Re: BUG #17949: Adding an index introduces serialisation anomalies. - Mailing list pgsql-bugs

On Mon, Jun 19, 2023 at 6:50 PM Thomas Munro <thomas.munro@gmail.com> wrote:
> ... or bitmap heapscan not checking for
> conflicts out comprehensively (xids on invisible tuples we scan), eg
> not fetching heap tuples for some short cut reason somewhere. ...

Ahh, here's such a place.  I can't reproduce it with the patch already
posted + this check commented out.

--- a/src/backend/access/heap/heapam_handler.c
+++ b/src/backend/access/heap/heapam_handler.c
@@ -2127,16 +2127,18 @@ heapam_scan_bitmap_next_block(TableScanDesc scan,

        hscan->rs_cindex = 0;
        hscan->rs_ntuples = 0;

+#if 0
        /*
         * Ignore any claimed entries past what we think is the end of the
         * relation. It may have been extended after the start of our scan (we
         * only hold an AccessShareLock, and it could be inserts from this
         * backend).
         */
        if (block >= hscan->rs_nblocks)
                return false;
+#endif