From ae35363dced47a99178b4a4129e3ea1f990b829c Mon Sep 17 00:00:00 2001 From: Alvaro Herrera Date: Fri, 2 Oct 2009 17:58:21 +0000 Subject: Ensure that a cursor has an immutable snapshot throughout its lifespan. The old coding was using a regular snapshot, referenced elsewhere, that was subject to having its command counter updated. Fix by creating a private copy of the snapshot exclusively for the cursor. Backpatch to 8.4, which is when the bug was introduced during the snapshot management rewrite. --- src/backend/commands/portalcmds.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) (limited to 'src/backend/commands/portalcmds.c') diff --git a/src/backend/commands/portalcmds.c b/src/backend/commands/portalcmds.c index 17192341739..d31fde65b6b 100644 --- a/src/backend/commands/portalcmds.c +++ b/src/backend/commands/portalcmds.c @@ -14,7 +14,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/commands/portalcmds.c,v 1.79 2009/06/11 14:48:56 momjian Exp $ + * $PostgreSQL: pgsql/src/backend/commands/portalcmds.c,v 1.79.2.1 2009/10/02 17:58:21 alvherre Exp $ * *------------------------------------------------------------------------- */ @@ -47,6 +47,7 @@ PerformCursorOpen(PlannedStmt *stmt, ParamListInfo params, 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"); @@ -118,10 +119,18 @@ PerformCursorOpen(PlannedStmt *stmt, ParamListInfo params, portal->cursorOptions |= CURSOR_OPT_NO_SCROLL; } + /* + * 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. We do not register it, because + * portalmem.c will take care of that internally. + */ + snapshot = CopySnapshot(GetActiveSnapshot()); + /* * Start execution, inserting parameters if any. */ - PortalStart(portal, params, GetActiveSnapshot()); + PortalStart(portal, params, snapshot); Assert(portal->strategy == PORTAL_ONE_SELECT); -- cgit v1.2.3