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

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.

diff --git a/src/backend/commands/portalcmds.c b/src/backend/commands/portalcmds.c
index 9c4d02627a155543a2e198643e9acc48544c5869..5c3f42cb71681b15072b77f2f57ddd599d8c00f7 100644 (file)
--- a/src/backend/commands/portalcmds.c
+++ b/src/backend/commands/portalcmds.c
@@ -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);

diff --git a/src/backend/tcop/pquery.c b/src/backend/tcop/pquery.c
index f8989f7a9e9725288bf8f79111455a1ad9e7f28e..f400e935d13e8bab95f946c3b1b78a74df25d8db 100644 (file)
--- a/src/backend/tcop/pquery.c
+++ b/src/backend/tcop/pquery.c
@@ -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);