Replacement of the buffer replacement strategy with an ARC

algorithm adopted for PostgreSQL.

Jan

1 files changed, 26 insertions, 42 deletions

diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c
index 072288e330e..a2318a29f36 100644
--- a/src/backend/storage/buffer/buf_table.c
+++ b/src/backend/storage/buffer/buf_table.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/buffer/buf_table.c,v 1.29 2003/08/04 02:40:03 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/buffer/buf_table.c,v 1.30 2003/11/13 00:40:01 wieck Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -38,7 +38,7 @@ static HTAB *SharedBufHash;
  * Initialize shmem hash table for mapping buffers
  */
 void
-InitBufTable(void)
+InitBufTable(int size)
 {
 	HASHCTL		info;
 
@@ -50,7 +50,7 @@ InitBufTable(void)
 	info.hash = tag_hash;
 
 	SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table",
-								  NBuffers, NBuffers,
+								  size, size,
 								  &info,
 								  HASH_ELEM | HASH_FUNCTION);
 
@@ -58,79 +58,63 @@ InitBufTable(void)
 		elog(FATAL, "could not initialize shared buffer hash table");
 }
 
-BufferDesc *
+/*
+ * BufTableLookup
+ */
+int
 BufTableLookup(BufferTag *tagPtr)
 {
 	BufferLookupEnt *result;
 
 	if (tagPtr->blockNum == P_NEW)
-		return NULL;
+		return -1;
 
 	result = (BufferLookupEnt *)
 		hash_search(SharedBufHash, (void *) tagPtr, HASH_FIND, NULL);
 	if (!result)
-		return NULL;
+		return -1;
 
-	return &(BufferDescriptors[result->id]);
+	return result->id;
 }
 
 /*
  * BufTableDelete
  */
 bool
-BufTableDelete(BufferDesc *buf)
+BufTableInsert(BufferTag *tagPtr, Buffer buf_id)
 {
 	BufferLookupEnt *result;
-
-	/*
-	 * buffer not initialized or has been removed from table already.
-	 * BM_DELETED keeps us from removing buffer twice.
-	 */
-	if (buf->flags & BM_DELETED)
-		return TRUE;
-
-	buf->flags |= BM_DELETED;
+	bool		found;
 
 	result = (BufferLookupEnt *)
-		hash_search(SharedBufHash, (void *) &(buf->tag), HASH_REMOVE, NULL);
+		hash_search(SharedBufHash, (void *) tagPtr, HASH_ENTER, &found);
 
-	if (!result)				/* shouldn't happen */
-		elog(ERROR, "shared buffer hash table corrupted");
+	if (!result)
+		ereport(ERROR,
+				(errcode(ERRCODE_OUT_OF_MEMORY),
+				 errmsg("out of shared memory")));
 
-	/*
-	 * Clear the buffer's tag.  This doesn't matter for the hash table,
-	 * since the buffer is already removed from it, but it ensures that
-	 * sequential searches through the buffer table won't think the buffer
-	 * is still valid for its old page.
-	 */
-	buf->tag.rnode.relNode = InvalidOid;
-	buf->tag.rnode.tblNode = InvalidOid;
+	if (found)					/* found something else in the table? */
+		elog(ERROR, "shared buffer hash table corrupted");
 
+	result->id = buf_id;
 	return TRUE;
 }
 
+/*
+ * BufTableDelete
+ */
 bool
-BufTableInsert(BufferDesc *buf)
+BufTableDelete(BufferTag *tagPtr)
 {
 	BufferLookupEnt *result;
-	bool		found;
-
-	/* cannot insert it twice */
-	Assert(buf->flags & BM_DELETED);
-	buf->flags &= ~(BM_DELETED);
 
 	result = (BufferLookupEnt *)
-		hash_search(SharedBufHash, (void *) &(buf->tag), HASH_ENTER, &found);
-
-	if (!result)
-		ereport(ERROR,
-				(errcode(ERRCODE_OUT_OF_MEMORY),
-				 errmsg("out of shared memory")));
+		hash_search(SharedBufHash, (void *) tagPtr, HASH_REMOVE, NULL);
 
-	if (found)					/* found something else in the table? */
+	if (!result)				/* shouldn't happen */
 		elog(ERROR, "shared buffer hash table corrupted");
 
-	result->id = buf->buf_id;
 	return TRUE;
 }