diff options
Diffstat (limited to 'src/include/utils/hsearch.h')
| -rw-r--r-- | src/include/utils/hsearch.h | 27 |
1 files changed, 14 insertions, 13 deletions
diff --git a/src/include/utils/hsearch.h b/src/include/utils/hsearch.h index 25e9bedb5cf..aa5f4603012 100644 --- a/src/include/utils/hsearch.h +++ b/src/include/utils/hsearch.h @@ -1,13 +1,13 @@ /*------------------------------------------------------------------------- * * hsearch.h - * for hashing in the new buffer manager + * for hash tables, particularly hash tables in shared memory * * * Portions Copyright (c) 1996-2000, PostgreSQL, Inc * Portions Copyright (c) 1994, Regents of the University of California * - * $Id: hsearch.h,v 1.13 2000/01/26 05:58:38 momjian Exp $ + * $Id: hsearch.h,v 1.14 2000/02/26 05:25:53 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -25,12 +25,15 @@ * whole lot of records per bucket or performance goes down. * * In a hash table allocated in shared memory, the directory cannot be - * expanded because it must stay at a fixed address. + * expanded because it must stay at a fixed address. The directory size + * should be selected using hash_select_dirsize (and you'd better have + * a good idea of the maximum number of entries!). For non-shared hash + * tables, the initial directory size can be left at the default. */ #define DEF_SEGSIZE 256 -#define DEF_SEGSIZE_SHIFT 8/* log2(SEGSIZE) */ +#define DEF_SEGSIZE_SHIFT 8 /* must be log2(DEF_SEGSIZE) */ #define DEF_DIRSIZE 256 -#define DEF_FFACTOR 1/* default fill factor */ +#define DEF_FFACTOR 1 /* default fill factor */ #define PRIME1 37 /* for the hash function */ #define PRIME2 1048583 @@ -42,13 +45,13 @@ */ typedef struct element { - unsigned long next; /* secret from user */ + unsigned long next; /* secret from user */ long key; } ELEMENT; typedef unsigned long BUCKET_INDEX; -/* segment is an array of bucket pointers */ +/* segment is an array of bucket pointers */ typedef BUCKET_INDEX *SEGMENT; typedef unsigned long SEG_OFFSET; @@ -65,10 +68,8 @@ typedef struct hashhdr long nsegs; /* Number of allocated segments */ long keysize; /* hash key length in bytes */ long datasize; /* elem data length in bytes */ - long max_dsize; /* 'dsize' limit if directory is fixed - * size */ - BUCKET_INDEX freeBucketIndex; - /* index of first free bucket */ + long max_dsize; /* 'dsize' limit if directory is fixed size */ + BUCKET_INDEX freeBucketIndex; /* index of first free bucket */ #ifdef HASH_STATISTICS long accesses; long collisions; @@ -84,7 +85,6 @@ typedef struct htab SEG_OFFSET *dir; /* 'directory' of segm starts */ long *(*alloc) (); /* memory allocator (long * for alignment * reasons) */ - } HTAB; typedef struct hashctl @@ -115,7 +115,7 @@ typedef struct hashctl #define HASH_ALLOC 0x100 /* Setting memory allocator */ -/* seg_alloc assumes that INVALID_INDEX is 0*/ +/* seg_alloc assumes that INVALID_INDEX is 0 */ #define INVALID_INDEX (0) #define NO_MAX_DSIZE (-1) /* number of hash buckets allocated at once */ @@ -141,6 +141,7 @@ extern long *hash_search(HTAB *hashp, char *keyPtr, HASHACTION action, bool *foundPtr); extern long *hash_seq(HTAB *hashp); extern long hash_estimate_size(long num_entries, long keysize, long datasize); +extern long hash_select_dirsize(long num_entries); /* * prototypes from functions in hashfn.c |