Tom Lane escribió:
> Alvaro Herrera <[email protected]> writes:
> > Tom Lane escribió:
> >> Well, the first problem is that 8.4 is failing to duplicate the
> >> historical behavior.
>
> > Oh! That's easy.
>
> I don't think that testing rowMarks is the right thing at all here.
> That tells you whether it's a SELECT FOR UPDATE, but actually we
> want any cursor (and only cursors) to have a private snapshot.
The attached patch implements this. I intend to apply to 8.4 and HEAD
shortly.
--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.
Index: src/backend/commands/portalcmds.c
===================================================================
RCS file: /home/alvherre/Code/cvs/pgsql/src/backend/commands/portalcmds.c,v
retrieving revision 1.79
diff -c -p -r1.79 portalcmds.c
*** src/backend/commands/portalcmds.c 11 Jun 2009 14:48:56 -0000 1.79
--- src/backend/commands/portalcmds.c 1 Oct 2009 19:35:15 -0000
*************** PerformCursorOpen(PlannedStmt *stmt, Par
*** 47,52 ****
--- 47,53 ----
DeclareCursorStmt *cstmt = (DeclareCursorStmt *) stmt->utilityStmt;
Portal portal;
MemoryContext oldContext;
+ Snapshot snapshot;
if (cstmt == NULL || !IsA(cstmt, DeclareCursorStmt))
elog(ERROR, "PerformCursorOpen called for non-cursor query");
*************** PerformCursorOpen(PlannedStmt *stmt, Par
*** 119,127 ****
}
/*
* Start execution, inserting parameters if any.
*/
! PortalStart(portal, params, GetActiveSnapshot());
Assert(portal->strategy == PORTAL_ONE_SELECT);
--- 120,136 ----
}
/*
+ * Set up snapshot for portal. Note that we need a fresh, independent copy
+ * of the snapshot because we don't want it to be modified by future
+ * CommandCounterIncrement calls.
+ */
+ snapshot = RegisterCopiedSnapshot(GetActiveSnapshot(),
+ portal->resowner);
+
+ /*
* Start execution, inserting parameters if any.
*/
! PortalStart(portal, params, snapshot);
Assert(portal->strategy == PORTAL_ONE_SELECT);
Index: src/backend/utils/time/snapmgr.c
===================================================================
RCS file: /home/alvherre/Code/cvs/pgsql/src/backend/utils/time/snapmgr.c,v
retrieving revision 1.10
diff -c -p -r1.10 snapmgr.c
*** src/backend/utils/time/snapmgr.c 11 Jun 2009 14:49:06 -0000 1.10
--- src/backend/utils/time/snapmgr.c 1 Oct 2009 17:24:40 -0000
*************** RegisterSnapshotOnOwner(Snapshot snapsho
*** 385,390 ****
--- 385,403 ----
}
/*
+ * As above, but create a new, independeny copy of the snapshot.
+ */
+ Snapshot
+ RegisterCopiedSnapshot(Snapshot snapshot, ResourceOwner owner)
+ {
+ if (snapshot == InvalidSnapshot)
+ return InvalidSnapshot;
+
+ snapshot = CopySnapshot(snapshot);
+ return RegisterSnapshotOnOwner(snapshot, owner);
+ }
+
+ /*
* UnregisterSnapshot
*
* Decrement the reference count of a snapshot, remove the corresponding
Index: src/include/utils/snapmgr.h
===================================================================
RCS file: /home/alvherre/Code/cvs/pgsql/src/include/utils/snapmgr.h,v
retrieving revision 1.5
diff -c -p -r1.5 snapmgr.h
*** src/include/utils/snapmgr.h 11 Jun 2009 14:49:13 -0000 1.5
--- src/include/utils/snapmgr.h 1 Oct 2009 17:24:40 -0000
*************** extern bool ActiveSnapshotSet(void);
*** 36,41 ****
--- 36,42 ----
extern Snapshot RegisterSnapshot(Snapshot snapshot);
extern void UnregisterSnapshot(Snapshot snapshot);
extern Snapshot RegisterSnapshotOnOwner(Snapshot snapshot, ResourceOwner owner);
+ extern Snapshot RegisterCopiedSnapshot(Snapshot snapshot, ResourceOwner owner);
extern void UnregisterSnapshotFromOwner(Snapshot snapshot, ResourceOwner owner);
extern void AtSubCommit_Snapshot(int level);
--
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