQL database. I have done some comparison performance testing between Spring/Hibernate/JPA and pure JDBC. I have found a significant difference in performance using HSQL.. With Spring/Hib/JPA, I can insert 3000-4000 of my 1.5 KB objects (with a One-Many and a Many-Many relationship) in 5 seconds, while with direct JDBC calls I can insert 10,000-12,000 of those same objects. I cannot figure out why there is such a huge discrepancy. I have tweaked the Spring/Hib/JPA settings a lot trying to get close in performance without luck. I want to use Spring/Hib/JPA for future purposes, expandability, and because the foreign key relationships (one-many and many-many) are difficult to maintain by hand; but the performance requirements seem to point towards using pure JDBC. Any ideas of why there would be such a huge discrepancy?

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• Need help trying to diagnose Symmetrix SAN performance issues

  - by arcain

  I am helping to benchmark hardware for a new SQL Server instance, and the volume presented to the OS for the data files is carved from a set of spindles on a Symmetrix SAN. The server has yet to have SQL Server installed, so the only activity on the box is our benchmarking. Now, our storage engineers say that this volume and it's resources are dedicated to our new server (I don't have access to see the actual SAN config) however the performance benchmarks are troubling. For example, the numbers look good until suddenly, and randomly, we see in our IO benchmarking tool wait times of 100 seconds, and disk queue lengths of 255 in perfmon. This SAN has an 8 GB cache, plus there are other applications besides ours that use the SAN. I'm wondering if (even though the spindles for our volumes should be dedicated to us) the cache may be getting hammered during the performance testing, or perhaps the spindles our volumes are on aren't really dedicated to us. We're not getting much traction from our storage engineers in helping us track down the problem, so if anybody has experience with diagnosing a problem like this and would like to share insights and troubleshooting methodologies, I'd appreciate it.

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• python threading and performace?

  - by kumar

  I had to do heavy I/o bound operation, i.e Parsing large files and converting from one format to other format. Initially I used to do it serially, i.e parsing one after another..! Performance was very poor ( it used take 90+ seconds). So I decided to use threading to improve the performance. I created one thread for each file. ( 4 threads) for file in file_list: t=threading.Thread(target = self.convertfile,args = file) t.start() ts.append(t) for t in ts: t.join() But for my astonishment, there is no performance improvement whatsoever. Now also it takes around 90+ seconds to complete the task. As this is I/o bound operation , I had expected to improve the performance. What am I doing wrong?

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• How to upload files and store them in a server local path when MS SQL SERVER allows remote connectio

  - by user193655

  I am developing a win32 windows application with Delphi and MS SQL Server. it works fine in LAN but I am trying to add the support for SQL Server remote connections (= working with a DB that can be accessed with an external IP, as described in this article: http://support.microsoft.com/default.aspx?scid=kb;EN-US;914277). Basically I have a Table in DB where I keep the DocumentID, the document description and the Document path (like \FILESERVER\MyApplicationDocuments\45.zip). Of course \FILESERVER is a local (LAN) path for the server but not for the client (as I am now trying to add the support for remote connections). So I need a way to access \FILESERVER even if of course I cannot see it in LAN. I found the following T-SQL code snippet that is perfect for the "download trick": SELECT BulkColumn as MyFile FROM OPENROWSET(BULK '\FILESERVER\MyApplicationDocuments\45.zip' , SINGLE_BLOB) AS X With the code above I can download a file on the client. But how to upload it? I need an "Uppload trick" to be able to insert new files, but also to delete or replace existing files. Can anyone suggest? If a trick is not available could you suggest an alternative? Like an extended stored procedure or calling some .net assembly from the server.

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• What's a better choice for SQL-backed number crunching - Ruby 1.9, Python 2, Python 3, or PHP 5.3?

