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Only install a portal's ResourceOwner if it actually has one.

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In most scenarios a portal without a ResourceOwner is dead and not subject
to any further execution, but a portal for a cursor WITH HOLD remains in
existence with no ResourceOwner after the creating transaction is over.
In this situation, if we attempt to "execute" the portal directly to fetch
data from it, we were setting CurrentResourceOwner to NULL, leading to a
segfault if the datatype output code did anything that required a resource
owner (such as trying to fetch system catalog entries that weren't already
cached).  The case appears to be impossible to provoke with stock libpq,
but psqlODBC at least is able to cause it when working with held cursors.

Simplest fix is to just skip the assignment to CurrentResourceOwner, so
that any resources used by the data output operations will be managed by
the transaction-level resource owner instead.  For consistency I changed
all the places that install a portal's resowner as current, even though
some of them are probably not reachable with a held cursor's portal.

Per report from Joshua Berry (with thanks to Hiroshi Inoue for developing
a self-contained test case).  Back-patch to all supported versions.
This commit is contained in:
Tom Lane 2013-06-13 13:11:29 -04:00
parent 66008564f8
commit 629b3e96dd
2 changed files with 10 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
src/backend/commands/portalcmds.c
View File

@ -274,7 +274,8 @@ PortalCleanup(Portal portal)
saveResourceOwner = CurrentResourceOwner;
PG_TRY();
{
CurrentResourceOwner = portal->resowner;
if (portal->resowner)
CurrentResourceOwner = portal->resowner;
ExecutorFinish(queryDesc);
ExecutorEnd(queryDesc);
FreeQueryDesc(queryDesc);
@ -349,7 +350,8 @@ PersistHoldablePortal(Portal portal)
PG_TRY();
{
ActivePortal = portal;
CurrentResourceOwner = portal->resowner;
if (portal->resowner)
CurrentResourceOwner = portal->resowner;
PortalContext = PortalGetHeapMemory(portal);
MemoryContextSwitchTo(PortalContext);

9
src/backend/tcop/pquery.c
View File

@ -478,7 +478,8 @@ PortalStart(Portal portal, ParamListInfo params,
PG_TRY();
{
ActivePortal = portal;
CurrentResourceOwner = portal->resowner;
if (portal->resowner)
CurrentResourceOwner = portal->resowner;
PortalContext = PortalGetHeapMemory(portal);
oldContext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
@ -762,7 +763,8 @@ PortalRun(Portal portal, long count, bool isTopLevel,
PG_TRY();
{
ActivePortal = portal;
CurrentResourceOwner = portal->resowner;
if (portal->resowner)
CurrentResourceOwner = portal->resowner;
PortalContext = PortalGetHeapMemory(portal);
MemoryContextSwitchTo(PortalContext);
@ -1411,7 +1413,8 @@ PortalRunFetch(Portal portal,
PG_TRY();
{
ActivePortal = portal;
CurrentResourceOwner = portal->resowner;
if (portal->resowner)
CurrentResourceOwner = portal->resowner;
PortalContext = PortalGetHeapMemory(portal);
oldContext = MemoryContextSwitchTo(PortalContext);