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• exploratory SPARQL queries?

  - by significance

  whenever i start using sql i tend to throw a couple of exploratory statements at the database in order to understand what is avaliable, and what form the data takes. eg. show tables describe table select * from table could anyone help me understand the way to complete a similar exploration of an rdf datastore using a SPARQL endpoint? Thanks :)

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• C#/WPF FileSystemWatcher on every extension on every path

  - by BlueMan

  I need FileSystemWatcher, that can observing same specific paths, and specific extensions. But the paths could by dozens, hundreds or maybe thousand (hope not :P), the same with extensions. The paths and ext are added by user. Creating hundreds of FileSystemWatcher it's not good idea, isn't it? So - how to do it? Is it possible to watch/observing every device (HDDs, SD flash, pendrives, etc.)? Will it be efficient? I don't think so... . Every changing Windows log file, scanning file by antyvirus program - it could realy slow down my program with SystemWatcher :(

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• How to use group by for grouping varchar data.

  - by Shantanu Gupta

  I have a table that contains some data given below pk_map_id preferences ImmediateParent Department_Id -------------------- -------------------- -------------------- -------------------- 20 14 5 1 21 15 5 1 22 16 6 1 23 9 4 2 24 4 3 2 25 24 20 2 26 25 20 2 27 23 13 2 I want to group my records on behalf of department then immediate parent then preferences each seperated by ',' i.e. department Immediate Parent preferences 1 5,6 14,15,16 2 4,3,20,13 9,4,24,25,23 and this table also Immediate parent preferences 5 14,15 6 16 4 9 3 4 20 24,25 13 13 In actual scenario all these are my ids which are to be replaced by their string fields. I am using sql server 2k5

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• Creating a Mysql view to SELECT coloumns from different tables

  - by user330429

  I need help in constructing a VIEW on 4 tables. The view should contain coloumns: ER.ID, ER.EMPID, ER.CUSTID, ER.STATUS, ER.DATEREPORTED, ER.REPORT, EB.NAME, CR.CUSTNAME, CR.LOCID, CL.LOCNAME, DI.DEPTNAME ALIASES EMP_REPORT ER , EMP_BIO EB, CUST_RECORD CR, CUST_LOC CL, DEPT_ID DI THE DATA MODELS ARE: describe EMP_REPORT; +--------------+-------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +--------------+-------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | empid | int(11) | NO | | NULL | | | custid | int(11) | NO | | NULL | | | status | varchar(32) | NO | | NULL | | | datereported | bigint(20) | NO | | NULL | | | report | text | YES | | NULL | | +--------------+-------------+------+-----+---------+----------------+ describe EMP_BIO; +--------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +--------+-------------+------+-----+---------+-------+ | empid | int(11) | NO | PRI | NULL | | | name | varchar(56) | NO | | NULL | | | sex | char(1) | NO | | NULL | | | deptid | int(11) | NO | | NULL | | | email | varchar(32) | NO | | NULL | | | mobile | bigint(20) | YES | | NULL | | | gtlk | varchar(32) | YES | | NULL | | | skype | varchar(32) | YES | | NULL | | | cvid | int(11) | YES | | NULL | | +--------+-------------+------+-----+---------+-------+ describe CUST_RECORD; +----------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +----------+--------------+------+-----+---------+----------------+ | custid | int(11) | NO | PRI | NULL | auto_increment | | custname | varchar(32) | NO | | NULL | | | address | varchar(255) | YES | | NULL | | | contactp | varchar(32) | YES | | NULL | | | mobile | bigint(20) | YES | | NULL | | | locid | int(11) | NO | | NULL | | | remarks | text | YES | | NULL | | | date | int(11) | YES | | NULL | | | addedby | int(11) | YES | | NULL | | +----------+--------------+------+-----+---------+----------------+ describe CUST_LOC; +---------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +---------+-------------+------+-----+---------+-------+ | locid | int(11) | NO | PRI | 0 | | | locname | varchar(32) | NO | | NULL | | +---------+-------------+------+-----+---------+-------+ describe DEPT_ID; +----------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +----------+-------------+------+-----+---------+-------+ | deptid | int(11) | NO | | NULL | | | deptname | varchar(32) | YES | | NULL | | +----------+-------------+------+-----+---------+-------+ The table EMP_REPORT contains reports submitted by employees, all the coloumns in it needs to be fetched. The empid in this table should be used to fetch corresponding name in EMP_BIO (employee biodata) table. The custid in EMP_REPORT should be used to fetch corresponding locid in CUST_RECORD(customer record) which is used to fetch locname in CUST_LOC(customer location) table. The empid in EMP_REPORT is used to fetch corresponding deptid in EMP_BIO table which is then used to fetch corresponding deptname from DEPT_ID(department id) table. I tried constructing view using union of different select queries, but dint get proper results. Please help me. Thanks in advance. PS: sorry for my poor english

