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Fix snapshot leak warning for some procedures

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The problem arises with the combination of CALL with output parameters
and doing a COMMIT inside the procedure.  When a CALL has output
parameters, the portal uses the strategy PORTAL_UTIL_SELECT instead of
PORTAL_MULTI_QUERY.  Using PORTAL_UTIL_SELECT causes the portal's
snapshot to be registered with the current resource
owner (portal->holdSnapshot); see
9ee1cf04ab6bcefe03a11837b53f29ca9dc24c7a for the reason.

Normally, PortalDrop() unregisters the snapshot.  If not, then
ResourceOwnerRelease() will print a warning about a snapshot leak on
transaction commit.  A transaction commit normally drops all
portals (PreCommit_Portals()), except the active portal.  So in case of
the active portal, we need to manually release the snapshot to avoid the
warning.

Reported-by: Prabhat Sahu <prabhat.sahu@enterprisedb.com>
Reviewed-by: Jonathan S. Katz <jkatz@postgresql.org>
This commit is contained in:
Peter Eisentraut 2018-08-23 15:13:48 +02:00
parent c5e235ff8a
commit 2657d4ea66
3 changed files with 67 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
src/backend/utils/mmgr/portalmem.c
View File

@ -689,13 +689,23 @@ PreCommit_Portals(bool isPrepare)
/*
* Do not touch active portals --- this can only happen in the case of
* a multi-transaction utility command, such as VACUUM.
* a multi-transaction utility command, such as VACUUM, or a commit in
* a procedure.
*
* Note however that any resource owner attached to such a portal is
* still going to go away, so don't leave a dangling pointer.
* still going to go away, so don't leave a dangling pointer. Also
* unregister any snapshots held by the portal, mainly to avoid
* snapshot leak warnings from ResourceOwnerRelease().
*/
if (portal->status == PORTAL_ACTIVE)
{
if (portal->holdSnapshot)
{
if (portal->resowner)
UnregisterSnapshotFromOwner(portal->holdSnapshot,
portal->resowner);
portal->holdSnapshot = NULL;
}
portal->resowner = NULL;
continue;
}

30
src/pl/plpgsql/src/expected/plpgsql_transaction.out
View File

@ -463,6 +463,36 @@ SELECT * FROM test2;
42
(1 row)
-- Test transaction in procedure with output parameters. This uses a
-- different portal strategy and different code paths in pquery.c.
CREATE PROCEDURE transaction_test10a(INOUT x int)
LANGUAGE plpgsql
AS $$
BEGIN
x := x + 1;
COMMIT;
END;
$$;
CALL transaction_test10a(10);
x
----
11
(1 row)
CREATE PROCEDURE transaction_test10b(INOUT x int)
LANGUAGE plpgsql
AS $$
BEGIN
x := x - 1;
ROLLBACK;
END;
$$;
CALL transaction_test10b(10);
x
---
9
(1 row)
DROP TABLE test1;
DROP TABLE test2;
DROP TABLE test3;

25
src/pl/plpgsql/src/sql/plpgsql_transaction.sql
View File

@ -387,6 +387,31 @@ $$;
SELECT * FROM test2;
-- Test transaction in procedure with output parameters. This uses a
-- different portal strategy and different code paths in pquery.c.
CREATE PROCEDURE transaction_test10a(INOUT x int)
LANGUAGE plpgsql
AS $$
BEGIN
x := x + 1;
COMMIT;
END;
$$;
CALL transaction_test10a(10);
CREATE PROCEDURE transaction_test10b(INOUT x int)
LANGUAGE plpgsql
AS $$
BEGIN
x := x - 1;
ROLLBACK;
END;
$$;
CALL transaction_test10b(10);
DROP TABLE test1;
DROP TABLE test2;
DROP TABLE test3;