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Take buffer lock while inspecting btree index pages in contrib/pageinspect. 

It's not safe to examine a shared buffer without any lock.
This commit is contained in:
Tom Lane 2012-11-30 17:02:29 -05:00
parent b86327c1c5
commit d54a94b806
1 changed files with 11 additions and 9 deletions
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20
contrib/pageinspect/btreefuncs.c
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@ -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);