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• mysql first record retrieval

  - by Sammy

  While very easy to do in Perl or PHP, I cannot figure how to use mysql only to extract the first unique occurence of a record. For example, given the following table: Name Date Time Sale John 2010-09-12 10:22:22 500 Bill 2010-08-12 09:22:37 2000 John 2010-09-13 10:22:22 500 Sue 2010-09-01 09:07:21 1000 Bill 2010-07-25 11:23:23 2000 Sue 2010-06-24 13:23:45 1000 I would like to extract the first record for each individual in asc time order. After sorting the table is ascending time order, I need to extract the first unique record by name. So the output would be : Name Date Time Sale John 2010-09-12 10:22:22 500 Bill 2010-07-25 11:23:23 2000 Sue 2010-06-24 13:23:45 1000 Is this doable in an easy fashion with mySQL? Thanks, Sammy

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• Creating thousands of records in Rails

  - by willCosgrove

  Let me set the stage: My application deals with gift cards. When we create cards they have to have a unique string that the user can use to redeem it with. So when someone orders our gift cards, like a retailer, we need to make a lot of new card objects and store them in the DB. With that in mind, I'm trying to see how quickly I can have my application generate 100,000 Cards. Database expert, I am not, so I need someone to explain this little phenomena: When I create 1000 Cards, it takes 5 seconds. When I create 100,000 cards it should take 500 seconds right? Now I know what you're wanting to see, the card creation method I'm using, because the first assumption would be that it's getting slower because it's checking the uniqueness of a bunch of cards, more as it goes along. But I can show you my rake task desc "Creates cards for a retailer" task :order_cards, [:number_of_cards, :value, :retailer_name] => :environment do |t, args| t = Time.now puts "Searching for retailer" @retailer = Retailer.find_by_name(args[:retailer_name]) puts "Retailer found" puts "Generating codes" value = args[:value].to_i number_of_cards = args[:number_of_cards].to_i codes = [] top_off_codes(codes, number_of_cards) while codes != codes.uniq codes.uniq! top_off_codes(codes, number_of_cards) end stored_codes = Card.all.collect do |c| c.code end while codes != (codes - stored_codes) codes -= stored_codes top_off_codes(codes, number_of_cards) end puts "Codes are unique and generated" puts "Creating bundle" @bundle = @retailer.bundles.create!(:value => value) puts "Bundle created" puts "Creating cards" @bundle.transaction do codes.each do |code| @bundle.cards.create!(:code => code) end end puts "Cards generated in #{Time.now - t}s" end def top_off_codes(codes, intended_number) (intended_number - codes.size).times do codes << ReadableRandom.get(CODE_LENGTH) end end I'm using a gem called readable_random for the unique code. So if you read through all of that code, you'll see that it does all of it's uniqueness testing before it ever starts creating cards. It also writes status updates to the screen while it's running, and it always sits for a while at creating. Meanwhile it flies through the uniqueness tests. So my question to the stackoverflow community is: Why is my database slowing down as I add more cards? Why is this not a linear function in regards to time per card? I'm sure the answer is simple and I'm just a moron who knows nothing about data storage. And if anyone has any suggestions, how would you optimize this method, and how fast do you think you could get it to create 100,000 cards? (When I plotted out my times on a graph and did a quick curve fit to get my line formula, I calculated how long it would take to create 100,000 cards with my current code and it says 5.5 hours. That maybe completely wrong, I'm not sure. But if it stays on the line I curve fitted, it would be right around there.)

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• Return pre-UPDATE column values in PostgreSQL without using triggers, functions or other "magic"

