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[2009-10-24 12:47 UTC] ben dot pineau at gmail dot com
Description:
------------
When prepar()ing a statement in a separate function, pdo_pgsql behaves as if we hadn't rollbacked and started a new transaction.
But no such problem when either :
- we use another pdo driver (tested with sqlite)
- prepare() call is inlined in the same code block as beginTransaction (rather than in a distinct function)
- the function contains a straigth "query()" instead of prepare() + execute()
Reproduced with both php-5.2.6 and php-5.2.11, PostgreSQL 8.3.8.
Reproduce code:
---------------
/*
* CREATE TABLE test (a SERIAL PRIMARY KEY);
* INSERT INTO test VALUES (1);
*/
$cnx = new PDO('pgsql:dbname=testbase;host=localhost', 'postgres','');
$cnx->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$sql = "INSERT INTO test (a) VALUES (1)";
function prepare_and_exec_query(&$pdo, $sql)
{
$stmt = $pdo->prepare($sql);
$stmt->execute();
}
for ($i = 0; $i < 3; $i++) {
try {
$cnx->beginTransaction();
prepare_and_exec_query($cnx, $sql);
$cnx->commit();
} catch (Exception $e) {
echo "Error: " . $e->getMessage() . "\n";
if (true === $cnx->rollback()) echo "rollbacked ok\n";
}
}
Expected result:
----------------
Error: SQLSTATE[23505]: Unique violation: 7 ERROR: duplicate key value violates unique constraint "test_pkey"
rollbacked ok
Error: SQLSTATE[23505]: Unique violation: 7 ERROR: duplicate key value violates unique constraint "test_pkey"
rollbacked ok
Error: SQLSTATE[23505]: Unique violation: 7 ERROR: duplicate key value violates unique constraint "test_pkey"
rollbacked ok
Actual result:
--------------
Error: SQLSTATE[23505]: Unique violation: 7 ERROR: duplicate key value violates unique constraint "test_pkey"
rollbacked ok
Error: SQLSTATE[25P02]: In failed sql transaction: 7 ERROR: current transaction is aborted, commands ignored until end of transaction block
rollbacked ok
Error: SQLSTATE[25P02]: In failed sql transaction: 7 ERROR: current transaction is aborted, commands ignored until end of transaction block
rollbacked ok
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Last updated: Tue Mar 04 06:01:27 2025 UTC |
Look at the PostgreSQL logs above (running the provided test case with log_statement='all' and log_min_messages='INFO'), keeping in mind that: - PostgreSQL automatically abort transactions when something fails. - PostgreSQL does maintains prepared statements outside transaction context. Prepared statements survive a rollback/abort, and last for the duration of the current database session. - It seems that when executed in another function/context than PDO::beginTransaction, PDO tries to DEALLOCATE right after the first transaction failure (vs. after the next BEGIN statement when in same context). Therefore we have the following flow: BEGIN; -- PDO successfully prepare the statement PREPARE prep_statement_1 AS ...; -- We execute a bogus statement that cause pg to automatically -- abort the current transaction. PDO raise a proper exception EXECUTE prep_statement_1; -- This fails because we're in aborted transaction; -- The prepared statement is thus left allocated. DEALLOCATE prep_statement_1; ROLLBACK; -- And then we loop with BEGIN; -- This prep statement already exists (PDO failed to clean it) -- so this fails and pg automatically abort this new transaction. PREPARE prep_statement_1 AS ...; -- Given the above failure, PDO tries again to clean up the -- prepared