From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Thu, 17 Nov 2005 17:42:24 +0000 (+0000)
Subject: DropRelFileNodeBuffers failed to fix the state of the lookup hash table
X-Git-Url: http://waps.l3s.uni-hannover.de/gitweb/?a=commitdiff_plain;h=b0d6ee4d91b6b0646462eb2fc69320919d144fcb;p=users%2Fbernd%2Fpostgres.git

DropRelFileNodeBuffers failed to fix the state of the lookup hash table
that was added to localbuf.c in 8.1; therefore, applying it to a temp table
left corrupt lookup state in memory.  The only case where this had a
significant chance of causing problems was an ON COMMIT DELETE ROWS temp
table; the other possible paths left bogus state that was unlikely to
be used again.  Per report from Csaba Nagy.
---

diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index bbcc429a89..730cc84c18 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -1384,34 +1384,17 @@ DropRelFileNodeBuffers(RelFileNode rnode, bool istemp,
 					   BlockNumber firstDelBlock)
 {
 	int			i;
-	volatile BufferDesc *bufHdr;
 
 	if (istemp)
 	{
-		for (i = 0; i < NLocBuffer; i++)
-		{
-			bufHdr = &LocalBufferDescriptors[i];
-			if (RelFileNodeEquals(bufHdr->tag.rnode, rnode) &&
-				bufHdr->tag.blockNum >= firstDelBlock)
-			{
-				if (LocalRefCount[i] != 0)
-					elog(ERROR, "block %u of %u/%u/%u is still referenced (local %u)",
-						 bufHdr->tag.blockNum,
-						 bufHdr->tag.rnode.spcNode,
-						 bufHdr->tag.rnode.dbNode,
-						 bufHdr->tag.rnode.relNode,
-						 LocalRefCount[i]);
-				CLEAR_BUFFERTAG(bufHdr->tag);
-				bufHdr->flags = 0;
-				bufHdr->usage_count = 0;
-			}
-		}
+		DropRelFileNodeLocalBuffers(rnode, firstDelBlock);
 		return;
 	}
 
 	for (i = 0; i < NBuffers; i++)
 	{
-		bufHdr = &BufferDescriptors[i];
+		volatile BufferDesc *bufHdr = &BufferDescriptors[i];
+
 		LockBufHdr(bufHdr);
 		if (RelFileNodeEquals(bufHdr->tag.rnode, rnode) &&
 			bufHdr->tag.blockNum >= firstDelBlock)
diff --git a/src/backend/storage/buffer/localbuf.c b/src/backend/storage/buffer/localbuf.c
index 463b126051..95eb359c8d 100644
--- a/src/backend/storage/buffer/localbuf.c
+++ b/src/backend/storage/buffer/localbuf.c
@@ -241,6 +241,52 @@ WriteLocalBuffer(Buffer buffer, bool release)
 	}
 }
 
+/*
+ * DropRelFileNodeLocalBuffers
+ *		This function removes from the buffer pool all the pages of the
+ *		specified relation that have block numbers >= firstDelBlock.
+ *		(In particular, with firstDelBlock = 0, all pages are removed.)
+ *		Dirty pages are simply dropped, without bothering to write them
+ *		out first.	Therefore, this is NOT rollback-able, and so should be
+ *		used only with extreme caution!
+ *
+ *		See DropRelFileNodeBuffers in bufmgr.c for more notes.
+ */
+void
+DropRelFileNodeLocalBuffers(RelFileNode rnode, BlockNumber firstDelBlock)
+{
+	int			i;
+
+	for (i = 0; i < NLocBuffer; i++)
+	{
+		BufferDesc *bufHdr = &LocalBufferDescriptors[i];
+		LocalBufferLookupEnt *hresult;
+
+		if ((bufHdr->flags & BM_TAG_VALID) &&
+			RelFileNodeEquals(bufHdr->tag.rnode, rnode) &&
+			bufHdr->tag.blockNum >= firstDelBlock)
+		{
+			if (LocalRefCount[i] != 0)
+				elog(ERROR, "block %u of %u/%u/%u is still referenced (local %u)",
+					 bufHdr->tag.blockNum,
+					 bufHdr->tag.rnode.spcNode,
+					 bufHdr->tag.rnode.dbNode,
+					 bufHdr->tag.rnode.relNode,
+					 LocalRefCount[i]);
+			/* Remove entry from hashtable */
+			hresult = (LocalBufferLookupEnt *)
+				hash_search(LocalBufHash, (void *) &bufHdr->tag,
+							HASH_REMOVE, NULL);
+			if (!hresult)			/* shouldn't happen */
+				elog(ERROR, "local buffer hash table corrupted");
+			/* Mark buffer invalid */
+			CLEAR_BUFFERTAG(bufHdr->tag);
+			bufHdr->flags = 0;
+			bufHdr->usage_count = 0;
+		}
+	}
+}
+
 /*
  * InitLocalBuffers -
  *	  init the local buffer cache. Since most queries (esp. multi-user ones)
diff --git a/src/include/storage/buf_internals.h b/src/include/storage/buf_internals.h
index 47b0cfe6c2..8618a9c7e3 100644
--- a/src/include/storage/buf_internals.h
+++ b/src/include/storage/buf_internals.h
@@ -198,6 +198,8 @@ extern void BufTableDelete(BufferTag *tagPtr);
 extern BufferDesc *LocalBufferAlloc(Relation reln, BlockNumber blockNum,
 				 bool *foundPtr);
 extern void WriteLocalBuffer(Buffer buffer, bool release);
+extern void DropRelFileNodeLocalBuffers(RelFileNode rnode,
+										BlockNumber firstDelBlock);
 extern void AtEOXact_LocalBuffers(bool isCommit);
 
 #endif   /* BUFMGR_INTERNALS_H */