diff options
Diffstat (limited to 'src/include/utils/hsearch.h')
| -rw-r--r-- | src/include/utils/hsearch.h | 33 |
1 files changed, 18 insertions, 15 deletions
diff --git a/src/include/utils/hsearch.h b/src/include/utils/hsearch.h index f0a8009776..96efd88748 100644 --- a/src/include/utils/hsearch.h +++ b/src/include/utils/hsearch.h @@ -6,7 +6,7 @@ * * Copyright (c) 1994, Regents of the University of California * - * $Id: hsearch.h,v 1.9 1998/09/01 04:39:12 momjian Exp $ + * $Id: hsearch.h,v 1.9.2.1 1999/03/07 02:01:09 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -16,16 +16,23 @@ /* * Constants + * + * A hash table has a top-level "directory", each of whose entries points + * to a "segment" of ssize bucket headers. The maximum number of hash + * buckets is thus dsize * ssize (but dsize may be expansible). Of course, + * the number of records in the table can be larger, but we don't want a + * 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. */ -#define DEF_BUCKET_SIZE 256 -#define DEF_BUCKET_SHIFT 8/* log2(BUCKET) */ #define DEF_SEGSIZE 256 -#define DEF_SEGSIZE_SHIFT 8 /* log2(SEGSIZE) */ +#define DEF_SEGSIZE_SHIFT 8 /* log2(SEGSIZE) */ #define DEF_DIRSIZE 256 -#define PRIME1 37 +#define DEF_FFACTOR 1 /* default fill factor */ + +#define PRIME1 37 /* for the hash function */ #define PRIME2 1048583 -#define DEF_FFACTOR 1 -#define SPLTMAX 8 /* @@ -46,10 +53,8 @@ typedef unsigned long SEG_OFFSET; typedef struct hashhdr { - long bsize; /* Bucket/Page Size */ - long bshift; /* Bucket shift */ long dsize; /* Directory Size */ - long ssize; /* Segment Size */ + long ssize; /* Segment Size --- must be power of 2 */ long sshift; /* Segment shift */ long max_bucket; /* ID of Maximum bucket in use */ long high_mask; /* Mask to modulo into entire table */ @@ -59,8 +64,7 @@ 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 */ + long max_dsize; /* 'dsize' limit if directory is fixed size */ BUCKET_INDEX freeBucketIndex; /* index of first free bucket */ #ifdef HASH_STATISTICS @@ -83,14 +87,13 @@ typedef struct htab typedef struct hashctl { - long bsize; /* Bucket Size */ long ssize; /* Segment Size */ long dsize; /* Dirsize Size */ long ffactor; /* Fill factor */ long (*hash) (); /* Hash Function */ long keysize; /* hash key length in bytes */ long datasize; /* elem data length in bytes */ - long max_size; /* limit to dsize if directory size is + long max_dsize; /* limit to dsize if directory size is * limited */ long *segbase; /* base for calculating bucket + seg ptrs */ long *(*alloc) (); /* memory allocation function */ @@ -100,7 +103,6 @@ typedef struct hashctl } HASHCTL; /* Flags to indicate action for hctl */ -#define HASH_BUCKET 0x001 /* Setting bucket size */ #define HASH_SEGMENT 0x002 /* Setting segment size */ #define HASH_DIRSIZE 0x004 /* Setting directory size */ #define HASH_FFACTOR 0x008 /* Setting fill factor */ @@ -136,6 +138,7 @@ extern void hash_stats(char *where, HTAB *hashp); 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); /* * prototypes from functions in hashfn.c |