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authorTom Lane2016-09-22 15:34:45 +0000
committerTom Lane2016-09-22 15:34:45 +0000
commit0183df5dc000fccf121c1a54504044578e43ec8e (patch)
tree16f5f3d6eb6b80ab3a5cfae119e809441e3e4bba
parentee33250f759108c0be163452c10677af0a99ef9e (diff)
Be sure to rewind the tuplestore read pointer in non-leader CTEScan nodes.
ExecInitCteScan supposed that it didn't have to do anything to the extra tuplestore read pointer it gets from tuplestore_alloc_read_pointer. However, it needs this read pointer to be positioned at the start of the tuplestore, while tuplestore_alloc_read_pointer is actually defined as cloning the current position of read pointer 0. In normal situations that accidentally works because we initialize the whole plan tree at once, before anything gets read. But it fails in an EvalPlanQual recheck, as illustrated in bug #14328 from Dima Pavlov. To fix, just forcibly rewind the pointer after tuplestore_alloc_read_pointer. The cost of doing so is negligible unless the tuplestore is already in TSS_READFILE state, which wouldn't happen in normal cases. We could consider altering tuplestore's API to make that case cheaper, but that would make for a more invasive back-patch and it doesn't seem worth it. This has been broken probably for as long as we've had CTEs, so back-patch to all supported branches. Discussion: <[email protected]>
-rw-r--r--src/backend/executor/nodeCtescan.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/src/backend/executor/nodeCtescan.c b/src/backend/executor/nodeCtescan.c
index a763905df11..b9c58096313 100644
--- a/src/backend/executor/nodeCtescan.c
+++ b/src/backend/executor/nodeCtescan.c
@@ -224,9 +224,13 @@ ExecInitCteScan(CteScan *node, EState *estate, int eflags)
{
/* Not the leader */
Assert(IsA(scanstate->leader, CteScanState));
+ /* Create my own read pointer, and ensure it is at start */
scanstate->readptr =
tuplestore_alloc_read_pointer(scanstate->leader->cte_table,
scanstate->eflags);
+ tuplestore_select_read_pointer(scanstate->leader->cte_table,
+ scanstate->readptr);
+ tuplestore_rescan(scanstate->leader->cte_table);
}
/*