diff options
Diffstat (limited to 'src/backend/storage/buffer/buf_table.c')
| -rw-r--r-- | src/backend/storage/buffer/buf_table.c | 41 |
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) |