  - by Python Larry

  I have a related question, but this is another part of MY puzzle. I would like to get the OLD VALUE of a Column from a Row that was UPDATEd... WITHOUT using Triggers (nor Stored Procedures, nor any other extra, non-SQL/-query entities). The query I have is like this: UPDATE my_table SET processing_by = our_id_info -- unique to this instance WHERE trans_nbr IN ( SELECT trans_nbr FROM my_table GROUP BY trans_nbr HAVING COUNT(trans_nbr) > 1 LIMIT our_limit_to_have_single_process_grab ) RETURNING row_id If I could do "FOR UPDATE ON my_table" at the end of the subquery, that'd be devine (and fix my other question/problem). But, that won't work: can't have this AND a "GROUP BY" (which is necessary for figuring out the COUNT of trans_nbr's). Then I could just take those trans_nbr's and do a query first to get the (soon-to-be-) former processing_by values. I've tried doing like: UPDATE my_table SET processing_by = our_id_info -- unique to this instance FROM my_table old_my_table JOIN ( SELECT trans_nbr FROM my_table GROUP BY trans_nbr HAVING COUNT(trans_nbr) > 1 LIMIT our_limit_to_have_single_process_grab ) sub_my_table ON old_my_table.trans_nbr = sub_my_table.trans_nbr WHERE my_table.trans_nbr = sub_my_table.trans_nbr AND my_table.processing_by = old_my_table.processing_by RETURNING my_table.row_id, my_table.processing_by, old_my_table.processing_by But that can't work; "old_my_table" is not viewable outside of the join; the RETURNING clause is blind to it. I've long since lost count of all the attempts I've made; I have been researching this for literally hours. If I could just find a bullet-proof way to lock the rows in my subquery - and ONLY those rows, and WHEN the subquery happens - all the concurrency issues I'm trying to avoid disappear... UPDATE: [WIPES EGG OFF FACE] Okay, so I had a typo in the non-generic code of the above that I wrote "doesn't work"; it does... thanks to Erwin Brandstetter, below, who stated it would, I re-did it (after a night's sleep, refreshed eyes, and a banana for bfast). Since it took me so long/hard to find this sort of solution, perhaps my embarrassment is worth it? At least this is on SO for posterity now... : What I now have (that works) is like this: UPDATE my_table SET processing_by = our_id_info -- unique to this instance FROM my_table AS old_my_table WHERE trans_nbr IN ( SELECT trans_nbr FROM my_table GROUP BY trans_nbr HAVING COUNT(*) > 1 LIMIT our_limit_to_have_single_process_grab ) AND my_table.row_id = old_my_table.row_id RETURNING my_table.row_id, my_table.processing_by, old_my_table.processing_by AS old_processing_by The COUNT(*) is per a suggestion from Flimzy in a comment on my other (linked above) question. (I was more specific than necessary. [In this instance.])

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• Fast permutation -> number -> permutation mapping algorithms

  - by ijw

  I have n elements. For the sake of an example, let's say, 7 elements, 1234567. I know there are 7! = 5040 permutations possible of these 7 elements. I want a fast algorithm comprising two functions: f(number) maps a number between 0 and 5039 to a unique permutation, and f'(permutation) maps the permutation back to the number that it was generated from. I don't care about the correspondence between number and permutation, providing each permutation has its own unique number. So, for instance, I might have functions where f(0) = '1234567' f'('1234567') = 0 The fastest algorithm that comes to mind is to enumerate all permutations and create a lookup table in both directions, so that, once the tables are created, f(0) would be O(1) and f('1234567') would be a lookup on a string. However, this is memory hungry, particularly when n becomes large. Can anyone propose another algorithm that would work quickly and without the memory disadvantage?

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• Symfony FK Constraint Issue

  - by Daniel Hertz

  Hello! So I have a table schema that has users who can be friends. User: actAs: { Timestampable: ~ } columns: name: { type: string(255), notnull: true } email: { type: string(255), notnull: true, unique: true } nickname: { type: string(255), unique: true } password: { type: string(300), notnull: true } image: { type: string(255) } FriendsWith: actAs: { Timestampable: ~ } columns: friend1_id: { type: integer, primary: true } friend2_id: { type: integer, primary: true } relations: User: { onDelete: CASCADE, local: friend1_id, foreign: id } User: { onDelete: CASCADE, local: friend2_id, foreign: id } It builds the database correctly, but when I try to insert test data like: User: user1: name: Danny Gurt email: [email protected] nickname: danny password: test1 user2: name: Adrian Soian email: [email protected] nickname: adrian password: test1 FriendsWith: friendship1: friend1_id: user1 friend2_id: user2 I get this integrity constraint problem: SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails (`krowdd`.`friends_with`, CONSTRAINT `friends_with_ibfk_1` FOREIGN KEY (`friend1_id`) REFERENCES `user` (`id`) ON DELETE CASCADE) Any ideas? Thanks!

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• mysql index optimization for a table with multiple indexes that index some of the same columns

  - by Sean

  I have a table that stores some basic data about visitor sessions on third party web sites. This is its structure: id, site_id, unixtime, unixtime_last, ip_address, uid There are four indexes: id, site_id/unixtime, site_id/ip_address, and site_id/uid There are many different types of ways that we query this table, and all of them are specific to the site_id. The index with unixtime is used to display the list of visitors for a given date or time range. The other two are used to find all visits from an IP address or a "uid" (a unique cookie value created for each visitor), as well as determining if this is a new visitor or a returning visitor. Obviously storing site_id inside 3 indexes is inefficient for both write speed and storage, but I see no way around it, since I need to be able to quickly query this data for a given specific site_id. Any ideas on making this more efficient? I don't really understand B-trees besides some very basic stuff, but it's more efficient to have the left-most column of an index be the one with the least variance - correct? Because I considered having the site_id being the second column of the index for both ip_address and uid but I think that would make the index less efficient since the IP and UID are going to vary more than the site ID will, because we only have about 8000 unique sites per database server, but millions of unique visitors across all ~8000 sites on a daily basis. I've also considered removing site_id from the IP and UID indexes completely, since the chances of the same visitor going to multiple sites that share the same database server are quite small, but in cases where this does happen, I fear it could be quite slow to determine if this is a new visitor to this site_id or not. The query would be something like: select id from sessions where uid = 'value' and site_id = 123 limit 1 ... so if this visitor had visited this site before, it would only need to find one row with this site_id before it stopped. This wouldn't be super fast necessarily, but acceptably fast. But say we have a site that gets 500,000 visitors a day, and a particular visitor loves this site and goes there 10 times a day. Now they happen to hit another site on the same database server for the first time. The above query could take quite a long time to search through all of the potentially thousands of rows for this UID, scattered all over the disk, since it wouldn't be finding one for this site ID. Any insight on making this as efficient as possible would be appreciated :) Update - this is a MyISAM table with MySQL 5.0. My concerns are both with performance as well as storage space. This table is both read and write heavy. If I had to choose between performance and storage, my biggest concern is performance - but both are important. We use memcached heavily in all areas of our service, but that's not an excuse to not care about the database design. I want the database to be as efficient as possible.

