From d54a94b806825a119be86d5f73232b06dd9e9a16 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Fri, 30 Nov 2012 17:02:29 -0500
Subject: [PATCH] Take buffer lock while inspecting btree index pages in
contrib/pageinspect.
It's not safe to examine a shared buffer without any lock.
---
contrib/pageinspect/btreefuncs.c | 20 +++++++++++---------
1 file changed, 11 insertions(+), 9 deletions(-)
diff --git a/contrib/pageinspect/btreefuncs.c b/contrib/pageinspect/btreefuncs.c
index dbb2158ba8d..bc34af9b3c7 100644
--- a/contrib/pageinspect/btreefuncs.c
+++ b/contrib/pageinspect/btreefuncs.c
@@ -156,9 +156,9 @@ GetBTPageStatistics(BlockNumber blkno, Buffer buffer, BTPageStat *stat)
}
/* -----------------------------------------------
- * bt_page()
+ * bt_page_stats()
*
- * Usage: SELECT * FROM bt_page('t1_pkey', 1);
+ * Usage: SELECT * FROM bt_page_stats('t1_pkey', 1);
* -----------------------------------------------
*/
Datum
@@ -204,6 +204,7 @@ bt_page_stats(PG_FUNCTION_ARGS)
CHECK_RELATION_BLOCK_RANGE(rel, blkno);
buffer = ReadBuffer(rel, blkno);
+ LockBuffer(buffer, BUFFER_LOCK_SHARE);
/* keep compiler quiet */
stat.btpo_prev = stat.btpo_next = InvalidBlockNumber;
@@ -211,6 +212,9 @@ bt_page_stats(PG_FUNCTION_ARGS)
GetBTPageStatistics(blkno, buffer, &stat);
+ UnlockReleaseBuffer(buffer);
+ relation_close(rel, AccessShareLock);
+
/* Build a tuple descriptor for our result type */
if (get_call_result_type(fcinfo, NULL, &tupleDesc) != TYPEFUNC_COMPOSITE)
elog(ERROR, "return type must be a row type");
@@ -247,10 +251,6 @@ bt_page_stats(PG_FUNCTION_ARGS)
result = HeapTupleGetDatum(tuple);
- ReleaseBuffer(buffer);
-
- relation_close(rel, AccessShareLock);
-
PG_RETURN_DATUM(result);
}
@@ -322,6 +322,7 @@ bt_page_items(PG_FUNCTION_ARGS)
CHECK_RELATION_BLOCK_RANGE(rel, blkno);
buffer = ReadBuffer(rel, blkno);
+ LockBuffer(buffer, BUFFER_LOCK_SHARE);
/*
* We copy the page into local storage to avoid holding pin on the
@@ -335,7 +336,7 @@ bt_page_items(PG_FUNCTION_ARGS)
uargs->page = palloc(BLCKSZ);
memcpy(uargs->page, BufferGetPage(buffer), BLCKSZ);
- ReleaseBuffer(buffer);
+ UnlockReleaseBuffer(buffer);
relation_close(rel, AccessShareLock);
uargs->offset = FirstOffsetNumber;
@@ -466,6 +467,8 @@ bt_metap(PG_FUNCTION_ARGS)
errmsg("cannot access temporary tables of other sessions")));
buffer = ReadBuffer(rel, 0);
+ LockBuffer(buffer, BUFFER_LOCK_SHARE);
+
page = BufferGetPage(buffer);
metad = BTPageGetMeta(page);
@@ -492,8 +495,7 @@ bt_metap(PG_FUNCTION_ARGS)
result = HeapTupleGetDatum(tuple);
- ReleaseBuffer(buffer);
-
+ UnlockReleaseBuffer(buffer);
relation_close(rel, AccessShareLock);
PG_RETURN_DATUM(result);
--
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