stmt which will fail again. -- Hence PDO raising a "current transaction is aborted" exception. DEALLOCATE prep_statement_1; ROLLBACK; Surprisingly, when we call prepare() inline like this: try { $cnx->beginTransaction(); $stmt = $cnx->prepare($sql); $stmt->execute(); instead of that : function qexec(&$pdo, $sql) { $stmt = $pdo->prepare($sql); $stmt->execute(); } try { $cnx->beginTransaction(); qexec($cnx, $sql); we do get a different (and preferable) behaviour: BEGIN -> PREPARE -> EXECUTE -> ROLLBACK -> BEGIN -> DEALLOCATE -> PREPARE -> EXECUTE -> ROLLBACK -> BEGIN -> DEALLOCATE -> PREPARE -> EXECUTE -> ROLLBACK -> ... vs. BEGIN -> PREPARE -> EXECUTE -> DEALLOCATE -> ROLLBACK -> BEGIN -> PREPARE (-> EXECUTE) -> DEALLOCATE -> ROLLBACK -> BEGIN -> PREPARE (-> EXECUTE) -> DEALLOCATE -> ROLLBACK -> ... Granted, preparing the same exact statement in loop (rather than once then using varying parameters) is dumb, but... PostgreSQL logs from the provided test case: Oct 24 15:29:15 dev postgres[26864]: [5-1] LOG: statement: BEGIN Oct 24 15:29:15 dev postgres[26864]: [6-1] LOG: execute pdo_pgsql_stmt_01ef7698: INSERT INTO test (a) VALUES (1) Oct 24 15:29:15 dev postgres[26864]: [7-1] ERROR: duplicate key value violates unique constraint "test_pkey" Oct 24 15:29:15 dev postgres[26864]: [7-2] STATEMENT: INSERT INTO test (a) VALUES (1) Oct 24 15:29:15 dev postgres[26864]: [8-1] LOG: statement: DEALLOCATE pdo_pgsql_stmt_01ef7698 Oct 24 15:29:15 dev postgres[26864]: [9-1] ERROR: current transaction is aborted, commands ignored until end of transaction block Oct 24 15:29:15 dev postgres[26864]: [9-2] STATEMENT: DEALLOCATE pdo_pgsql_stmt_01ef7698 Oct 24 15:29:15 dev postgres[26864]: [10-1] LOG: statement: ROLLBACK Oct 24 15:29:15 dev postgres[26864]: [11-1] LOG: statement: BEGIN Oct 24 15:29:15 dev postgres[26864]: [12-1] ERROR: prepared statement "pdo_pgsql_stmt_01ef7698" already exists Oct 24 15:29:15 dev postgres[26864]: [12-2] STATEMENT: INSERT INTO test (a) VALUES (1) Oct 24 15:29:15 dev postgres[26864]: [13-1] LOG: statement: DEALLOCATE pdo_pgsql_stmt_01ef7698 Oct 24 15:29:15 dev postgres[26864]: [14-1] ERROR: current transaction is aborted, commands ignored until end of transaction block Oct 24 15:29:15 dev postgres[26864]: [14-2] STATEMENT: DEALLOCATE pdo_pgsql_stmt_01ef7698 Oct 24 15:29:15 dev postgres[26864]: [15-1] ERROR: current transaction is aborted, commands ignored until end of transaction block Oct 24 15:29:15 dev postgres[26864]: [15-2] STATEMENT: INSERT INTO test (a) VALUES (1) Oct 24 15:29:15 dev postgres[26864]: [16-1] LOG: statement: ROLLBACK Oct 24 15:29:15 dev postgres[26864]: [17-1] LOG: statement: BEGIN Oct 24 15:29:15 dev postgres[26864]: [18-1] ERROR: prepared statement "pdo_pgsql_stmt_01ef7698" already exists Oct 24 15:29:15 dev postgres[26864]: [18-2] STATEMENT: INSERT INTO test (a) VALUES (1) Oct 24 15:29:15 dev postgres[26864]: [19-1] LOG: statement: DEALLOCATE pdo_pgsql_stmt_01ef7698 Oct 24 15:29:15 dev postgres[26864]: [20-1] ERROR: current transaction is aborted, commands ignored until end of transaction block Oct 24 15:29:15 dev postgres[26864]: [20-2] STATEMENT: DEALLOCATE pdo_pgsql_stmt_01ef7698 Oct 24 15:29:15 dev postgres[26864]: [21-1] ERROR: current transaction is aborted, commands ignored until end of transaction block Oct 24 15:29:15 dev postgres[26864]: [21-2] STATEMENT: INSERT INTO test (a) VALUES (1) Oct 24 15:29:15 dev postgres[26864]: [22-1] LOG: statement: ROLLBACK