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• Handling update errors in multiple records in the TClientDataset's ReconcileError method

  - by Fabio Gomes

  I'm trying to use the ReconcileError event to allow the user to correct the data after an update error which occurred in a specific record among others. Example: I have a dataset with one field and 3 records, this field have a unique constraint on the database, then I change one value to conflict when it reaches the database, then I call ApplyUpdates on the Dataset. This will generate an error (violation of unique constraint) in the provider and abort the applyupdates process, returning raAbort in the Action var of the ReconcileError method. In the ReconcileError method I tryied to use: Action := HandleReconcileError(aDataSet, UpdateKind, E); ** EDIT ** After debugging and dumping the DataSet records which were returned from the server, I noticed that there are 2 records in this Dataset, the first is the Old record and the second have all the changes I made to the first record. I'm a bit confused, will I always get this DataSet with 2 records? I thought that it should have only one record with the Old/New values. Thanks.

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• .NET SortedDictionary But Sorted By Values

  - by Michael Covelli

  I need a data structure that acts like a SortedDictionary<int, double> but is sorted based on the values rather than the keys. I need it to take about 1-2 microseconds to add and remove items when we have about 3000 items in the dictionary. My first thought was simply to switch the keys and values in my code. This very nearly works. I can add and remove elements in about 1.2 microseconds in my testing by doing this. But the keys have to be unique in a SortedDictionary so that means that values in my inverse dictionary would have to be unique. And there are some cases where they may not be. Any ideas of something in the .NET libraries already that would work for me?

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• SEO Canonical Issue resolution on iis

  - by kacalapy

  i have a site running on IIS that i have Canonical Issue with. the error is: The page with URL "http://www.site.org/images/join_forum.gif" can also be accessed by using URL "https://www.site.org/images/join_forum.gif".Search engines identify unique pages by using URLs. When a single page can be accessed by using any one of multiple URLs, a search engine assumes that there are multiple unique pages. Use a single URL to reference a page to prevent dilution of page relevance. You can prevent dilution by following a standard URL format. how can i resolve this?

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• I'm using spring, hibernate and mysql. How can I let my app create the table automatically.

