transactions

问题 I have the below psql statements: Assumption :initial txid: a select txid_current(); ---------------------- a+1 begin; insert into tab( v1,v2); insert into tab (v3,v4); commit; select txid_current(); ---------------------- a+3 Why do I see the transaction ID as a+3 shouldn't it be a+2 ?? how does txid_current work? Is there any effective way where i could only return the current txid without the additional increment ? 回答1: Key points to understand: Everything is in a transaction. If you don't

问题 I have the below psql statements: Assumption :initial txid: a select txid_current(); ---------------------- a+1 begin; insert into tab( v1,v2); insert into tab (v3,v4); commit; select txid_current(); ---------------------- a+3 Why do I see the transaction ID as a+3 shouldn't it be a+2 ?? how does txid_current work? Is there any effective way where i could only return the current txid without the additional increment ? 回答1: Key points to understand: Everything is in a transaction. If you don't

问题 A quote from the EJB 3.1 specification: 13.6.1 Bean-Managed Transaction Demarcation The container must manage client invocations to an enterprise bean instance with bean-managed transaction demarcation as follows. When a client invokes a business method via one of the enterprise bean’s client views, the container suspends any transaction that may be associated with the client request. On the other hand, a transaction from a stand-alone client or another EJB is propagated into a bean using

问题 In postgres if I run the following statement update table set col = 1 where col = 2 In the default READ COMMITTED isolation level, from multiple concurrent sessions, am I guaranteed that: In a case of a single match only 1 thread will get a ROWCOUNT of 1 (meaning only one thread writes) In a case of a multi match that only 1 thread will get a ROWCOUNT > 0 (meaning only one thread writes the batch) 回答1: Your stated guarantees apply in this simple case, but not necessarily in slightly more

问题 Preliminary : I have an application which maintains a thread pool of about 100 threads. Each thread can last about 1-30 seconds before a new task replaces it. When a thread ends, that thread will almost always will result in inserting 1-3 records into a table, this table is used by all of the threads. Right now, no transactional support exists, but I am trying to add that now. Also, the table in question is InnoDB. So... Goal I want to implement a transaction for this. The rules for whether

问题 Whhen trying to test caching capabilities of Hibernate's (version 4) EHCache between transactions - it fails: Failed to retrieve PlatformTransactionManager for @Transactional test for test context . Test @RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration(classes = { ApplicationConfig.class, CachingConfig.class }, loader = AnnotationConfigContextLoader.class) @PersistenceContext @Transactional public class EHCacheTest extends AbstractTransactionalJUnit4SpringContextTests {

问题 Whhen trying to test caching capabilities of Hibernate's (version 4) EHCache between transactions - it fails: Failed to retrieve PlatformTransactionManager for @Transactional test for test context . Test @RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration(classes = { ApplicationConfig.class, CachingConfig.class }, loader = AnnotationConfigContextLoader.class) @PersistenceContext @Transactional public class EHCacheTest extends AbstractTransactionalJUnit4SpringContextTests {

问题 I'm using Spring 3.1.0.RELEASE, JUnit 4.8.1, and ultimately deploying my application to a JBoss 4.2 server (I know, I know). As part of setting up my unit test, I have this in my Spring test application context ... <bean id="transactionManager" class="org.springframework.transaction.jta.JtaTransactionManager"> <property name="userTransactionName"> <value>UserTransaction</value> </property> </bean> Of course, right now this fails because there is nothing bound to the JNDI name,

问题 Can you guys let me know the way of handling transactions in asp.net? i.e. I have a few queries (Present in different functions and called under various situations) that have to be executed as a whole. So, how should I go about it? Not sure of the syntax and the method/practice for writing the statements in .net (commit, rollback etc). Kindly let me know. Also, plz point me to some good articles if possible. Thanks!!! 回答1: I recommend using TransactionScope, because you can use it no mater

问题 I use PostgreSQL 9.2, and I do not use explicit locking anywhere, neither LOCK statement nor SELECT ... FOR UPDATE . However, recently I got ERROR: 40P01: deadlock detected . The query where deadlock was detected is wrapped in transaction block though. Anyway, how comes it? 回答1: You don't need any explicit LOCK to go into a deadlock. Here's a very simple demo from scratch with only INSERTs: create table a(i int primary key); create table b(i int primary key); Session #1 does: begin; insert