mirror of https://github.com/postgres/postgres
documentation warnings against setting it nonzero unless active use of prepared transactions is intended and a suitable transaction manager has been installed. This should help to prevent the type of scenario we've seen several times now where a prepared transaction is forgotten and eventually causes severe maintenance problems (or even anti-wraparound shutdown). The only real reason we had the default be nonzero in the first place was to support regression testing of the feature. To still be able to do that, tweak pg_regress to force a nonzero value during "make check". Since we cannot force a nonzero value in "make installcheck", add a variant regression test "expected" file that shows the results that will be obtained when max_prepared_transactions is zero. Also, extend the HINT messages for transaction wraparound warnings to mention the possibility that old prepared transactions are causing the problem. All per today's discussion.REL8_5_ALPHA1_BRANCH
Tom Lane
17 years ago
parent
bae8102f52
commit
8d4f2ecd41
@ -0,0 +1,223 @@ |
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-- |
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-- PREPARED TRANSACTIONS (two-phase commit) |
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-- |
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-- We can't readily test persistence of prepared xacts within the |
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-- regression script framework, unfortunately. Note that a crash |
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-- isn't really needed ... stopping and starting the postmaster would |
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-- be enough, but we can't even do that here. |
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-- create a simple table that we'll use in the tests |
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CREATE TABLE pxtest1 (foobar VARCHAR(10)); |
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INSERT INTO pxtest1 VALUES ('aaa'); |
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-- Test PREPARE TRANSACTION |
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BEGIN; |
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UPDATE pxtest1 SET foobar = 'bbb' WHERE foobar = 'aaa'; |
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SELECT * FROM pxtest1; |
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foobar |
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-------- |
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bbb |
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(1 row) |
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|
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PREPARE TRANSACTION 'foo1'; |
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ERROR: prepared transactions are disabled |
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HINT: Set max_prepared_transactions to a nonzero value. |
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SELECT * FROM pxtest1; |
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foobar |
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-------- |
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aaa |
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(1 row) |
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|
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-- Test pg_prepared_xacts system view |
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SELECT gid FROM pg_prepared_xacts; |
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gid |
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----- |
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(0 rows) |
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|
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-- Test ROLLBACK PREPARED |
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ROLLBACK PREPARED 'foo1'; |
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ERROR: prepared transaction with identifier "foo1" does not exist |
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SELECT * FROM pxtest1; |
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foobar |
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-------- |
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aaa |
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(1 row) |
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|
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SELECT gid FROM pg_prepared_xacts; |
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gid |
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----- |
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(0 rows) |
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|
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-- Test COMMIT PREPARED |
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BEGIN; |
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INSERT INTO pxtest1 VALUES ('ddd'); |
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SELECT * FROM pxtest1; |
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foobar |
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-------- |
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aaa |
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ddd |
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(2 rows) |
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|
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PREPARE TRANSACTION 'foo2'; |
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ERROR: prepared transactions are disabled |
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HINT: Set max_prepared_transactions to a nonzero value. |
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SELECT * FROM pxtest1; |
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foobar |
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-------- |
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aaa |
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(1 row) |
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|
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COMMIT PREPARED 'foo2'; |
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ERROR: prepared transaction with identifier "foo2" does not exist |
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SELECT * FROM pxtest1; |
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foobar |
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-------- |
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aaa |
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(1 row) |
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|
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-- Test duplicate gids |
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BEGIN; |
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UPDATE pxtest1 SET foobar = 'eee' WHERE foobar = 'ddd'; |
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SELECT * FROM pxtest1; |
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foobar |
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-------- |
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aaa |
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(1 row) |
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|
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PREPARE TRANSACTION 'foo3'; |
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ERROR: prepared transactions are disabled |
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HINT: Set max_prepared_transactions to a nonzero value. |
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SELECT gid FROM pg_prepared_xacts; |
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gid |
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----- |
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(0 rows) |
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|
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BEGIN; |
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INSERT INTO pxtest1 VALUES ('fff'); |
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SELECT * FROM pxtest1; |
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foobar |
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-------- |
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aaa |
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fff |
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(2 rows) |
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|
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-- This should fail, because the gid foo3 is already in use |
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PREPARE TRANSACTION 'foo3'; |
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ERROR: prepared transactions are disabled |
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HINT: Set max_prepared_transactions to a nonzero value. |
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SELECT * FROM pxtest1; |
