bug with select for update
От | Barry Lind |
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Тема | bug with select for update |
Дата | |
Msg-id | 3C676721.30704@xythos.com обсуждение исходный текст |
Ответы |
Re: bug with select for update
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Список | pgsql-hackers |
I have just isolated a bug in doing a 'select for update'. I have included a test case below that reproduces the problem on a 7.2 database. The bug is as follows: after issuing a select for update that blocks on a record being locked by a second process, when that second process commits, the first process begins using 100% of the cpu and never completes. The test case is as follows: drop table test1; drop table test2; create table test1 (cola int); create unique index test1_u1 on test1(cola); create table test2 (cola int); create unique index test2_u1 on test2(cola); insert into test1 values (1); insert into test2 values (1); Then in one psql session issue the following: begin; UPDATE TEST1 SET COLA = 1 WHERE COLA = 1; Then in a second psql issue the following: begin; SELECT T1.COLA FROM TEST1 T1, TEST2 T2 WHERE T1.COLA = T2.COLA AND T2.COLA = 1 FOR UPDATE; Now go back to the first psql and issue the following: commit; Now you will see the cpu usage spike up to 100% for the second process and it will never return. Running analyze on these newly created tables will cause the indexes not to be used and will result in the select working correctly. However in my real code the indexes are necessary and thus that isn't a workaround for me. thanks, --Barry
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