  - by Yousui

  Hi guys, I'm using spring, all my annotated entity class information are put in the ApplicationContext.xml. I'm using a MySql database, now how can I use the SchemaExport function in hibernate to create the tables? My application can't create the table automatically, though i have set <prop key="hbm2ddl.auto">create</prop>. This is my ApplicationContext.xml: <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop" xmlns:context="http://www.springframework.org/schema/context" xmlns:jdbc="http://www.springframework.org/schema/jdbc" xmlns:jee="http://www.springframework.org/schema/jee" xmlns:tx="http://www.springframework.org/schema/tx" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc-3.0.xsd http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd"> <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource"> <property name="driverClassName" value="com.mysql.jdbc.Driver" /> <property name="url" value="jdbc:mysql:///edde" /> <property name="username" value="root" /> <property name="password" value="" /> </bean> <bean id="sessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean"> <property name="dataSource" ref="dataSource" /> <property name="annotatedClasses"> <list> <value>com.edde.Book</value> </list> </property> <property name="hibernateProperties"> <props> <prop key="current_session_context_class">thread</prop> <prop key="show_sql">true</prop> <prop key="hbm2ddl.auto">create</prop> <prop key="hibernate.show_sql">true</prop> <prop key="hibernate.use_sql_comments">true</prop> <prop key="hibernate.format_sql">true</prop> </props> </property> </bean> <bean id="transactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager"> <property name="sessionFactory" ref="sessionFactory" /> </bean> <tx:annotation-driven transaction-manager="transactionManager" /> <bean id="bookDao" class="com.edde.BookDao"> <property name="sessionFactory" ref="sessionFactory"></property> </bean> <bean id="bookService" class="com.edde.BookServiceImpl"> <property name="dao" ref="bookDao"></property> </bean> </beans> This is my test application: package com.edde; import org.springframework.context.support.ClassPathXmlApplicationContext; public class Test { /** * @param args */ public static void main(String[] args) { ClassPathXmlApplicationContext factory = new ClassPathXmlApplicationContext("applicationContext.xml"); BookService service = (BookService) factory.getBean("bookService"); Book book = new Book(); book.setBookName("great book"); service.saveBook(book); } } When I run my app, I get this error: 2010-05-20 17:25:20,777 DEBUG [org.hibernate.SQL] - /* insert com.edde.Book */ insert into Book (author, bookName, publication) values (?, ?, ?) Hibernate: /* insert com.edde.Book */ insert into Book (author, bookName, publication) values (?, ?, ?) 2010-05-20 17:25:20,809 DEBUG [org.hibernate.jdbc.AbstractBatcher] - about to close PreparedStatement (open PreparedStatements: 1, globally: 1) 2010-05-20 17:25:20,809 DEBUG [org.hibernate.util.JDBCExceptionReporter] - could not insert: [com.edde.Book] [/* insert com.edde.Book */ insert into Book (author, bookName, publication) values (?, ?, ?)] com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Table 'edde.book' doesn't exist at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) at java.lang.reflect.Constructor.newInstance(Constructor.java:513) at com.mysql.jdbc.Util.handleNewInstance(Util.java:409) at com.mysql.jdbc.Util.getInstance(Util.java:384) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1054) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3562) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3494) at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1960) at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2114) at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2696) at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2105) at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2398) at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2316) at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2301) at org.hibernate.id.IdentityGenerator$GetGeneratedKeysDelegate.executeAndExtract(IdentityGenerator.java:94) at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:57) at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2329) at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2836) at org.hibernate.action.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:71) at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:268) at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:321) at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:204) at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:130) at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:210) at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:56) at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:195) at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:50) at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93) at org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:705) at org.hibernate.impl.SessionImpl.save(SessionImpl.java:693) at org.hibernate.impl.SessionImpl.save(SessionImpl.java:689) at org.springframework.orm.hibernate3.HibernateTemplate$12.doInHibernate(HibernateTemplate.java:686) at org.springframework.orm.hibernate3.HibernateTemplate$12.doInHibernate(HibernateTemplate.java:1) at org.springframework.orm.hibernate3.HibernateTemplate.doExecute(HibernateTemplate.java:406) at org.springframework.orm.hibernate3.HibernateTemplate.executeWithNativeSession(HibernateTemplate.java:374) at org.springframework.orm.hibernate3.HibernateTemplate.save(HibernateTemplate.java:683) at com.edde.BookDao.insertBook(BookDao.java:18) at com.edde.BookServiceImpl.saveBook(BookServiceImpl.java:34) at com.edde.Test.main(Test.java:17) 2010-05-20 17:25:20,809 WARN [org.hibernate.util.JDBCExceptionReporter] - SQL Error: 1146, SQLState: 42S02 2010-05-20 17:25:20,809 ERROR [org.hibernate.util.JDBCExceptionReporter] - Table 'edde.book' doesn't exist 2010-05-20 17:25:20,809 DEBUG [org.springframework.orm.hibernate3.SessionFactoryUtils] - Closing Hibernate Session 2010-05-20 17:25:20,809 DEBUG [org.hibernate.jdbc.ConnectionManager] - releasing JDBC connection [ (open PreparedStatements: 0, globally: 0) (open ResultSets: 0, globally: 0)] 2010-05-20 17:25:20,809 DEBUG [org.hibernate.jdbc.ConnectionManager] - transaction completed on session with on_close connection release mode; be sure to close the session to release JDBC resources! Exception in thread "main" org.springframework.dao.InvalidDataAccessResourceUsageException: could not insert: [com.edde.Book]; SQL [/* insert com.edde.Book */ insert into Book (author, bookName, publication) values (?, ?, ?)]; nested exception is org.hibernate.exception.SQLGrammarException: could not insert: [com.edde.Book] at org.springframework.orm.hibernate3.SessionFactoryUtils.convertHibernateAccessException(SessionFactoryUtils.java:629) at org.springframework.orm.hibernate3.HibernateAccessor.convertHibernateAccessException(HibernateAccessor.java:412) at org.springframework.orm.hibernate3.HibernateTemplate.doExecute(HibernateTemplate.java:411) at org.springframework.orm.hibernate3.HibernateTemplate.executeWithNativeSession(HibernateTemplate.java:374) at org.springframework.orm.hibernate3.HibernateTemplate.save(HibernateTemplate.java:683) at com.edde.BookDao.insertBook(BookDao.java:18) at com.edde.BookServiceImpl.saveBook(BookServiceImpl.java:34) at com.edde.Test.main(Test.java:17) Caused by: org.hibernate.exception.SQLGrammarException: could not insert: [com.edde.Book] at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:92) at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66) at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:64) at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2329) at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2836) at org.hibernate.action.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:71) at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:268) at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:321) at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:204) at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:130) at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:210) at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:56) at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:195) at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:50) at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93) at org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:705) at org.hibernate.impl.SessionImpl.save(SessionImpl.java:693) at org.hibernate.impl.SessionImpl.save(SessionImpl.java:689) at org.springframework.orm.hibernate3.HibernateTemplate$12.doInHibernate(HibernateTemplate.java:686) at org.springframework.orm.hibernate3.HibernateTemplate$12.doInHibernate(HibernateTemplate.java:1) at org.springframework.orm.hibernate3.HibernateTemplate.doExecute(HibernateTemplate.java:406) ... 5 more Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Table 'edde.book' doesn't exist at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) at java.lang.reflect.Constructor.newInstance(Constructor.java:513) at com.mysql.jdbc.Util.handleNewInstance(Util.java:409) at com.mysql.jdbc.Util.getInstance(Util.java:384) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1054) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3562) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3494) at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1960) at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2114) at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2696) at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2105) at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2398) at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2316) at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2301) at org.hibernate.id.IdentityGenerator$GetGeneratedKeysDelegate.executeAndExtract(IdentityGenerator.java:94) at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:57) ... 23 more Now my question is: how to create the table automatically? Thanks.

