Correct serious bug in hashtable expansion routine: under the
right circumstances it would leave old and new bucket headers pointing to the same list of records.
This commit is contained in:
Tom Lane
parent
7f79496aa5
commit
86482e17bd
|
|
@ -7,7 +7,7 @@
|
|||
*
|
||||
*
|
||||
* IDENTIFICATION
|
||||
* $Header: /cvsroot/pgsql/src/backend/utils/hash/dynahash.c,v 1.22 1999/05/25 16:12:28 momjian Exp $
|
||||
* $Header: /cvsroot/pgsql/src/backend/utils/hash/dynahash.c,v 1.23 1999/05/31 17:01:52 tgl Exp $
|
||||
*
|
||||
*-------------------------------------------------------------------------
|
||||
*/
|
||||
|
|
@ -52,25 +52,23 @@
|
|||
#include "utils/memutils.h"
|
||||
|
||||
/*
|
||||
* Fast arithmetic, relying on powers of 2,
|
||||
* and on pre-processor concatenation property
|
||||
* Fast MOD arithmetic, assuming that y is a power of 2 !
|
||||
*/
|
||||
|
||||
#define MOD(x,y) ((x) & ((y)-1))
|
||||
|
||||
/*
|
||||
* external routines
|
||||
*/
|
||||
|
||||
/*
|
||||
* Private function prototypes
|
||||
*/
|
||||
static long *DynaHashAlloc(unsigned int size);
|
||||
static void DynaHashFree(Pointer ptr);
|
||||
static uint32 call_hash(HTAB *hashp, char *k, int len);
|
||||
static uint32 call_hash(HTAB *hashp, char *k);
|
||||
static SEG_OFFSET seg_alloc(HTAB *hashp);
|
||||
static int bucket_alloc(HTAB *hashp);
|
||||
static int dir_realloc(HTAB *hashp);
|
||||
static int expand_table(HTAB *hashp);
|
||||
static int hdefault(HTAB *hashp);
|
||||
static int init_htab(HTAB *hashp, int nelem);
|
||||
|
||||
typedef long *((*dhalloc_ptr) ());
|
||||
|
||||
|
|
@ -118,15 +116,6 @@ DynaHashFree(Pointer ptr)
|
|||
|
||||
#endif /* FRONTEND */
|
||||
|
||||
/* ----------------
|
||||
* Internal routines
|
||||
* ----------------
|
||||
*/
|
||||
|
||||
static int expand_table(HTAB *hashp);
|
||||
static int hdefault(HTAB *hashp);
|
||||
static int init_htab(HTAB *hashp, int nelem);
|
||||
|
||||
|
||||
/*
|
||||
* pointer access macros. Shared memory implementation cannot
|
||||
|
|
@ -220,6 +209,8 @@ hash_create(int nelem, HASHCTL *info, int flags)
|
|||
{
|
||||
hctl->ssize = info->ssize;
|
||||
hctl->sshift = my_log2(info->ssize);
|
||||
/* ssize had better be a power of 2 */
|
||||
Assert(hctl->ssize == (1L << hctl->sshift));
|
||||
}
|
||||
if (flags & HASH_FFACTOR)
|
||||
hctl->ffactor = info->ffactor;
|
||||
|
|
@ -412,6 +403,8 @@ hash_estimate_size(long num_entries, long keysize, long datasize)
|
|||
* XXX this sure looks thoroughly broken to me --- tgl 2/99.
|
||||
* It's freeing every entry individually --- but they weren't
|
||||
* allocated individually, see bucket_alloc!! Why doesn't it crash?
|
||||
* ANSWER: it probably does crash, but is never invoked in normal
|
||||
* operations...
|
||||
*/
|
||||
|
||||
void
|
||||
|
|
@ -479,14 +472,13 @@ hash_stats(char *where, HTAB *hashp)
|
|||
/*******************************SEARCH ROUTINES *****************************/
|
||||
|
||||
static uint32
|
||||
call_hash(HTAB *hashp, char *k, int len)
|
||||
call_hash(HTAB *hashp, char *k)
|
||||
{
|
||||
HHDR *hctl = hashp->hctl;
|
||||
long hash_val,
|
||||
bucket;
|
||||
HHDR *hctl;
|
||||
|
||||
hctl = hashp->hctl;
|
||||
hash_val = hashp->hash(k, len);
|
||||
hash_val = hashp->hash(k, (int) hctl->keysize);
|
||||
|
||||
bucket = hash_val & hctl->high_mask;
|
||||
if (bucket > hctl->max_bucket)
|
||||
|
|
@ -550,9 +542,9 @@ hash_search(HTAB *hashp,
|
|||
}
|
||||
else
|
||||
{
|
||||
bucket = call_hash(hashp, keyPtr, hctl->keysize);
|
||||
bucket = call_hash(hashp, keyPtr);
|
||||
segment_num = bucket >> hctl->sshift;
|
||||
segment_ndx = bucket & (hctl->ssize - 1);
|
||||
segment_ndx = MOD(bucket, hctl->ssize);
|
||||
|
||||
segp = GET_SEG(hashp, segment_num);
|
||||
|
||||
|
|
@ -598,8 +590,10 @@ hash_search(HTAB *hashp,
|
|||
Assert(hctl->nkeys > 0);
|
||||
hctl->nkeys--;
|
||||
|
||||
/* add the bucket to the freelist for this table. */
|
||||
/* remove record from hash bucket's chain. */
|
||||
*prevIndexPtr = curr->next;
|
||||
|
||||
/* add the record to the freelist for this table. */
|
||||
curr->next = hctl->freeBucketIndex;
|
||||
hctl->freeBucketIndex = currIndex;
|
||||
|
||||
|
|
@ -639,7 +633,6 @@ hash_search(HTAB *hashp,
|
|||
currIndex = hctl->freeBucketIndex;
|
||||
if (currIndex == INVALID_INDEX)
|
||||
{
|
||||
|
||||
/* no free elements. allocate another chunk of buckets */
|
||||
if (!bucket_alloc(hashp))
|
||||
return NULL;
|
||||
|
|
@ -722,7 +715,7 @@ hash_seq(HTAB *hashp)
|
|||
* initialize the search within this bucket.
