From 1b812afb0eafe125b820cc3b95e7ca03821aa675 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
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 16ef38fff78..43c7fc9e080 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",
--
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