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• How to set a control ID in ListView Template dynamically?

  - by citronas

  A have a ListView that is rendered with multiple items. Now I want to toggle some HTML attributes with JQuery. Therefore it would be best to have access to these elements via an unique ID. But trying to create a "dynamic" and therefore unique ID by <tr runat="server" ID='<%# this.GetUniqueID() %>'> </tr> results in an error that tells me that the ID needs to be simple and cannot be set by a call to a method. I know that I can dynamically create controls in the code-behind and set the ID there. But in this case, I'd rather like to let the content be rendered by the ListView itself. That brings me to the conclusion that the idea of setting a dynically ID in the Template is totally wrong. How can I achieve the desired behaviour?

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• Strategies to use Database Sequences?

  - by Bruno Brant

  Hello all, I have a high-end architecture which receives many requests every second (in fact, it can receive many requests every millisecond). The architecture is designed so that some controls rely on a certain unique id assigned to each request. To create such UID we use a DB2 Sequence. Right now I already understand that this approach is flawed, since using the database is costly, but it makes sense to do so because this value will also be used to log information on the database. My team has just found out an increase of almost 1000% in elapsed time for each transaction, which we are assuming happened because of the sequence. Now I wonder, using sequences will serialize access to my application? Since they have to guarantee that increments works the way they should, they have to, right? So, are there better strategies when using sequences? Please assume that I have no other way of obtaining a unique id other than relying on the database.

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• Doctrine Mssql uniqueidentifier isn't cast as char or nvarchar when retrieved from the database.

  - by Tres

  When I retrieve a record from the database which has a column of type "uniqueidentifier", Doctrine fills it with "null" rather than the unique id from the database. Some research and testing has brought this down to a PDO/dblib driver issue. When directly querying via PDO, null is returned in place of the unique id. For reference, http://trac.doctrine-project.org/ticket/1096, has a bit on this, however, it was updated 11 months ago with no comment for resolution. A way around this, as mentioned at http://bugs.php.net/bug.php?id=24752&edit=1, is to cast the column as a char. However, it doesn't seem Doctrine exposes the native field type outside of generating models which makes it a bit hard to detect uniqueidentifier types and cast them internally when building the sql query. Has anyone found a workaround for this?

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• iPhone: Grouped Table Confusion

  - by senfo

  I'm trying to follow along with this UITableView tutorial and I'm afraid I'm getting confused. What I hope to accomplish is to create a grouped table, which resembles the look and feel of the following image (image source): For each "break" in the table, I assume that I need another section. I understand there is a global NSMutableArray, which acts as the data source to the UITableView. Inside this global array, there are dictionaries for sections and for data, but this is where I start getting confused. Should I create a unique table to store each section in addition to a new table for the rows that are part of that section? In other words, if I have five sections, will I end up with ten unique collections of data (one for each section and one to store the rows related to the section), which all eventually get stored in the global array?

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• MSBuild: Items + Batching + CreateItem + Transforms Question

