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Commit7cabb20

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Fix COMMIT/ROLLBACK AND CHAIN in the presence of subtransactions.
In older branches, COMMIT/ROLLBACK AND CHAIN failed to propagatethe current transaction's properties to the new transaction ifthere was any open subtransaction (unreleased savepoint).Instead, some previous transaction's properties would be restored.This is because the "if (s->chain)" check in CommitTransactionCommandexamined the wrong instance of the "chain" flag and falselyconcluded that it didn't need to save transaction properties.Our regression tests would have noticed this, except they usedidentical transaction properties for multiple tests in a row,so that the faulty behavior was not distinguishable from correctbehavior.Commit12d768e fixed the problem in v15 and later, but only ratheraccidentally, because I removed the "if (s->chain)" test to avoid acompiler warning, while not realizing that the warning was flagging areal bug.In v14 and before, remove the if-test and save transaction propertiesunconditionally; just as in the newer branches, that's not expensiveenough to justify thinking harder.Add the comment and extra regression test to v15 and later toforestall any future recurrence, but there's no live bug in thosebranches.Patch by me, per bug #18118 from Liu Xiang. Back-patch to v12 wherethe AND CHAIN feature was added.Discussion:https://postgr.es/m/18118-4b72fcbb903aace6@postgresql.org
1 parentc50ad79 commit7cabb20

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3 files changed

+53
-2
lines changed

3 files changed

+53
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lines changed

‎src/backend/access/transam/xact.c

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Original file line numberDiff line numberDiff line change
@@ -2913,8 +2913,8 @@ CommitTransactionCommand(void)
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{
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TransactionStates=CurrentTransactionState;
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if (s->chain)
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SaveTransactionCharacteristics();
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/* Must save in case we need to restore below */
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SaveTransactionCharacteristics();
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switch (s->blockState)
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{

‎src/test/regress/expected/transactions.out

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Original file line numberDiff line numberDiff line change
@@ -814,6 +814,46 @@ SHOW transaction_deferrable;
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on
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(1 row)
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COMMIT;
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START TRANSACTION ISOLATION LEVEL READ COMMITTED, READ WRITE, DEFERRABLE;
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SHOW transaction_isolation;
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transaction_isolation
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-----------------------
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read committed
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(1 row)
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SHOW transaction_read_only;
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transaction_read_only
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-----------------------
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off
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(1 row)
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SHOW transaction_deferrable;
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transaction_deferrable
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------------------------
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on
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(1 row)
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SAVEPOINT x;
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COMMIT AND CHAIN; -- TBLOCK_SUBCOMMIT
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SHOW transaction_isolation;
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transaction_isolation
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-----------------------
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read committed
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(1 row)
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SHOW transaction_read_only;
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transaction_read_only
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-----------------------
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off
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(1 row)
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SHOW transaction_deferrable;
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transaction_deferrable
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------------------------
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on
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(1 row)
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COMMIT;
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-- different mix of options just for fun
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START TRANSACTION ISOLATION LEVEL SERIALIZABLE, READ WRITE, NOT DEFERRABLE;

‎src/test/regress/sql/transactions.sql

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Original file line numberDiff line numberDiff line change
@@ -469,6 +469,17 @@ SHOW transaction_read_only;
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SHOW transaction_deferrable;
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COMMIT;
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START TRANSACTION ISOLATION LEVEL READ COMMITTED, READ WRITE, DEFERRABLE;
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SHOW transaction_isolation;
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SHOW transaction_read_only;
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SHOW transaction_deferrable;
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SAVEPOINT x;
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COMMITAND CHAIN;-- TBLOCK_SUBCOMMIT
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SHOW transaction_isolation;
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SHOW transaction_read_only;
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SHOW transaction_deferrable;
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COMMIT;
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-- different mix of options just for fun
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START TRANSACTION ISOLATION LEVEL SERIALIZABLE, READ WRITE, NOT DEFERRABLE;
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SHOW transaction_isolation;

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