  - by Ivan

  Crterias of 'better': fast im math and simple (little of fields, many records) db transactions, convenient to develop/read/extend, flexible, connectible. The task is to use a common web development scripting language to process and calculate long time series and multidimensional surfaces (mostly selectint/inserting sets of floats and dong maths with rhem). The choice is Ruby 1.9, Python 2, Python 3, PHP 5.3, Perl 5.12, JavaScript (node.js). All the data is to be stored in a relational database (due to its heavily multidimensional nature), all the communication with outer world is to be done by means of web services.

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• How does TopCoder evaluates code?

  - by Carlos

  If you are familiar with TopCoder you know that your source-code gets a final "grade/points" this depends on time, how many compiles, etc, one of the highest weighted being performance. But how can they test that, is there some sort of simple code (java or c++) to do it that you could share for me to evaluate and hopefully write my own to test the programs I write for University? This is sort of a follow up question to this one where I ask if shorter code results in best performance. P.S: Im interested in both of how topcoders knows performance and writing code to test performance.

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• How do I connect to SQL Server with VB?

  - by Wayne Werner

  Hi, I'm trying to connect to a SQL server from VB. The SQL server is across the network uses my windows login for authentication. I can access the server using the following python code: import odbc conn = odbc.odbc('SignInspection') c = conn.cursor() c.execute("SELECT * FROM list_domain") c.fetchone() This code works fine, returning the first result of the SELECT. However, I've been trying to use the SqlClient.SqlConnection in VB, and it fails to connect. I've tried several different connection strings but this is the current code: Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim conn As New SqlClient.SqlConnection conn.ConnectionString = "data source=signinspection;initial catalog=signinspection;integrated security=SSPI" Try conn.Open() MessageBox.Show("Sweet Success") 'Insert some code here, woo Catch ex As Exception MessageBox.Show("Failed to connect to data source.") MessageBox.Show(ex.ToString()) Finally conn.Close() End Try End Sub It fails miserably, and it gives me an error that says "A network-related or instance-specific error occurred... (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server) I'm fairly certain it's my connection string, but nothing I've found has given me any solid examples (server=mySQLServer is not a solid example) of what I need to use. Thanks! -Wayne

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• Can I force the auto-generated Linq-to-SQL classes to use an OUTER JOIN?

  - by Gary McGill

  Let's say I have an Order table which has a FirstSalesPersonId field and a SecondSalesPersonId field. Both of these are foreign keys that reference the SalesPerson table. For any given order, either one or two salespersons may be credited with the order. In other words, FirstSalesPersonId can never be NULL, but SecondSalesPersonId can be NULL. When I drop my Order and SalesPerson tables onto the "Linq to SQL Classes" design surface, the class builder spots the two FK relationships from the Order table to the SalesPerson table, and so the generated Order class has a SalesPerson field and a SalesPerson1 field (which I can rename to SalesPerson1 and SalesPerson2 to avoid confusion). Because I always want to have the salesperson data available whenever I process an order, I am using DataLoadOptions.LoadWith to specify that the two salesperson fields are populated when the order instance is populated, as follows: dataLoadOptions.LoadWith<Order>(o => o.SalesPerson1); dataLoadOptions.LoadWith<Order>(o => o.SalesPerson2); The problem I'm having is that Linq to SQL is using something like the following SQL to load an order: SELECT ... FROM Order O INNER JOIN SalesPerson SP1 ON SP1.salesPersonId = O.firstSalesPersonId INNER JOIN SalesPerson SP2 ON SP2.salesPersonId = O.secondSalesPersonId This would make sense if there were always two salesperson records, but because there is sometimes no second salesperson (secondSalesPersonId is NULL), the INNER JOIN causes the query to return no records in that case. What I effectively want here is to change the second INNER JOIN into a LEFT OUTER JOIN. Is there a way to do that through the UI for the class generator? If not, how else can I achieve this? (Note that because I'm using the generated classes almost exclusively, I'd rather not have something tacked on the side for this one case if I can avoid it).

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• For a set of sql-queries, how do you determine which result-set contains a certain row?

