Ensure that XLOG_HEAP2_VISIBLE always targets an initialized page.

Andres Freund

diff --git a/src/backend/commands/vacuumlazy.c b/src/backend/commands/vacuumlazy.c
index 9254bcd68688ecd0a8ca5a6f164734ea340188e2..ff8764b4a145788a26c393bdaf7576bfab53eeac 100644 (file)
--- a/src/backend/commands/vacuumlazy.c
+++ b/src/backend/commands/vacuumlazy.c
@@ -650,6 +650,24 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
            /* empty pages are always all-visible */
            if (!PageIsAllVisible(page))
            {
+               /*
+                * It's possible that another backend has extended the heap,
+                * initialized the page, and then failed to WAL-log the page
+                * due to an ERROR.  Since heap extension is not WAL-logged,
+                * recovery might try to replay our record setting the
+                * page all-visible and find that the page isn't initialized,
+                * which will cause a PANIC.  To prevent that, check whether
+                * the page has been previously WAL-logged, and if not, do that
+                * now.
+                *
+                * XXX: It would be nice to use a logging method supporting
+                * standard buffers here since log_newpage_buffer() will write
+                * the full block instead of omitting the hole.
+                */
+               if (RelationNeedsWAL(onerel) &&
+                   XLByteEQ(PageGetLSN(page), InvalidXLogRecPtr))
+                   log_newpage_buffer(buf);
+
                PageSetAllVisible(page);
                MarkBufferDirty(buf);
                visibilitymap_set(onerel, blkno, InvalidXLogRecPtr, vmbuffer,