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foobar |
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-------- |
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aaa |
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(1 row) |
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|
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ROLLBACK PREPARED 'foo3'; |
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ERROR: prepared transaction with identifier "foo3" does not exist |
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SELECT * FROM pxtest1; |
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foobar |
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-------- |
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aaa |
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(1 row) |
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|
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-- Clean up |
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DROP TABLE pxtest1; |
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-- Test subtransactions |
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BEGIN; |
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CREATE TABLE pxtest2 (a int); |
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INSERT INTO pxtest2 VALUES (1); |
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SAVEPOINT a; |
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INSERT INTO pxtest2 VALUES (2); |
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ROLLBACK TO a; |
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SAVEPOINT b; |
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INSERT INTO pxtest2 VALUES (3); |
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PREPARE TRANSACTION 'regress-one'; |
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ERROR: prepared transactions are disabled |
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HINT: Set max_prepared_transactions to a nonzero value. |
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CREATE TABLE pxtest3(fff int); |
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-- Test shared invalidation |
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BEGIN; |
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DROP TABLE pxtest3; |
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CREATE TABLE pxtest4 (a int); |
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INSERT INTO pxtest4 VALUES (1); |
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INSERT INTO pxtest4 VALUES (2); |
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DECLARE foo CURSOR FOR SELECT * FROM pxtest4; |
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-- Fetch 1 tuple, keeping the cursor open |
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FETCH 1 FROM foo; |
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a |
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--- |
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1 |
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(1 row) |
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|
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PREPARE TRANSACTION 'regress-two'; |
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ERROR: prepared transactions are disabled |
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HINT: Set max_prepared_transactions to a nonzero value. |
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-- No such cursor |
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FETCH 1 FROM foo; |
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ERROR: cursor "foo" does not exist |
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-- Table doesn't exist, the creation hasn't been committed yet |
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SELECT * FROM pxtest2; |
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ERROR: relation "pxtest2" does not exist |
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LINE 1: SELECT * FROM pxtest2; |
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^ |
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-- There should be two prepared transactions |
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SELECT gid FROM pg_prepared_xacts; |
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gid |
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----- |
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(0 rows) |
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|
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-- pxtest3 should be locked because of the pending DROP |
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set statement_timeout to 2000; |
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SELECT * FROM pxtest3; |
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fff |
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----- |
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(0 rows) |
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|
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reset statement_timeout; |
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-- Disconnect, we will continue testing in a different backend |
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\c - |
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-- There should still be two prepared transactions |
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SELECT gid FROM pg_prepared_xacts; |
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gid |
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----- |
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(0 rows) |
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|
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-- pxtest3 should still be locked because of the pending DROP |
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set statement_timeout to 2000; |
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SELECT * FROM pxtest3; |
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fff |
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----- |
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(0 rows) |
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|
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reset statement_timeout; |
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-- Commit table creation |
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COMMIT PREPARED 'regress-one'; |
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ERROR: prepared transaction with identifier "regress-one" does not exist |
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\d pxtest2 |
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SELECT * FROM pxtest2; |
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ERROR: relation "pxtest2" does not exist |
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LINE 1: SELECT * FROM pxtest2; |
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^ |
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-- There should be one prepared transaction |
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SELECT gid FROM pg_prepared_xacts; |
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gid |
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----- |
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(0 rows) |
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|
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-- Commit table drop |
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COMMIT PREPARED 'regress-two'; |
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ERROR: prepared transaction with identifier "regress-two" does not exist |
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SELECT * FROM pxtest3; |
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fff |
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----- |
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(0 rows) |
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|
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-- There should be no prepared transactions |
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SELECT gid FROM pg_prepared_xacts; |
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gid |
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----- |
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(0 rows) |
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|
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-- Clean up |
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DROP TABLE pxtest2; |
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ERROR: table "pxtest2" does not exist |
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DROP TABLE pxtest3; -- will still be there if prepared xacts are disabled |
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DROP TABLE pxtest4; |
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ERROR: table "pxtest4" does not exist |
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