Code review for ARC patch. Eliminate static variables, improve handling

of VACUUM cases so that VACUUM requests don't affect the ARC state at all,
avoid corner case where BufferSync would uselessly rewrite a buffer that
no longer contains the page that was to be flushed.  Make some minor
other cleanups in and around the bufmgr as well, such as moving PinBuffer
and UnpinBuffer into bufmgr.c where they really belong.

1 files changed, 20 insertions, 24 deletions

diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c
index 33590b65fdb..3829444195b 100644
--- a/src/backend/storage/buffer/buf_table.c
+++ b/src/backend/storage/buffer/buf_table.c
@@ -3,46 +3,42 @@
  * buf_table.c
  *	  routines for finding buffers in the buffer pool.
  *
+ * NOTE: these days, what this table actually provides is a mapping from
+ * BufferTags to CDB indexes, not directly to buffers.  The function names
+ * are thus slight misnomers.
+ *
+ * Note: all routines in this file assume that the BufMgrLock is held
+ * by the caller, so no synchronization is needed.
+ *
+ *
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/buffer/buf_table.c,v 1.34 2003/12/14 00:34:47 neilc Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/buffer/buf_table.c,v 1.35 2004/04/19 23:27:17 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
-/*
- * OLD COMMENTS
- *
- * Data Structures:
- *
- *		Buffers are identified by their BufferTag (buf.h).	This
- * file contains routines for allocating a shmem hash table to
- * map buffer tags to buffer descriptors.
- *
- * Synchronization:
- *
- *	All routines in this file assume BufMgrLock is held by their caller.
- */
-
 #include "postgres.h"
 
 #include "storage/buf_internals.h"
 #include "storage/bufmgr.h"
 
+
 static HTAB *SharedBufHash;
 
 
 /*
  * Initialize shmem hash table for mapping buffers
+ *		size is the desired hash table size (2*NBuffers for ARC algorithm)
  */
 void
 InitBufTable(int size)
 {
 	HASHCTL		info;
 
-	/* assume lock is held */
+	/* assume no locking is needed yet */
 
 	/* BufferTag maps to Buffer */
 	info.keysize = sizeof(BufferTag);
@@ -60,6 +56,7 @@ InitBufTable(int size)
 
 /*
  * BufTableLookup
+ *		Lookup the given BufferTag; return CDB index, or -1 if not found
  */
 int
 BufTableLookup(BufferTag *tagPtr)
@@ -78,10 +75,11 @@ BufTableLookup(BufferTag *tagPtr)
 }
 
 /*
- * BufTableDelete
+ * BufTableInsert
+ *		Insert a hashtable entry for given tag and CDB index
  */
-bool
-BufTableInsert(BufferTag *tagPtr, Buffer buf_id)
+void
+BufTableInsert(BufferTag *tagPtr, int cdb_id)
 {
 	BufferLookupEnt *result;
 	bool		found;
@@ -97,14 +95,14 @@ BufTableInsert(BufferTag *tagPtr, Buffer buf_id)
 	if (found)					/* found something else in the table? */
 		elog(ERROR, "shared buffer hash table corrupted");
 
-	result->id = buf_id;
-	return TRUE;
+	result->id = cdb_id;
 }
 
 /*
  * BufTableDelete
+ *		Delete the hashtable entry for given tag
  */
-bool
+void
 BufTableDelete(BufferTag *tagPtr)
 {
 	BufferLookupEnt *result;
@@ -114,6 +112,4 @@ BufTableDelete(BufferTag *tagPtr)
 
 	if (!result)				/* shouldn't happen */
 		elog(ERROR, "shared buffer hash table corrupted");
-
-	return TRUE;
 }