Ensure that all details of the ARC algorithm are hidden within freelist.c.

This refactoring does not change any algorithms or data structures, just
remove visibility of the ARC datastructures from other source files.

1 files changed, 29 insertions, 12 deletions

diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c
index 12ac6aba886..ef79ae9c393 100644
--- a/src/backend/storage/buffer/buf_table.c
+++ b/src/backend/storage/buffer/buf_table.c
@@ -1,11 +1,11 @@
 /*-------------------------------------------------------------------------
  *
  * buf_table.c
- *	  routines for finding buffers in the buffer pool.
+ *	  routines for mapping BufferTags to buffer indexes.
  *
- * 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: this module is called only by freelist.c, and the "buffer IDs"
+ * it deals with are whatever freelist.c needs them to be; they may not be
+ * directly equivalent to Buffer numbers.
  *
  * Note: all routines in this file assume that the BufMgrLock is held
  * by the caller, so no synchronization is needed.
@@ -16,7 +16,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/buffer/buf_table.c,v 1.38 2004/12/31 22:00:49 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/buffer/buf_table.c,v 1.39 2005/02/03 23:29:11 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -26,12 +26,29 @@
 #include "storage/bufmgr.h"
 
 
+/* entry for buffer lookup hashtable */
+typedef struct
+{
+	BufferTag	key;			/* Tag of a disk page */
+	int			id;				/* Associated buffer ID */
+} BufferLookupEnt;
+
 static HTAB *SharedBufHash;
 
 
 /*
+ * Estimate space needed for mapping hashtable
+ *		size is the desired hash table size (possibly more than NBuffers)
+ */
+int
+BufTableShmemSize(int size)
+{
+	return hash_estimate_size(size, sizeof(BufferLookupEnt));
+}
+
+/*
  * Initialize shmem hash table for mapping buffers
- *		size is the desired hash table size (2*NBuffers for ARC algorithm)
+ *		size is the desired hash table size (possibly more than NBuffers)
  */
 void
 InitBufTable(int size)
@@ -56,7 +73,7 @@ InitBufTable(int size)
 
 /*
  * BufTableLookup
- *		Lookup the given BufferTag; return CDB index, or -1 if not found
+ *		Lookup the given BufferTag; return buffer ID, or -1 if not found
  */
 int
 BufTableLookup(BufferTag *tagPtr)
@@ -76,10 +93,10 @@ BufTableLookup(BufferTag *tagPtr)
 
 /*
  * BufTableInsert
- *		Insert a hashtable entry for given tag and CDB index
+ *		Insert a hashtable entry for given tag and buffer ID
  */
 void
-BufTableInsert(BufferTag *tagPtr, int cdb_id)
+BufTableInsert(BufferTag *tagPtr, int buf_id)
 {
 	BufferLookupEnt *result;
 	bool		found;
@@ -92,15 +109,15 @@ BufTableInsert(BufferTag *tagPtr, int cdb_id)
 				(errcode(ERRCODE_OUT_OF_MEMORY),
 				 errmsg("out of shared memory")));
 
-	if (found)					/* found something else in the table? */
+	if (found)					/* found something already in the table? */
 		elog(ERROR, "shared buffer hash table corrupted");
 
-	result->id = cdb_id;
+	result->id = buf_id;
 }
 
 /*
  * BufTableDelete
- *		Delete the hashtable entry for given tag
+ *		Delete the hashtable entry for given tag (which must exist)
  */
 void
 BufTableDelete(BufferTag *tagPtr)