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• Reasonably faster way to traverse a directory tree in Python?

  - by Sridhar Ratnakumar

  Assuming that the given directory tree is of reasonable size: say an open source project like Twisted or Python, what is the fastest way to traverse and iterate over the absolute path of all files/directories inside that directory? I want to do this from within Python (subprocess is allowed). os.path.walk is slow. So I tried ls -lR and tree -fi. For a project with about 8337 files (including tmp, pyc, test, .svn files): $ time tree -fi > /dev/null real 0m0.170s user 0m0.044s sys 0m0.123s $ time ls -lR > /dev/null real 0m0.292s user 0m0.138s sys 0m0.152s $ time find . > /dev/null real 0m0.074s user 0m0.017s sys 0m0.056s $ tree appears to be faster than ls -lR (though ls -R is faster than tree, but it does not give full paths). find is the fastest. Can anyone think of a faster and/or better approach? On Windows, I may simply ship a 32-bit binary tree.exe or ls.exe if necessary. Update 1: Added find

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• SQL select all items of an owner from an item-to-owner table

  - by kdobrev

  I have a table bike_to_owner. I would like to select current items owned by a specific user. Table structure is CREATE TABLE IF NOT EXISTS `bike_to_owner` ( `bike_id` int(10) unsigned NOT NULL, `user_id` int(10) unsigned NOT NULL, `last_change_date` date NOT NULL, PRIMARY KEY (`bike_id`,`user_id`,`last_change_date`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci; In the profile page of the user I would like to display all his/her current possessions. I wrote this statement: SELECT `bike_id`,`user_id`,max(last_change_date) FROM `bike_to_owner` WHERE `user_id` = 3 group by `last_change_date` but i'm not quite sure it works correctly in all cases. Can you please verify this is correct and if not suggest me something better. Using php/mysql. Thanks in advance!

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• Spring Web application internal visual monitoring heap space and permgen.

  - by Veniamin

  If I have created web application used Spring framework(based on maven), can I include some module/dependency/plugin into my app to monitor Heap space, Permgen, etc. It whould be greate to get some charts output likes as in VisuaVM. For example: http://localhost:8080/monitoring = Including something likes VisualVM I have found next dependency without link to repo: <dependency> <groupId>com.sun.tools.visualvm</groupId> <artifactId>core</artifactId> <version>1.3.3</version> </dependency> How to use it?

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• Combine SQL statement

  - by ninumedia

  I have 3 tables (follows, postings, users) follows has 2 fields - profile_id , following_id postings has 3 fields - post_id, profile_id, content users has 3 fields - profile_id, first_name, last_name I have a follows.profile_id value of 1 that I want to match against. When I run the SQL statement below I get the 1st step in obtaining the correct data. However, I now want to match the postings.profile_id of this resulting set against the users table so each of the names (first and last name) are displayed as well for all the listed postings. Thank you for your help! :) Ex: SELECT * FROM follows JOIN postings ON follows.following_id = postings.profile_id WHERE follows.profile_id = 1

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• Fastest XML parser for small, simple documents in Java

