From 1b812afb0eafe125b820cc3b95e7ca03821aa675 Mon Sep 17 00:00:00 2001 From: Robert Haas Date: Mon, 16 May 2016 11:19:10 -0400 Subject: [PATCH] Fix multiple problems in postgres_fdw query cancellation logic. 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 --- contrib/postgres_fdw/connection.c | 28 +++++++++++++++++++++++++--- 1 file changed, 25 insertions(+), 3 deletions(-) diff --git a/contrib/postgres_fdw/connection.c b/contrib/postgres_fdw/connection.c index 16ef38fff7..43c7fc9e08 100644 --- a/contrib/postgres_fdw/connection.c +++ b/contrib/postgres_fdw/connection.c @@ -677,8 +677,7 @@ pgfdw_xact_callback(XactEvent event, void *arg) * 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 not, abort - * gracefully. + * request cancellation of the command. */ if (PQtransactionStatus(entry->conn) == PQTRANS_ACTIVE) { @@ -694,7 +693,6 @@ pgfdw_xact_callback(XactEvent event, void *arg) errbuf))); PQfreeCancel(cancel); } - break; } /* 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 */ 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 */ snprintf(sql, sizeof(sql), "ROLLBACK TO SAVEPOINT s%d; RELEASE SAVEPOINT s%d",