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Commit04e5025

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Fix failure to set ActiveSnapshot while rewinding a cursor.
ActiveSnapshot needs to be set when we call ExecutorRewind because someplan node types may execute user-defined functions during their ReScancalls (nodeLimit.c does so, at least). The wisdom of that is somewhatdebatable, perhaps, but for now the simplest fix is to make sure therequired context is valid. Failure to do this typically led to anull-pointer-dereference core dump, though it's possible that in morecomplex cases a function could be executed with the wrong snapshotleading to very subtle misbehavior.Per report from Leif Jensen. It's been broken for a long time, soback-patch to all active branches.
1 parente2ce9aa commit04e5025

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3 files changed

+47
-2
lines changed

3 files changed

+47
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lines changed

‎src/backend/tcop/pquery.c

Lines changed: 12 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1661,6 +1661,9 @@ DoPortalRunFetch(Portal portal,
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staticvoid
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DoPortalRewind(Portalportal)
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{
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QueryDesc*queryDesc;
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/* Rewind holdStore, if we have one */
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if (portal->holdStore)
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{
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MemoryContextoldcontext;
@@ -1669,8 +1672,15 @@ DoPortalRewind(Portal portal)
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tuplestore_rescan(portal->holdStore);
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MemoryContextSwitchTo(oldcontext);
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}
1672-
if (PortalGetQueryDesc(portal))
1673-
ExecutorRewind(PortalGetQueryDesc(portal));
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/* Rewind executor, if active */
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queryDesc=PortalGetQueryDesc(portal);
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if (queryDesc)
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{
1680+
PushActiveSnapshot(queryDesc->snapshot);
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ExecutorRewind(queryDesc);
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PopActiveSnapshot();
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}
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portal->atStart= true;
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portal->atEnd= false;

‎src/test/regress/expected/portals.out

Lines changed: 24 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1261,3 +1261,27 @@ FETCH ALL FROM c1;
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COMMIT;
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DROP TABLE cursor;
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-- Check rewinding a cursor containing a stable function in LIMIT,
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-- per bug report in 8336843.9833.1399385291498.JavaMail.root@quick
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begin;
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create function nochange(int) returns int
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as 'select $1 limit 1' language sql stable;
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declare c cursor for select * from int8_tbl limit nochange(3);
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fetch all from c;
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q1 | q2
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------------------+------------------
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123 | 456
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123 | 4567890123456789
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4567890123456789 | 123
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(3 rows)
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move backward all in c;
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fetch all from c;
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q1 | q2
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------------------+------------------
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123 | 456
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123 | 4567890123456789
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4567890123456789 | 123
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(3 rows)
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rollback;

‎src/test/regress/sql/portals.sql

Lines changed: 11 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -473,3 +473,14 @@ UPDATE cursor SET a = 2;
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FETCH ALLFROM c1;
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COMMIT;
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DROPTABLE cursor;
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-- Check rewinding a cursor containing a stable function in LIMIT,
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-- per bug report in 8336843.9833.1399385291498.JavaMail.root@quick
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begin;
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createfunctionnochange(int) returnsint
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as'select $1 limit 1' language sql stable;
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declare c cursor forselect*from int8_tbllimit nochange(3);
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fetch allfrom c;
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move backward allin c;
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fetch allfrom c;
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rollback;

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