From e8854c876927b32e21f485337dd2335f4bfebd32 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Mon, 8 Apr 2019 15:18:19 +0300 Subject: [PATCH 1/4] Fix confusion on different kinds of slots in IndexOnlyScans. We used the same slot, to store a tuple from the index, and to store a tuple from the table. That's not OK. It worked with the heap, because heapam_getnextslot() stores a HeapTuple to the slot, and doesn't care how large the tts_values/nulls arrays are. But when I played with a toy table AM implementation that used a virtual tuple, it caused memory overruns. --- src/backend/executor/nodeIndexonlyscan.c | 16 +++++++++++++--- src/include/nodes/execnodes.h | 1 + 2 files changed, 14 insertions(+), 3 deletions(-) diff --git a/src/backend/executor/nodeIndexonlyscan.c b/src/backend/executor/nodeIndexonlyscan.c index 7711728495c..5833d683b38 100644 --- a/src/backend/executor/nodeIndexonlyscan.c +++ b/src/backend/executor/nodeIndexonlyscan.c @@ -166,10 +166,10 @@ IndexOnlyNext(IndexOnlyScanState *node) * Rats, we have to visit the heap to check visibility. */ InstrCountTuples2(node, 1); - if (!index_fetch_heap(scandesc, slot)) + if (!index_fetch_heap(scandesc, node->ioss_TableSlot)) continue; /* no visible tuple, try next index entry */ - ExecClearTuple(slot); + ExecClearTuple(node->ioss_TableSlot); /* * Only MVCC snapshots are supported here, so there should be no @@ -528,7 +528,17 @@ ExecInitIndexOnlyScan(IndexOnlyScan *node, EState *estate, int eflags) */ tupDesc = ExecTypeFromTL(node->indextlist); ExecInitScanTupleSlot(estate, &indexstate->ss, tupDesc, - table_slot_callbacks(currentRelation)); + &TTSOpsVirtual); + + /* + * We need another slot, in a format that's suitable for the table AM, + * for when we need to fetch a tuple from the table for rechecking + * visibility. + */ + indexstate->ioss_TableSlot = + ExecAllocTableSlot(&estate->es_tupleTable, + RelationGetDescr(currentRelation), + table_slot_callbacks(currentRelation)); /* * Initialize result type and projection info. The node's targetlist will diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h index a5e4b7ef2e0..108dee61e24 100644 --- a/src/include/nodes/execnodes.h +++ b/src/include/nodes/execnodes.h @@ -1424,6 +1424,7 @@ typedef struct IndexOnlyScanState struct IndexScanDescData *ioss_ScanDesc; Buffer ioss_VMBuffer; Size ioss_PscanLen; + TupleTableSlot *ioss_TableSlot; } IndexOnlyScanState; /* ---------------- -- 2.20.1