  - by Varkhan

  I have to objectify very simple and small XML documents (less than 1k, and it's almost SGML: no namespaces, plain UTF-8, you name it...), read from a stream, in Java. I am using JAXP to process the data from my stream into a Document object. I have tried Xerces, it's way too big and slow... I am using Dom4j, but I am still spending way too much time in org.dom4j.io.SAXReader. Does anybody out there have any suggestion on a faster, more efficient implementation, keeping in mind I have very tough CPU and memory constraints? [Edit 1] Keep in mind that my documents are very small, so the overhead of staring the parser can be important. For instance I am spending as much time in org.xml.sax.helpers.XMLReaderFactory.createXMLReader as in org.dom4j.io.SAXReader.read [Edit 2] The result has to be in Dom format, as I pass the document to decision tools that do arbitrary processing on it, like switching code based on the value of arbitrary XPaths, but also extracting lists of values packed as children of a predefined node. [Edit 3] In any case I eventually need to load/parse the complete document, since all the information it contains is going to be used at some point. (This question is related to, but different from, http://stackoverflow.com/questions/373833/best-xml-parser-for-java )

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• How to find the worst performing queries in MS SQL Server 2008?

  - by Thomas Bratt

  How to find the worst performing queries in MS SQL Server 2008? I found the following example but it does not seem to work: SELECT TOP 5 obj.name, max_logical_reads, max_elapsed_time FROM sys.dm_exec_query_stats a CROSS APPLY sys.dm_exec_sql_text(sql_handle) hnd INNER JOIN sys.sysobjects obj on hnd.objectid = obj.id ORDER BY max_logical_reads DESC Taken from: http://www.sqlservercurry.com/2010/03/top-5-costly-stored-procedures-in-sql.html

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• Compare values in serialized column in Doctrine with Query Builder

  - by ReynierPM

  I'm building a FormType for a Symfony2 project but I need some Query Builder on the field since I need to compare some values with the one stored on DB and show the results. This is what I have: .... ->add('servicio', 'entity', array( 'mapped' => false, 'class' => 'ComunBundle:TipoServicio', 'property' => 'nombre', 'required' => true, 'label' => false, 'expanded' => true, 'multiple' => true, 'query_builder' => function (EntityRepository $er) { return $er->createQueryBuilder('ts') ->where('ts.tipo_usuario = (:tipo)') ->setParameter('tipo', 1); } )) .... But tipo_usuario at DB table is stored as serialized text for example: record1: value1 | a:1:{i:0;s:1:"1";} record2: value2 | a:4:{i:0;s:1:"1";i:1;s:1:"2";i:2;s:1:"3";i:3;s:1:"4";} I'll have two different forms (I don't know how to pass the Request to a form) in the first one I'll only show the first record and for the second one the first and second record for example: First form will show: checkbox: value1 Second form will show: checkbox: value1 checkbox: value2 I achieve this? Any help?

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• MySQL 5.1.41 leading zero is deleted

  - by iggnition

  Hello, I have a MySQL database where i want to store phonenumbers among other things. The fieldtype is INT(10) When I try to insert a number starting with a 0, like 0504042858 it's stored like 504042858. This only happens with zeros when the number start with any other number it's stored correctly. What am I doing wrong?

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• MySQL - get all unique values of a column, check if has a specific value

  - by gamers2000

  First off - apologies for the poor title, I have no idea how to describe it in a one-liner. I have a table - snippet is below. mysql> select * from playlistfiles; +-----------------------+--------------+-----------+ | FileName | PlaylistName | FileIndex | +-----------------------+--------------+-----------+ | File1 | Image1 | 0 | | File1 | Video1 | 2 | | File2 | Video1 | 0 | | File3 | Video1 | 1 | | File4 | Image1 | 1 | | File4 | Video1 | 3 | +-----------------------+--------------+-----------+ 6 rows in set (0.00 sec) What I need to do is to get all the FileNames and whether the file is in a playlist or not, as well as order them by FileIndex i.e. for the Image1 playlist, the output should be +-----------------------+------------+-----------+ | FileName | InPlaylist | FileIndex | +-----------------------+------------+-----------+ | File1 | 1 | 0 | | File2 | 0 | Null | | File3 | 0 | Null | | File4 | 1 | 1 | +-----------------------+------------+-----------+ and Video1 would be +-----------------------+------------+-----------+ | FileName | InPlaylist | FileIndex | +-----------------------+------------+-----------+ | File2 | 1 | 0 | | File3 | 1 | 1 | | File1 | 1 | 2 | | File4 | 1 | 3 | +-----------------------+------------+-----------+ In short, I need to be able to get all the unique FileNames from the table, and check if it is in a given table and if so, order it by FileIndex.

