From 17fa4c321ccf9693de406faffe6b235e949aa25f Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Thu, 6 Jun 2013 10:15:45 -0400
Subject: [PATCH] Ensure that XLOG_HEAP2_VISIBLE always targets an initialized
page.
Andres Freund
---
src/backend/commands/vacuumlazy.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/src/backend/commands/vacuumlazy.c b/src/backend/commands/vacuumlazy.c
index 9254bcd6868..ff8764b4a14 100644
--- 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,
--
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