  - by KeithCS

  I have this bit of an msbuild project that is making me wonder why it the outcome is the way it is. Not that it is causing an issue or anything of the sort, but I would like to try and better my understanding of it. <?xml version="1.0" encoding="utf-8" ?> <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003" DefaultTargets="TestTarget1;TestTarget2" ToolsVersion="3.5"> <ItemGroup> <PathDir Include="C:\RootDir\UniqueDir1"/> <PathDir Include="C:\RootDir\UniqueDir2" /> </ItemGroup> <Target Name="TestTarget1" Outputs="%(PathDir.Identity)"> <PropertyGroup> <RootPath>%(PathDir.Identity)</RootPath> </PropertyGroup> <ItemGroup> <SubDirectory Include="Common1"/> <SubDirectory Include="Common2"/> </ItemGroup> <CreateItem Include="@(SubDirectory->'$(RootPath)\%(Identity)')"> <Output TaskParameter="Include" ItemName="FullPath"/> </CreateItem> <Message Text="@(FullPath)"/> </Target> <Target Name="TestTarget2"> <Message Text="@(FullPath)"/> </Target> </Project> So I have two main paths that are unique, and within each I have two directories with the same names in each of the unique paths. In target1, I am batching against the identity of the items in PathDir, and then performing a transform on item SubDirectory, which contains the common folder names found in the unique directories, to create a new item containing the full paths. So anyways, after that, the output for the targets is as follows: Target 1: C:\RootDir\UniqueDir1\Common1;C:\RootDir\UniqueDir1\Common2 C:\RootDir\UniqueDir2\Common1;C:\RootDir\UniqueDir2\Common2 Target 2: C:\RootDir\UniqueDir1\Common1;C:\RootDir\UniqueDir1\Common2;C:\RootDir\UniqueDir2\Common1;C:\RootDir\UniqueDir2\Common2 So my question I guess is ... why does target1 only display the directories containing the directory it is batching against? I know it probably has to do with batching, but thats all I know.

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• Traceability with XSD

  - by blastthisinferno

  I am trying to let my XML schema handle a little traceability functionality as I'm gathering requirements while I read through some functional specifications. (Not ideal for requirement management, but at least its a start.) What I'm doing is creating a <functionalSpec tag for each functional specification I am currently reading through. I create a <requirement tag for each requirement I find. Since I want to be able to trace where the requirement came from, I create a <trace element with the id of the <functionalSpec element. Instead of allowing myself to enter any plain-old-text in the <functionalSpecId tag, I want the XSD to validate and make sure that I only enter in an id that exists for an existing functional spec. My problem is coming in where it seems the XML Schema W3C Recommendations documentation says that what I want to do is not possible. (about 1/2 way down) {selector} specifies a restricted XPath ([XPath]) expression relative to instances of the element being declared. This must identify a node set of subordinate elements (i.e. contained within the declared element) to which the constraint applies. I'm using Oxygen to create this since I'm fairly new to XSD files, and it gives me the following error: E [Xerces] Identity Constraint error: identity constraint "KeyRef@1045a2" has a keyref which refers to a key or unique that is out of scope. So my question is does anyone know of a way that will allow me to use the same XML structure that I have below through using XSD? Below is the XML file. <?xml version="1.0" encoding="UTF-8" ?> <srs xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="srs req2.xsd" xmlns="srs"> <requirements> <requirement DateCreated="2010-06-11" id="1"> <Text>The system shall...</Text> <trace> <functionalSpecId>B010134</functionalSpecId> </trace> <revisions> <revision date="2010-06-11" num="0"> <description>Initial creation.</description> </revision> </revisions> </requirement> </requirements> <functionalSpecs> <functionalSpec id="B010134" model="Model-T"> <trace> <meeting></meeting> </trace> <revisions> <revision date="2009-07-08" num="0"> <description>Initial creation.</description> </revision> <detailer>Me</detailer> <engineer>Me</engineer> </revisions> </functionalSpec> </functionalSpecs> </srs> Below is the XSD file. <?xml version="1.0" encoding="UTF-8" ?> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="srs" xmlns="srs" xmlns:srs="srs" elementFormDefault="qualified"> <!-- SRS --> <xs:element name="srs" type="SRSType"> </xs:element> <xs:complexType name="SRSType"> <xs:sequence> <xs:element ref="requirements" /> <xs:element ref="functionalSpecs" /> </xs:sequence> </xs:complexType> <!-- Requirements --> <xs:element name="requirements" type="RequirementsType"> <xs:unique name="requirementId"> <xs:selector xpath="srs/requirements/requirement" /> <xs:field xpath="@id" /> </xs:unique> </xs:element> <xs:complexType name="RequirementsType"> <xs:choice maxOccurs="unbounded"> <xs:element name="requirement" type="RequirementType" /> </xs:choice> </xs:complexType> <xs:complexType name="RequirementType"> <xs:complexContent> <xs:extension base="RequirementInfo"> <xs:sequence> <xs:element name="trace" type="TraceType" maxOccurs="unbounded" minOccurs="1" /> <xs:element name="revisions" type="RequirementRevisions" /> </xs:sequence> </xs:extension> </xs:complexContent> </xs:complexType> <xs:complexType name="RequirementRevisions"> <xs:sequence> <xs:element name="revision" type="RevisionInfo" minOccurs="1" maxOccurs="unbounded" /> </xs:sequence> </xs:complexType> <xs:complexType name="RequirementInfo"> <xs:sequence> <xs:element name="Text" type="Description" /> </xs:sequence> <xs:attribute name="DateCreated" type="xs:date" use="required" /> <xs:attribute name="id" type="xs:integer" use="required" /> </xs:complexType> <!-- Functional Specs --> <xs:element name="functionalSpecs" type="FunctionalSpecsType"> <xs:unique name="functionalSpecId"> <xs:selector xpath="srs/functionalSpecs/functionalSpec" /> <xs:field xpath="@id" /> </xs:unique> </xs:element> <xs:complexType name="FunctionalSpecsType"> <xs:choice maxOccurs="unbounded"> <xs:element name="functionalSpec" type="FunctionalSpecType" /> </xs:choice> </xs:complexType> <xs:complexType name="FunctionalSpecType"> <xs:complexContent> <xs:extension base="FunctionalSpecInfo"> <xs:sequence> <xs:element name="trace" type="TraceType" maxOccurs="unbounded" minOccurs="1" /> <xs:element name="revisions" type="FunctionalSpecRevisions" /> </xs:sequence> </xs:extension> </xs:complexContent> </xs:complexType> <xs:complexType name="FunctionalSpecRevisions"> <xs:sequence> <xs:element name="revision" type="RevisionInfo" minOccurs="1" maxOccurs="unbounded" /> <xs:element name="detailer" type="xs:string" /> <xs:element name="engineer" type="xs:string" /> </xs:sequence> </xs:complexType> <xs:complexType name="FunctionalSpecInfo"> <xs:attribute name="id" type="xs:string" use="required" /> <xs:attribute name="model" type="xs:string" use="required" /> </xs:complexType> <!-- Requirements, Functional Specs --> <xs:complexType name="TraceType"> <xs:choice> <xs:element name="requirementId"> <xs:keyref refer="requirementId" name="requirementIdRef"> <xs:selector xpath="srs/requirements/requirement" /> <xs:field xpath="@id" /> </xs:keyref> </xs:element> <xs:element name="functionalSpecId"> <xs:keyref refer="functionalSpecId" name="functionalSpecIdRef"> <xs:selector xpath="srs/functionalSpecs/functionalSpec" /> <xs:field xpath="@id" /> </xs:keyref> </xs:element> <xs:element name="meeting" /> </xs:choice> </xs:complexType> <!-- Common --> <xs:complexType name="RevisionInfo"> <xs:choice> <xs:element name="description" type="Description" /> </xs:choice> <xs:attribute name="date" type="xs:date" use="required" /> <xs:attribute name="num" type="xs:integer" use="required" /> </xs:complexType> <xs:complexType name="Description" mixed="true"> <xs:simpleContent> <xs:extension base="xs:string"> <xs:attribute name="Date" type="xs:date" /> </xs:extension> </xs:simpleContent> </xs:complexType> </xs:schema>