|
||||
*/
|
||||
segment_num = curBucket >> hctl->sshift;
|
||||
segment_ndx = curBucket & (hctl->ssize - 1);
|
||||
segment_ndx = MOD(curBucket, hctl->ssize);
|
||||
|
||||
/*
|
||||
* first find the right segment in the table directory.
|
||||
|
|
@ -751,6 +744,10 @@ hash_seq(HTAB *hashp)
|
|||
|
||||
|
||||
/********************************* UTILITIES ************************/
|
||||
|
||||
/*
|
||||
* Expand the table by adding one more hash bucket.
|
||||
*/
|
||||
static int
|
||||
expand_table(HTAB *hashp)
|
||||
{
|
||||
|
|
@ -790,19 +787,31 @@ expand_table(HTAB *hashp)
|
|||
hctl->nsegs++;
|
||||
}
|
||||
|
||||
/* OK, we got a new bucket */
|
||||
/* OK, we created a new bucket */
|
||||
hctl->max_bucket++;
|
||||
old_bucket = (hctl->max_bucket & hctl->low_mask);
|
||||
|
||||
/*
|
||||
* *Before* changing masks, find old bucket corresponding to same hash
|
||||
* values; values in that bucket may need to be relocated to new bucket.
|
||||
* Note that new_bucket is certainly larger than low_mask at this point,
|
||||
* so we can skip the first step of the regular hash mask calc.
|
||||
*/
|
||||
old_bucket = (new_bucket & hctl->low_mask);
|
||||
|
||||
/*
|
||||
* If we crossed a power of 2, readjust masks.
|
||||
*/
|
||||
if (new_bucket > hctl->high_mask)
|
||||
{
|
||||
/* Starting a new doubling */
|
||||
hctl->low_mask = hctl->high_mask;
|
||||
hctl->high_mask = new_bucket | hctl->low_mask;
|
||||
}
|
||||
|
||||
/*
|
||||
* Relocate records to the new bucket
|
||||
* Relocate records to the new bucket. NOTE: because of the way the
|
||||
* hash masking is done in call_hash, only one old bucket can need to
|
||||
* be split at this point. With a different way of reducing the hash
|
||||
* value, that might not be true!
|
||||
*/
|
||||
old_segnum = old_bucket >> hctl->sshift;
|
||||
old_segndx = MOD(old_bucket, hctl->ssize);
|
||||
|
|
@ -816,12 +825,9 @@ expand_table(HTAB *hashp)
|
|||
chainIndex != INVALID_INDEX;
|
||||
chainIndex = nextIndex)
|
||||
{
|
||||
|
||||
chain = GET_BUCKET(hashp, chainIndex);
|
||||
nextIndex = chain->next;
|
||||
if (call_hash(hashp,
|
||||
(char *) &(chain->key),
|
||||
hctl->keysize) == old_bucket)
|
||||
if (call_hash(hashp, (char *) &(chain->key)) == old_bucket)
|
||||
{
|
||||
*old = chainIndex;
|
||||
old = &chain->next;
|
||||
|
|
@ -831,8 +837,10 @@ expand_table(HTAB *hashp)
|
|||
*newbi = chainIndex;
|
||||
newbi = &chain->next;
|
||||
}
|
||||
chain->next = INVALID_INDEX;
|
||||
}
|
||||
/* don't forget to terminate the rebuilt hash chains... */
|
||||
*old = INVALID_INDEX;
|
||||
*newbi = INVALID_INDEX;
|
||||
return 1;
|
||||
}
|
||||
|
||||
|
|
@ -907,15 +915,13 @@ bucket_alloc(HTAB *hashp)
|
|||
/* make sure its aligned correctly */
|
||||
bucketSize = MAXALIGN(bucketSize);
|
||||
|
||||
/*
|
||||
* tmpIndex is the shmem offset into the first bucket of the array.
|
||||
*/
|
||||
tmpBucket = (ELEMENT *)
|
||||
hashp->alloc((unsigned long) BUCKET_ALLOC_INCR * bucketSize);
|
||||
|
||||
if (!tmpBucket)
|
||||
return 0;
|
||||
|
||||
/* tmpIndex is the shmem offset into the first bucket of the array */
|
||||
tmpIndex = MAKE_HASHOFFSET(hashp, tmpBucket);
|
||||
|
||||
/* set the freebucket list to point to the first bucket */
|
||||
|
|
|
|||
Loading…
Reference in New Issue