  - by ManBugra

  I have a set of sql - queries: List<String> queries = ... queries[0] = "select id from person where ..."; ... queries[8756] = "select id from person where ..."; Each query selects rows from the same table 'person'. The only difference is the where-clause. Table 'person' looks like this: id | name | ... many other columns How can i determine which queries will contain a certain person in their subset? For example: List<Integer> matchingQueries = magicMethod(queries, [23,45]); The list obtained by 'magicMethod' filters all sql queries present in the list 'queries' (defined above) and returns only those that contain either the person with id 23 OR a person with id 45. Why i need it: I am dealing with an application that contains products and categories where the categories are sql queries that define which products belong to them (queries stored in a table also). Now i have a requirement where an admin has to see all categories an item belongs to immediately after the item was created. Btw, over 8.000 categories defined (so far, more to come). language and db: java && postgreSQL Thanks,

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• What is the correct stage to use for Google Guice in production in an application server?

  - by Yishai

  It seems like a strange question (the obvious answer would Production, duh), but if you read the java docs: /** * We want fast startup times at the expense of runtime performance and some up front error * checking. */ DEVELOPMENT, /** * We want to catch errors as early as possible and take performance hits up front. */ PRODUCTION Assuming a scenario where you have a stateless call to an application server, the initial receiving method (or there abouts) creates the injector new every call. If there all of the module bindings are not needed in a given call, then it would seem to have been better to use the Development stage (which is the default) and not take the performance hit upfront, because you may never take it at all, and here the distinction between "upfront" and "runtime performance" is kind of moot, as it is one call. Of course the downside of this would appear to be that you would lose the error checking, causing potential code paths to cause a problem by surprise. So the question boils down to are the assumptions in the above correct? Will you save performance on a large set of modules when the given lifetime of an injector is one call?

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• Is there a reason why SSIS significantly slows down after a few minutes?

  - by Mark

  I'm running a fairly substantial SSIS package against SQL 2008 - and I'm getting the same results both in my dev environment (Win7-x64 + SQL-x64-Developer) and the production environment (Server 2008 x64 + SQL Std x64). The symptom is that initial data loading screams at between 50K - 500K records per second, but after a few minutes the speed drops off dramatically and eventually crawls embarrasingly slowly. The database is in Simple recovery model, the target tables are empty, and all of the prerequisites for minimally logged bulk inserts are being met. The data flow is a simple load from a RAW input file to a schema-matched table (i.e. no complex transforms of data, no sorting, no lookups, no SCDs, etc.) The problem has the following qualities and resiliences: Problem persists no matter what the target table is. RAM usage is lowish (45%) - there's plenty of spare RAM available for SSIS buffers or SQL Server to use. Perfmon shows buffers are not spooling, disk response times are normal, disk availability is high. CPU usage is low (hovers around 25% shared between sqlserver.exe and DtsDebugHost.exe) Disk activity primarily on TempDB.mdf, but I/O is very low (< 600 Kb/s) OLE DB destination and SQL Server Destination both exhibit this problem. To sum it up, I expect either disk, CPU or RAM to be exhausted before the package slows down, but instead its as if the SSIS package is taking an afternoon nap. SQL server remains responsive to other queries, and I can't find any performance counters or logged events that betray the cause of the problem. I'll gratefully reward any reasonable answers / suggestions.

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• How should I name my SQL query files? Should I use some methodology?

  - by Mehper C. Palavuzlar

  We have an Oracle 10g database (a huge one) in our company, and I provide employees with data upon their requests. My problem is, I save almost every SQL query I wrote, and now my list has grown too much. I want to organize and rename these .sql files so that I can find the one I want easily. At the moment, I'm using some folders named as Sales Dept, Field Team, Planning Dept, Special etc. and under those folders there are .sql files like Delivery_sales_1, Delivery_sales_2, ... Sent_sold_lostsales_endpoints, ... Sales_provinces_period, Returnrates_regions_bymonths, ... Jack_1, Steve_1, Steve_2, ... I try to name the files regarding their content but this makes file names longer and does not completely meet my needs. Sometimes someone comes and demands a special report, and I give the file his name, but this is also not so good. I know duplicates or very similar files are growing in time but I don't have control over them. Can you show me the right direction to rename all these files and folders and organize my queries for easy and better control? TIA.