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• Does GIT have evil twin issues?

  - by Senthil A Kumar

  In ClearCase evil twin occurs when two files are found with the same name in two different versions of the directory, and If the element OIDs are different but the names are the same. In GIT the SHA1 id is always unique and file with same name always have different SHA1 id’s. We don’t have a concept of Evil twins, but there are likely cases where there is chance for 2 or more developers creating a file with different contents with same filename in the same directory. During merge, when both files are completely different, there are chances of the developers to keep his changes alone and leave other changes resulting in code loss. Can anyone let me know if there will be issues in GIT similar to ClearCase or sine each SHA1 id is unique there won't be any Evil twin issues in GIT.

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• Analysis services with non normalized table

  - by Uwe

  I have a table with several million rows. Each row represents a user session. There is a column called user which is not unique. There can be multiple sessions per user. I want to use Analysis services to get me the additional properties per user. Example: How many users (unique!) had a session longer than x minutes. How is that possible without changing the database. Note: there is no lookup-table and I cannot create one. What I am able of at the moment is to ask how many sessions were longer then x minutes.

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• paypal redirect on successful checkout

  - by Graeme Leighfield

  I am trying to get my Paypal subscription to redirect to a custom page after a successful checkout. Before submitting to Paypal I overload the submit handler, run my own function (to store details) and return a unique id. I want to attach that id to my return URL. (as a GET or POST var so to speak) I have turned auto redirect "on" in my Paypal sandbox sellers preferences, but it only seems to re-direct to the URL that I HAVE to put in there. using the <input type="hidden" name="return" value="someurl" /> does no seem to work. I want it this way so that I can capture the user information when entered with a "non-paid" flag, then via the IPN I can update that record with a "PAID" flag, and I want to use the unique ID to tie it all together so to speak. Any advice or a different approach is welcomed. Many thanks!

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• EF problem with entity re-ordering and uniqueness constraint

  - by wpfwannabe

  I am using Entity Framework and I've come to an interesting stumbling block. Let's say there is a db table "Item" with "sequence" column of type int (and others of course). Column "sequence" must be unique and it is used for (re)ordering of items. EF maps this table to "Item" class with "sequence" int property. Now let's say I want to swap position of two items by mutually exchanging each other's sequence number. Upon calling SaveChanges() EF throws an exception complaining about "sequence" uniqueness. It probably generates two UPDATEs and the first one probably fails. I assume that plain SQL solution to this issue is using a third UPDATE to introduce a unique sequence value in the process but I am stuck with EF. Any thoughts?

