I think I've found a reasonable fix for this.
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.
PreCommit_Portals() already contains some code that deals specially with
the active portal versus resource owners, so it seems reasonable to add
there.
I think this problem could theoretically apply to any
multiple-transaction utility command. For example, if we had a variant
of VACUUM that returned tuples, it would produce the same warning.
(This patch would fix that as well.)
--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
