diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/utils/hash/dynahash.c | 27 |
1 files changed, 19 insertions, 8 deletions
diff --git a/src/backend/utils/hash/dynahash.c b/src/backend/utils/hash/dynahash.c index 1d473218a77..5454befe152 100644 --- a/src/backend/utils/hash/dynahash.c +++ b/src/backend/utils/hash/dynahash.c @@ -1022,6 +1022,7 @@ hash_update_hash_key(HTAB *hashp, uint32 newhashvalue; Size keysize; uint32 bucket; + uint32 newbucket; long segment_num; long segment_ndx; HASHSEGMENT segp; @@ -1078,10 +1079,10 @@ hash_update_hash_key(HTAB *hashp, */ newhashvalue = hashp->hash(newKeyPtr, hashp->keysize); - bucket = calc_bucket(hctl, newhashvalue); + newbucket = calc_bucket(hctl, newhashvalue); - segment_num = bucket >> hashp->sshift; - segment_ndx = MOD(bucket, hashp->ssize); + segment_num = newbucket >> hashp->sshift; + segment_ndx = MOD(newbucket, hashp->ssize); segp = hashp->dir[segment_num]; @@ -1115,12 +1116,22 @@ hash_update_hash_key(HTAB *hashp, currBucket = existingElement; - /* OK to remove record from old hash bucket's chain. */ - *oldPrevPtr = currBucket->link; + /* + * If old and new hash values belong to the same bucket, we need not + * change any chain links, and indeed should not since this simplistic + * update will corrupt the list if currBucket is the last element. (We + * cannot fall out earlier, however, since we need to scan the bucket to + * check for duplicate keys.) + */ + if (bucket != newbucket) + { + /* OK to remove record from old hash bucket's chain. */ + *oldPrevPtr = currBucket->link; - /* link into new hashbucket chain */ - *prevBucketPtr = currBucket; - currBucket->link = NULL; + /* link into new hashbucket chain */ + *prevBucketPtr = currBucket; + currBucket->link = NULL; + } /* copy new key into record */ currBucket->hashvalue = newhashvalue; |