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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
9ee1cf04ab 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 cbdca00bef
commit 7a3b7bbfde
3 changed files with 67 additions and 2 deletions
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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;
}