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• How do you compare the performace of valarrays vs built-in arrays?

  - by Sergio

  Is there a significant penalty in using the more user-friendly valarray over built-in arrays? Do you know of some benchmarks?

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• Summing Row in SQL query for time range

  - by user3703334

  I'm trying to group a large amount of data into smaller bundles. Currently the code for my query is as follows SELECT [DateTime] ,[KW] FROM [POWER] WHERE datetime >= '2014-04-14 06:00:00' and datetime < '2014-04-21 06:00:00' ORDER BY datetime which gives me DateTime KW 4/14/2014 6:00:02.0 1947 4/14/2014 6:00:15.0 1946 4/14/2014 6:00:23.0 1947 4/14/2014 6:00:32.0 1011 4/14/2014 6:00:43.0 601 4/14/2014 6:00:52.0 585 4/14/2014 6:01:02.0 582 4/14/2014 6:01:12.0 580 4/14/2014 6:01:21.0 579 4/14/2014 6:01:32.0 579 4/14/2014 6:01:44.0 578 4/14/2014 6:01:53.0 578 4/14/2014 6:02:01.0 577 4/14/2014 6:02:12.0 577 4/14/2014 6:02:22.0 577 4/14/2014 6:02:32.0 576 4/14/2014 6:02:42.0 578 4/14/2014 6:02:52.0 577 4/14/2014 6:03:02.0 577 4/14/2014 6:03:12.0 577 4/14/2014 6:03:22.0 578 . . . . 4/21/2014 5:59:55.0 11 Now there is a reading every 10 seconds from a substation. Now I want to group this data into hourly readings. Thus 00:00-01:00 = sum([KW]] for where datetime >= '^date^ 00:00:00' and datetime < '^date^ 01:00:00' I've tried using a convert to change the datetime into date and time field and then only to add all the time fields together with no success. Can someone please assist me, I'm not sure what is right way of doing this. Thanks ADDED Ok so the spilt between Datetime is working nicely, but as if I add a SUM([KW]) function SQL gives an error. And if I include any of the group functions it also nags. Below is what works, I still need to sum the KW per the grouping of hours. I've tried using Group By Hour and Group by DATEPART(Hour,[DateTime]) Both didn't work. SELECT DATEPART(Hour,[DateTime]) Hour ,DATEPART(Day,[DateTime]) Day ,DATEPART(Month,[DateTime]) Month ,([KVAReal]) ,([KVAr]) ,([KW]) FROM [POWER].[dbo].[IT10t_PAC3200] WHERE datetime >= '2014-04-14 06:00:00' and datetime < '2014-04-21 06:00:00' order by datetime

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• How to run sql from a .net application against sqlserver and get output like with SQL Management Stu

  - by Rory

  I'd like my app to run sql files and receive the results output as if the sql was run from SQL Management Studio with results to text. i.e. nicely formatted recordsets, printed messages, rows affected, errors, running multiple batches separated by GO statements, etc. Any suggestions how to do this without building it from scratch on top of a normal SQL connection?

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• Best practice for handling memory leaks in large Java projects?

  - by knorv

  In almost all larger Java projects I've been involved with I've noticed that the quality of service of the application degrades with the uptime of the container. This is most probably due to memory leaks in the code. The correct way to solve this problem is obviously to trace back to the root cause of the problem and fix the leaks in the code. The quick and dirty way of solving the problem is simply restarting Tomcat (or whichever servlet container you're using). These are my three questions: Assume that you choose to solve the problem by tracing the root cause of the problem (the memory leaks), how would you collect data to zoom in on the problem? Assume that you choose the quick and dirty way of speeding things up by simply restarting the container, how would you collect data to choose the optimal restart cycle? Have you been able to deploy and run projects over an extended period of time without ever restarting the servlet container to regain snappiness? Or is an occasional servlet restart something that one has to simply accept?

