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Fix multiple problems in postgres_fdw query cancellation logic.

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First, even if we cancel a query, we still have to roll back the
containing transaction; otherwise, the session will be left in a
failed transaction state.

Second, we need to support canceling queries whe aborting a
subtransaction as well as when aborting a toplevel transaction.

Etsuro Fujita, reviewed by Michael Paquier
This commit is contained in:
Robert Haas 2016-05-16 11:19:10 -04:00
parent b7a9347c11
commit 1b812afb0e
1 changed files with 25 additions and 3 deletions
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28
contrib/postgres_fdw/connection.c
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@ -677,8 +677,7 @@ pgfdw_xact_callback(XactEvent event, void *arg)
* using an asynchronous execution function, the command * using an asynchronous execution function, the command
* might not have yet completed. Check to see if a command * might not have yet completed. Check to see if a command
* is still being processed by the remote server, and if so, * is still being processed by the remote server, and if so,
* request cancellation of the command; if not, abort * request cancellation of the command.
* gracefully.
*/ */
if (PQtransactionStatus(entry->conn) == PQTRANS_ACTIVE) if (PQtransactionStatus(entry->conn) == PQTRANS_ACTIVE)
{ {
@ -694,7 +693,6 @@ pgfdw_xact_callback(XactEvent event, void *arg)
errbuf))); errbuf)));
PQfreeCancel(cancel); PQfreeCancel(cancel);
} }
break;
} }
/* If we're aborting, abort all remote transactions too */ /* If we're aborting, abort all remote transactions too */
@ -798,6 +796,30 @@ pgfdw_subxact_callback(SubXactEvent event, SubTransactionId mySubid,
{ {
/* Assume we might have lost track of prepared statements */ /* Assume we might have lost track of prepared statements */
entry->have_error = true; entry->have_error = true;
/*
* If a command has been submitted to the remote server by using an
* asynchronous execution function, the command might not have yet
* completed. Check to see if a command is still being processed by
* the remote server, and if so, request cancellation of the
* command.
*/
if (PQtransactionStatus(entry->conn) == PQTRANS_ACTIVE)
{
PGcancel *cancel;
char errbuf[256];
if ((cancel = PQgetCancel(entry->conn)))
{
if (!PQcancel(cancel, errbuf, sizeof(errbuf)))
ereport(WARNING,
(errcode(ERRCODE_CONNECTION_FAILURE),
errmsg("could not send cancel request: %s",
errbuf)));
PQfreeCancel(cancel);
}
}
/* Rollback all remote subtransactions during abort */ /* Rollback all remote subtransactions during abort */
snprintf(sql, sizeof(sql), snprintf(sql, sizeof(sql),
"ROLLBACK TO SAVEPOINT s%d; RELEASE SAVEPOINT s%d", "ROLLBACK TO SAVEPOINT s%d; RELEASE SAVEPOINT s%d",