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• How do I strip multiple (optional) parts of a SQL string using .NET Regular Expressions?

  - by Luc

  I've been working on this for a few hours now and can't find any help on it. Basically, I'm trying to strip a SQL string into various parts (fields, from, where, having, groupBy, orderBy). I refuse to believe that I'm the first person to ever try to do this, so I'd like to ask for some advise from the StackOverflow community. :) To understand what I need, assume the following SQL string: select * from table1 inner join table2 on table1.id = table2.id where field1 = 'sam' having table1.field3 > 0 group by table1.field4 order by table1.field5 I created a regular expression to group the parts accordingly: select\s+(?<fields>.+)\s+from\s+(?<from>.+)\s+where\s+(?<where>.+)\s+having\s+(?<having>.+)\s+group\sby\s+(?<groupby>.+)\s+order\sby\s+(?<orderby>.+) This gives me the following results: fields => * from => table1 inner join table2 on table1.id = table2.id where => field1 = 'sam' having => table1.field3 > 0 groupby => table1.field4 orderby => table1.field5 The problem that I'm faced with is that if any part of the SQL string is missing after the 'from' clause, the regular expression doesn't match. To fix that, I've tried putting each optional part in it's own (...)? group but that doesn't work. It simply put all the optional parts (where, having, groupBy, and orderBy) into the 'from' group. Any ideas?

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• nVidia performance with newer X and newer driver abysmal with Compiz

  - by Nakedible

  I recently upgraded Debian to Xorg 2.9.4 and installed nvidia-glx from experimental, version 260.19.21. This was somewhat of an uphill battle as the dependencies for the experimental nvidia-glx package are still somewhat broken. I got it to work without forcing the installation of any packages and without modifying the packages. However, after the upgrade compiz performance has been abysmal. I am using the desktop wall plugin and switching viewports is really slow - takes a few seconds for each switch. In addition to this, every effect that compiz does, such as zoom animations for icons when launching applications, takes seconds. The viewport switching speed changes relative to the amount of windows on that virtual screen - empty screens switch almost at normal speed, single browser windows work almost decently, but just 4 rxvt terminals slows the switches down to a crawl. My compiz configuration should be pretty basic. Xorg is likewise configured without anything special - the only "custom" configuration is forcing the driver name to be "nvidia". I've fiddled around with the nvidia-settings and compizconfig trying different VSync settings, but none of those helped. My graphics card is: NVIDIA GPU NVS 3100M (GT218) at PCI:1:0:0 (GPU-0). This is laptop GPU that is from the Geforce GTX 200 series. Graphics card performance should naturally be no problem. EDIT: In the end, nothing really worked, and I got really annoyed with the state of compiz and its support in Debian. Many nVidia driver revisions have passed and I am using Gnome 3 now, so I am accepting the best answers to this question even though the issue was not resolved.

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• Linux iptables / conntrack performance issue