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• Select distinct users with referrals

  - by Mark

  I have a bunch of Users. Since Django doesn't really let me extend the default User model, they each have Profiles. The Profiles have a referred_by field (a FK to User). I'm trying to get a list of Users with = 1 referral. Here's what I've got so far Profile.objects.filter(referred_by__isnull=False).values_list('referred_by', flat=True) Which gives me a list of IDs of the users who have referrals... but I need it to be distinct, and I want the User object, not their ID. Or better yet, it would be nice if it could return the number of referrals a user has. Any ideas?

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• Tracking down slow managed DLL loading

  - by Alex K

  I am faced with the following issue and at this point I feel like I'm severely lacking some sort of tool, I just don't know what that tool is, or what exactly it should be doing. Here is the setup: I have a 3rd party DLL that has to be registered in GAC. This all works fine and good on pretty much every machine our software was deployed on before. But now we got 2 machines, seemingly identical to the ones we know work (they are cloned from the same image and stuffed with the same hardware, so pretty much the only difference is software settings, over which I went over and over, and they seem fine). Now the problem, the DLL in GAC takes a very long time to load. At least I believe this is the issue, what I can say definitively is that instantiating a single class from that DLL is the slow part. Once it is loaded, thing fly as they always have. But while on known-good machines the DLL loads so fast that a timestamp in the log doesn't even change, on these 2 machines it take over 1min to load. Knowns: I have no access to the source, so I can't debug through the DLL. Our app is the only one that uses it (so shouldn't be simultaneous access issues). There is only one version of this DLL in existance, so it shouldn't be a matter of version conflict. The GAC reference is being used (if I uninstall the DLL from GAC, an exception will be thrown about the missing GAC reference). Could someone with a greater skill in debug-fu suggest what I can do to track down the root cause of this issue?

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• WCF data services (OData), query with inheritance limitation?

  - by Mathieu Hétu

  Project: WCF Data service using internally EF4 CTP5 Code-First approach. I configured entities with inheritance (TPH). See previous question on this topic: Previous question about multiple entities- same table The mapping works well, and unit test over EF4 confirms that queries runs smoothly. My entities looks like this: ContactBase (abstract) Customer (inherits from ContactBase), this entity has also several Navigation properties toward other entities Resource (inherits from ContactBase) I have configured a discriminator, so both Customer and Resource map to the same table. Again, everythings works fine on the Ef4 point of view (unit tests all greens!) However, when exposing this DBContext over WCF Data services, I get: - CustomerBases sets exposed (Customers and Resources sets seems hidden, is it by design?) - When I query over Odata on Customers, I get this error: Navigation Properties are not supported on derived entity types. Entity Set 'ContactBases' has a instance of type 'CodeFirstNamespace.Customer', which is an derived entity type and has navigation properties. Please remove all the navigation properties from type 'CodeFirstNamespace.Customer'. Stacktrace: at System.Data.Services.Serializers.SyndicationSerializer.WriteObjectProperties(IExpandedResult expanded, Object customObject, ResourceType resourceType, Uri absoluteUri, String relativeUri, SyndicationItem item, DictionaryContent content, EpmSourcePathSegment currentSourceRoot) at System.Data.Services.Serializers.SyndicationSerializer.WriteEntryElement(IExpandedResult expanded, Object element, ResourceType expectedType, Uri absoluteUri, String relativeUri, SyndicationItem target) at System.Data.Services.Serializers.SyndicationSerializer.<DeferredFeedItems>d__b.MoveNext() at System.ServiceModel.Syndication.Atom10FeedFormatter.WriteItems(XmlWriter writer, IEnumerable`1 items, Uri feedBaseUri) at System.ServiceModel.Syndication.Atom10FeedFormatter.WriteFeedTo(XmlWriter writer, SyndicationFeed feed, Boolean isSourceFeed) at System.ServiceModel.Syndication.Atom10FeedFormatter.WriteFeed(XmlWriter writer) at System.ServiceModel.Syndication.Atom10FeedFormatter.WriteTo(XmlWriter writer) at System.Data.Services.Serializers.SyndicationSerializer.WriteTopLevelElements(IExpandedResult expanded, IEnumerator elements, Boolean hasMoved) at System.Data.Services.Serializers.Serializer.WriteRequest(IEnumerator queryResults, Boolean hasMoved) at System.Data.Services.ResponseBodyWriter.Write(Stream stream) Seems like a limitation of WCF Data services... is it? Not much documentation can be found on the web about WCF Data services (OData) and inheritance specifications. How can I overpass this exception? I need these navigation properties on derived entities, and inheritance seems the only way to provide mapping of 2 entites on the same table with Ef4 CTP5... Any thoughts?