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• Oracle AQ dequeue order

  - by yawn

  A trigger in an Oracle 10g generates upsert and delete messages for a subset of rows in a regular table. These messages consist out of two fields: A unique row id. A non-unique id. When consuming these message I want to impose an order on the deque process that respects the following constraints: Messages must be dequeued in insertion order. Messages belonging to the same id must be dequeued in such a fashion that no other dequeuing process should be able to dequeue a potential successor message (or messages) with this id. Since the messages are generated using a trigger I cannot use groups for this purpose. I am using the Oracle Java interface for AQ. Any pointers on how that could be achieved?

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• checkUnique function?

  - by Chris Leah

  Hey, so I have created a function to check the DB for unique entries, but when I call the function it doesn't seem to work and gives me a fatal error any ideas from the function or do you wish to see the sign up page calling it. Thanks :) //Check for unique entries function checkUnique($table, $field, $compared) { $query = $mysqli->query('SELECT '.$mysqli->real_escape_string($field).' FROM '.$mysqli->real_escape_string($table).' WHERE "'.$mysqli->real_escape_string($field).'" = "'.$mysqli->real_escape_string($compared).'"'); if(!$query){ return TRUE; } else { return FALSE; } } The page calling it..... if (!empty($_POST['username']) && !empty($_POST['password']) && $_POST['password']==$_POST['password_confirm'] && !empty($_POST['email']) && validateEmail($_POST['email']) == TRUE && checkUnqiue('users', 'email', $_POST['email']) == TRUE && checkUnique('users', 'username', $_POST['username']) == TRUE)

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• CakePHP HABTM: Editing one item casuses HABTM row to get recreated, destroys extra data

  - by leo-the-manic

  I'm having trouble with my HABTM relationship in CakePHP. I have two models like so: Department HABTM Location. One large company has many buildings, and each building provides a limited number of services. Each building also has its own webpage, so in addition to the HABTM relationship itself, each HABTM row also has a url field where the user can visit to find additional information about the service they're interested and how it operates at the building they're interested in. I've set up the models like so: <?php class Location extends AppModel { var $name = 'Location'; var $hasAndBelongsToMany = array( 'Department' => array( 'with' => 'DepartmentsLocation', 'unique' => true ) ); } ?> <?php class Department extends AppModel { var $name = 'Department'; var $hasAndBelongsToMany = array( 'Location' => array( 'with' => 'DepartmentsLocation', 'unique' => true ) ); } ?> <?php class DepartmentsLocation extends AppModel { var $name = 'DepartmentsLocation'; var $belongsTo = array( 'Department', 'Location' ); // I'm pretty sure this method is unrelated. It's not being called when this error // occurs. Its purpose is to prevent having two HABTM rows with the same location // and department. function beforeSave() { // kill any existing rows with same associations $this->log(__FILE__ . ": killing existing HABTM rows", LOG_DEBUG); $result = $this->find('all', array("conditions" => array("location_id" => $this->data['DepartmentsLocation']['location_id'], "department_id" => $this->data['DepartmentsLocation']['department_id']))); foreach($result as $row) { $this->delete($row['DepartmentsLocation']['id']); } return true; } } ?> The controllers are completely uninteresting. The problem: If I edit the name of a Location, all of the DepartmentsLocations that were linked to that Location are re-created with empty URLs. Since the models specify that unique is true, this also causes all of the newer rows to overwrite the older rows, which essentially destroys all of the URLs. I would like to know two things: Can I stop this? If so, how? And, on a less technical and more whiney note: Why does this even happen? It seems bizarre to me that editing a field through Cake should cause so much trouble, when I can easily go through phpMyAdmin, edit the Location name there, and get exactly the result I would expect. Why does CakePHP touch the HABTM data when I'm just editing a field on a row? It's not even a foreign key!

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• Monotone-increasing Version Number based on Mercurial Commits

  - by Isaac

  When I was using subversion for the code for an application, I could append a period and the result of svnversion to the version number to create a unique and monotone-increasing version number and also be guaranteed that any check-out of the same revision of the code would generate the same version number. In Mercurial, because revision numbers are not necessarily consistent across clones, the local revision number is not suitable. The hash is appropriately unique and consistent, but does not create a number that is monotone-increasing. How can I generate a suitable number to append to the version number based on the Mercurial repository commits?

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• Creating SQL Server index on a nvarchar column

  - by Jahan

  When I run this SQL statement: CREATE UNIQUE INDEX WordsIndex ON Words (Word ASC); I get the following exception message: The CREATE UNIQUE INDEX statement terminated because a duplicate key was found for the object name 'dbo.Words' and the index name 'WordsIndex'. The duplicate key value is (ass). The statement has been terminated. The 'Word' column has a datatype of nvarchar(100). There are two items in the 'Word' column that SQL Server interprets as the same: 'aß' and 'ass', which causes the indexing failure. Why would SQL Server interpret those two different words as the same word?

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