@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $ PostgreSQL : pgsql / src / backend / utils / hash / dynahash . c , v 1.60 2005 / 05 / 16 00 : 19 : 04 tgl Exp $
* $ PostgreSQL : pgsql / src / backend / utils / hash / dynahash . c , v 1.61 2005 / 05 / 29 04 : 23 : 06 tgl Exp $
*
* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
*/
@ -498,22 +498,22 @@ calc_bucket(HASHHDR *hctl, uint32 hash_val)
* action is one of :
* HASH_FIND : look up key in table
* HASH_ENTER : look up key in table , creating entry if not present
* HASH_ENTER_NULL : same , but return NULL if out of memory
* HASH_REMOVE : look up key in table , remove entry if present
* HASH_FIND_SAVE : look up key in table , also save in static var
* HASH_REMOVE_SAVED : remove entry saved by HASH_FIND_SAVE
*
* Return value is a pointer to the element found / entered / removed if any ,
* or NULL if no match was found . ( NB : in the case of the REMOVE actions ,
* or NULL if no match was found . ( NB : in the case of the REMOVE action ,
* the result is a dangling pointer that shouldn ' t be dereferenced ! )
* A NULL result for HASH_ENTER implies we ran out of memory .
*
* HASH_ENTER will normally ereport a generic " out of memory " error if
* it is unable to create a new entry . The HASH_ENTER_NULL operation is
* the same except it will return NULL if out of memory . Note that
* HASH_ENTER_NULL cannot be used with the default palloc - based allocator ,
* since palloc internally ereports on out - of - memory .
*
* If foundPtr isn ' t NULL , then * foundPtr is set TRUE if we found an
* existing entry in the table , FALSE otherwise . This is needed in the
* HASH_ENTER case , but is redundant with the return value otherwise .
*
* The HASH_FIND_SAVE / HASH_REMOVE_SAVED interface is a hack to save one
* table lookup in a find / process / remove scenario . Note that no other
* addition or removal in the table can safely happen in between .
* - - - - - - - - - -
*/
void *
@ -523,19 +523,15 @@ hash_search(HTAB *hashp,
bool * foundPtr )
{
HASHHDR * hctl = hashp - > hctl ;
uint32 hashvalue = 0 ;
Size keysize = hctl - > keysize ;
uint32 hashvalue ;
uint32 bucket ;
long segment_num ;
long segment_ndx ;
HASHSEGMENT segp ;
HASHBUCKET currBucket ;
HASHBUCKET * prevBucketPtr ;
static struct State
{
HASHBUCKET currBucket ;
HASHBUCKET * prevBucketPtr ;
} saveState ;
HashCompareFunc match ;
# if HASH_STATISTICS
hash_accesses + + ;
@ -543,54 +539,38 @@ hash_search(HTAB *hashp,
# endif
/*
* Do the initial lookup ( or recall result of prior lookup )
* Do the initial lookup
*/
if ( action = = HASH_REMOVE_SAVED )
{
currBucket = saveState . currBucket ;
prevBucketPtr = saveState . prevBucketPtr ;
hashvalue = hashp - > hash ( keyPtr , keysize ) ;
bucket = calc_bucket ( hctl , hashvalue ) ;
/*
* Try to catch subsequent errors
*/
Assert ( currBucket ) ;
saveState . currBucket = NULL ;
}
else
{
HashCompareFunc match ;
Size keysize = hctl - > keysize ;
segment_num = bucket > > hctl - > sshift ;
segment_ndx = MOD ( bucket , hctl - > ssize ) ;
hashvalue = hashp - > hash ( keyPtr , keysize ) ;
bucket = calc_bucket ( hctl , hashvalue ) ;
segp = hashp - > dir [ segment_num ] ;
segment_num = bucket > > hctl - > sshift ;
segment_ndx = MOD ( bucket , hctl - > ssize ) ;
if ( segp = = NULL )
hash_corrupted ( hashp ) ;
segp = hashp - > dir [ segment_num ] ;
prevBucketPtr = & segp [ segment_ndx ] ;
currBucket = * prevBucketPtr ;
if ( segp = = NULL )
hash_corrupted ( hashp ) ;
/*
* Follow collision chain looking for matching key
*/
match = hashp - > match ; /* save one fetch in inner loop */
prevBucketPtr = & segp [ segment_ndx ] ;
while ( currBucket ! = NULL )
{
if ( currBucket - > hashvalue = = hashvalue & &
match ( ELEMENTKEY ( currBucket ) , keyPtr , keysize ) = = 0 )
break ;
prevBucketPtr = & ( currBucket - > link ) ;
currBucket = * prevBucketPtr ;
/*
* Follow collision chain looking for matching key
*/
match = hashp - > match ; /* save one fetch in inner loop */
while ( currBucket ! = NULL )
{
if ( currBucket - > hashvalue = = hashvalue & &
match ( ELEMENTKEY ( currBucket ) , keyPtr , keysize ) = = 0 )
break ;
prevBucketPtr = & ( currBucket - > link ) ;
currBucket = * prevBucketPtr ;
# if HASH_STATISTICS
hash_collisions + + ;
hctl - > collisions + + ;
hash_collisions + + ;
hctl - > collisions + + ;
# endif
}
}
if ( foundPtr )
@ -606,17 +586,7 @@ hash_search(HTAB *hashp,
return ( void * ) ELEMENTKEY ( currBucket ) ;
return NULL ;
case HASH_FIND_SAVE :
if ( currBucket ! = NULL )
{
saveState . currBucket = currBucket ;
saveState . prevBucketPtr = prevBucketPtr ;
return ( void * ) ELEMENTKEY ( currBucket ) ;
}
return NULL ;
case HASH_REMOVE :
case HASH_REMOVE_SAVED :
if ( currBucket ! = NULL )
{
Assert ( hctl - > nentries > 0 ) ;
@ -638,6 +608,11 @@ hash_search(HTAB *hashp,
}
return NULL ;
case HASH_ENTER_NULL :
/* ENTER_NULL does not work with palloc-based allocator */
Assert ( hashp - > alloc ! = DynaHashAlloc ) ;
/* FALL THRU */
case HASH_ENTER :
/* Return existing element if found, else create one */
if ( currBucket ! = NULL )
@ -649,7 +624,20 @@ hash_search(HTAB *hashp,
{
/* no free elements. allocate another chunk of buckets */
if ( ! element_alloc ( hashp , HASHELEMENT_ALLOC_INCR ) )
return NULL ; /* out of memory */
{
/* out of memory */
if ( action = = HASH_ENTER_NULL )
return NULL ;
/* report a generic message */
if ( hashp - > isshared )
ereport ( ERROR ,
( errcode ( ERRCODE_OUT_OF_MEMORY ) ,
errmsg ( " out of shared memory " ) ) ) ;
else
ereport ( ERROR ,
( errcode ( ERRCODE_OUT_OF_MEMORY ) ,
errmsg ( " out of memory " ) ) ) ;
}
currBucket = hctl - > freeList ;
Assert ( currBucket ! = NULL ) ;
}
Tom Lane
20 years ago