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• Need mySQL TIMESTAMP for begining of the current week or any given date?

  - by Kenan

  Hi, I need mySQL timestamp for start of current week or any given date, if week starts with monday? I'm trying something like: SELECT UNIX_TIMESTAMP(CONCAT( DATE_SUB(CURDATE(), INTERVAL WEEKDAY(DATE_SUB(CURDATE(), INTERVAL 7 DAY)) DAY), ' 00:00:00')) as start

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• What's the good of IDE's auto generated @override annotation ?

  - by Tony

  I am using eclipse , when I use shortcut to generate override implementations , there is an override annotation up there , I am using JDK 6 , this is all right , but under JDK 5 this annotation will cause an error, so I want to ask , if this annotation is completely useless ? Will compiler do some kind of optimization using this annotation ?

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• C++ program runs slow in VS2008

  - by Nima

  I have a program written in C++, that opens a binary file(test.bin), reads it object by object, and puts each object into a new file (it opens the new file, writes into it(append), and closes it). I use fopen/fclose, fread and fwrite. test.bin contains 20,000 objects. This program runs under linux with g++ in 1 sec but in VS2008 in debug/release mode in 1min! There are reasons why I don't do them in batches or don't keep them in memory or any other kind of optimizations. I just wonder why it is that much slow under windows. Thanks,

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• Python re module becomes 20 times slower when called on greater than 101 different regex

  - by Wiil

  My problem is about parsing log files and removing variable parts on each lines to be able to group them. For instance: s = re.sub(r'(?i)User [_0-9A-z]+ is ', r"User .. is ", s) s = re.sub(r'(?i)Message rejected because : (.*?) \(.+\)', r'Message rejected because : \1 (...)', s) I have about 120+ matching rules like those above. I have found no performances issues while searching successively on 100 different regex. But a huge slow down comes when applying 101 regex. Exact same behavior happens when replacing my rules set by for a in range(100): s = re.sub(r'(?i)caught here'+str(a)+':.+', r'( ... )', s) Got 20 times slower when putting range(101) instead. # range(100) % ./dashlog.py file.bz2 == Took 2.1 seconds. == # range(101) % ./dashlog.py file.bz2 == Took 47.6 seconds. == Why such thing is happening ? And is there any known workaround ? (Happens on Python 2.6.6/2.7.2 on Linux/Windows.)

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• Unknown Column?

  - by Kenny

  ok im trying to get mutual friends between these Two users, user1 and user92 This is the sql that is successful in displaying them SELECT IF(user_a = 1 OR user_a = 92, user_b, user_a) friend FROM friendship WHERE (user_a = 1 OR user_a = 92) OR (user_b = 1 OR user_b = 92) GROUP BY 1 HAVING COUNT(*) > 1 THis is how it looks friend 61 72 73 74 75 76 77 78 79 80 81 So now i want to select all users after the number 72, and i try to do it with this sql but its not working? It gives me the error, "unknown coulum name friend in where clause" SELECT IF(user_a = 1 OR user_a = 92, user_b, user_a) friend FROM friendship WHERE friend > 72 and (user_a = 1 OR user_a = 92) OR (user_b = 1 OR user_b = 92) GROUP BY 1 HAVING COUNT(*) > 1 what am i doing wrong? or what is the correct way?? thx

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