  - by tim

  I have a test-setup in the lab with 4 machines: 2 old P4 machines (t1, t2) 1 Xeon 5420 DP 2.5 GHz 8 GB RAM (t3) Intel e1000 1 Xeon 5420 DP 2.5 GHz 8 GB RAM (t4) Intel e1000 to test linux firewall performance since we got bitten by a number of syn-flood attacks in the last months. All machines run Ubuntu 12.04 64bit. t1, t2, t3 are interconnected through an 1GB/s switch, t4 is connected to t3 via an extra interface. So t3 simulates the firewall, t4 is the target, t1,t2 play the attackers generating a packetstorm thorugh (192.168.4.199 is t4): hping3 -I eth1 --rand-source --syn --flood 192.168.4.199 -p 80 t4 drops all incoming packets to avoid confusion with gateways, performance issues of t4 etc. I watch the packet stats in iptraf. I have configured the firewall (t3) as follows: stock 3.2.0-31-generic #50-Ubuntu SMP kernel rhash_entries=33554432 as kernel parameter sysctl as follows: net.ipv4.ip_forward = 1 net.ipv4.route.gc_elasticity = 2 net.ipv4.route.gc_timeout = 1 net.ipv4.route.gc_interval = 5 net.ipv4.route.gc_min_interval_ms = 500 net.ipv4.route.gc_thresh = 2000000 net.ipv4.route.max_size = 20000000 (I have tweaked a lot to keep t3 running when t1+t2 are sending as many packets as possible). The result of this efforts are somewhat odd: t1+t2 manage to send each about 200k packets/s. t4 in the best case sees aroung 200k in total so half of the packets are lost. t3 is nearly unusable on console though packets are flowing through it (high numbers of soft-irqs) the route cache garbage collector is no way near to being predictable and in the default setting overwhelmed by very few packets/s (<50k packets/s) activating stateful iptables rules makes the packet rate arriving on t4 drop to around 100k packets/s, efectively losing more than 75% of the packets And this - here is my main concern - with two old P4 machines sending as many packets as they can - which means nearly everyone on the net should be capable of this. So here goes my question: Did I overlook some importand point in the config or in my test setup? Are there any alternatives for building firewall system especially on smp systems?

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• My program is spending most of its time in objc_msgSend. Does that mean that Objective-C has bad per

  - by Paperflyer

  Hello Stackoverflow. I have written an application that has a number of custom views and generally draws a lot of lines and bitmaps. Since performance is somewhat critical for the application, I spent a good amount of time optimizing draw performance. Now, activity monitor tells me that my application is usually using about 12% CPU and Instrument (the profiler) says that a whopping 10% CPU is spent in objc_msgSend (mostly in drawing related system calls). On the one hand, I am glad about this since it means that my drawing is about as fast as it gets and my optimizations where a huge success. On the other hand, it seems to imply that the only thing that is still using my CPU is the Objective-C overhead for messages (objc_msgSend). Hence, that if I had written the application in, say, Carbon, its performance would be drastically better. Now I am tempted to conclude that Objective-C is a language with bad performance, even though Cocoa seems to be awfully efficient since it can apparently draw faster than Objective-C can send messages. So, is Objective-C really a language with bad performance? What do you think about that?

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• Developing high-performance and scalable zend framework website

  - by Daniel

  We are going to develop an ads website like http://www.gumtree.com/ (it will not be like this one but just to give you an ideea) and we are having some issues regarding performance and scalability. We are planning on using Zend Framework for this project but this is all that I'm sure off at this point. I don't think a classic approch like Zend Framework (PHP) + MySQL + Memcache + jQuery (and I would throw Doctrine 2 in there to) will fix result in a high-performance application. I was thinking on making this a RESTful application (with Zend Framework) + NGINX (or maybe MongoDB) + Memcache (or eAccelerator -- I understand this will create problems with scalability on multiple servers) + jQuery, a CDN for static content, a server for images and a scalable server for the requests and the rest. My questions are: - What do you think about my approch? - What solutions would you recommand in terms of servers approch (MySQL, NGINX, MongoDB or pgsql) for a scalable application expected to have a lot of traffic using PHP?...I would be interested in your approch. Note: I'm a Zend Framework developer and don't have to much experience with the servers part (to determin what would be best solution for my scalable application)

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• Does having a longer string in a SQL Like expression allow hinder or help query executing speed?

  - by Allain Lalonde

  I have a db query that'll cause a full table scan using a like clause and came upon a question I was curious about... Which of the following should run faster in Mysql or would they both run at the same speed? Benchmarking might answer it in my case, but I'd like to know the why of the answer. The column being filtered contains a couple thousand characters if that's important. SELECT * FROM users WHERE data LIKE '%=12345%' or SELECT * FROM users WHERE data LIKE '%proileId=12345%' I can come up for reasons why each of these might out perform the other, but I'm curious to know the logic.

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