Fix determination of broken LSN in OVERWRITTEN_CONTRECORD

In commit ff9f111bce24 I mixed up inconsistent definitions of the LSN of
the first record in a page, when the previous record ends exactly at the
page boundary.  The correct LSN is adjusted to skip the WAL page header;
I failed to use that when setting XLogReaderState->overwrittenRecPtr,
so at WAL replay time VerifyOverwriteContrecord would refuse to let
replay continue past that record.

Backpatch to 10.  9.6 also contains this bug, but it's no longer being
maintained.

Discussion: https://postgr.es/m/45597.1637694259@sss.pgh.pa.us

diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index f39f8044a96256ebe7ac95354329c933f399dba8..3a7de025657ebed9b51953b825915825054aae9c 100644 (file)
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -467,7 +467,7 @@ restart:
             */
            if (pageHeader->xlp_info & XLP_FIRST_IS_OVERWRITE_CONTRECORD)
            {
-               state->overwrittenRecPtr = state->currRecPtr;
+               state->overwrittenRecPtr = RecPtr;
                ResetDecoder(state);
                RecPtr = targetPagePtr;
                goto restart;