Add missing EPQ recheck for TID Scan

The EvalPlanQual recheck for TID Scan wasn't rechecking the TID qual
still passed after following update chains.  This could result in tuples
being updated or deleted by plans using TID Scans where the ctid of the
new (updated) tuple no longer matches the clause of the scan.  This isn't
desired behavior, and isn't consistent with what would happen if the
chosen plan had used an Index or Seq Scan, and that could lead to hard to
predict behavior for scans that contain TID quals and other quals as the
planner has freedom to choose TID or some other scan method for such
queries, and the chosen plan could change at any moment.

Here we fix this by properly implementing the recheck function for TID
Scans.

Backpatch to 13, oldest supported version

Reported-by: Sophie Alpert <pg@sophiebits.com>
Author: Sophie Alpert <pg@sophiebits.com>
Author: David Rowley <dgrowleyml@gmail.com>
Reviewed-by: David Rowley <dgrowleyml@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/4a6268ff-3340-453a-9bf5-c98d51a6f729@app.fastmail.com
Backpatch-through: 13

1 files changed, 15 insertions, 4 deletions

diff --git a/src/backend/executor/nodeTidscan.c b/src/backend/executor/nodeTidscan.c
index 5e56e29a15f..d50c6600358 100644
--- a/src/backend/executor/nodeTidscan.c
+++ b/src/backend/executor/nodeTidscan.c
@@ -402,12 +402,23 @@ TidNext(TidScanState *node)
 static bool
 TidRecheck(TidScanState *node, TupleTableSlot *slot)
 {
+	ItemPointer match;
+
+	/* WHERE CURRENT OF always intends to resolve to the latest tuple */
+	if (node->tss_isCurrentOf)
+		return true;
+
+	if (node->tss_TidList == NULL)
+		TidListEval(node);
+
 	/*
-	 * XXX shouldn't we check here to make sure tuple matches TID list? In
-	 * runtime-key case this is not certain, is it?  However, in the WHERE
-	 * CURRENT OF case it might not match anyway ...
+	 * Binary search the TidList to see if this ctid is mentioned and return
+	 * true if it is.
 	 */
-	return true;
+	match = (ItemPointer) bsearch(&slot->tts_tid, node->tss_TidList,
+								  node->tss_NumTids, sizeof(ItemPointerData),
+								  itemptr_comparator);
+	return match != NULL;
 }