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Commitcc5ef90

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Refactor initial hash lookup in dynahash.c
The same pattern is used three times in dynahash.c to retrieve a bucketnumber and a hash bucket from a hash value. This has popped up whilediscussing improvements for the type cache, where this piece ofrefactoring would become useful.Note that hash_search_with_hash_value() does not need the bucket number,just the hash bucket.Author: Teodor SigaevReviewed-by: Aleksander Alekseev, Michael PaquierDiscussion:https://postgr.es/m/5812a6e5-68ae-4d84-9d85-b443176966a1@sigaev.ru
1 parent4169850 commitcc5ef90

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+33
-42
lines changed

1 file changed

+33
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‎src/backend/utils/hash/dynahash.c

Lines changed: 33 additions & 42 deletions
Original file line numberDiff line numberDiff line change
@@ -273,6 +273,8 @@ static void hdefault(HTAB *hashp);
273273
staticintchoose_nelem_alloc(Sizeentrysize);
274274
staticboolinit_htab(HTAB*hashp,longnelem);
275275
staticvoidhash_corrupted(HTAB*hashp);
276+
staticuint32hash_initial_lookup(HTAB*hashp,uint32hashvalue,
277+
HASHBUCKET**bucketptr);
276278
staticlongnext_pow2_long(longnum);
277279
staticintnext_pow2_int(longnum);
278280
staticvoidregister_seq_scan(HTAB*hashp);
@@ -972,10 +974,6 @@ hash_search_with_hash_value(HTAB *hashp,
972974
HASHHDR*hctl=hashp->hctl;
973975
intfreelist_idx=FREELIST_IDX(hctl,hashvalue);
974976
Sizekeysize;
975-
uint32bucket;
976-
longsegment_num;
977-
longsegment_ndx;
978-
HASHSEGMENTsegp;
979977
HASHBUCKETcurrBucket;
980978
HASHBUCKET*prevBucketPtr;
981979
HashCompareFuncmatch;
@@ -1008,17 +1006,7 @@ hash_search_with_hash_value(HTAB *hashp,
10081006
/*
10091007
* Do the initial lookup
10101008
*/
1011-
bucket=calc_bucket(hctl,hashvalue);
1012-
1013-
segment_num=bucket >>hashp->sshift;
1014-
segment_ndx=MOD(bucket,hashp->ssize);
1015-
1016-
segp=hashp->dir[segment_num];
1017-
1018-
if (segp==NULL)
1019-
hash_corrupted(hashp);
1020-
1021-
prevBucketPtr=&segp[segment_ndx];
1009+
(void)hash_initial_lookup(hashp,hashvalue,&prevBucketPtr);
10221010
currBucket=*prevBucketPtr;
10231011

10241012
/*
@@ -1159,14 +1147,10 @@ hash_update_hash_key(HTAB *hashp,
11591147
constvoid*newKeyPtr)
11601148
{
11611149
HASHELEMENT*existingElement=ELEMENT_FROM_KEY(existingEntry);
1162-
HASHHDR*hctl=hashp->hctl;
11631150
uint32newhashvalue;
11641151
Sizekeysize;
11651152
uint32bucket;
11661153
uint32newbucket;
1167-
longsegment_num;
1168-
longsegment_ndx;
1169-
HASHSEGMENTsegp;
11701154
HASHBUCKETcurrBucket;
11711155
HASHBUCKET*prevBucketPtr;
11721156
HASHBUCKET*oldPrevPtr;
@@ -1187,17 +1171,8 @@ hash_update_hash_key(HTAB *hashp,
11871171
* this to be able to unlink it from its hash chain, but as a side benefit
11881172
* we can verify the validity of the passed existingEntry pointer.
11891173
*/
1190-
bucket=calc_bucket(hctl,existingElement->hashvalue);
1191-
1192-
segment_num=bucket >>hashp->sshift;
1193-
segment_ndx=MOD(bucket,hashp->ssize);
1194-
1195-
segp=hashp->dir[segment_num];
1196-
1197-
if (segp==NULL)
1198-
hash_corrupted(hashp);
1199-
1200-
prevBucketPtr=&segp[segment_ndx];
1174+
bucket=hash_initial_lookup(hashp,existingElement->hashvalue,
1175+
&prevBucketPtr);
12011176
currBucket=*prevBucketPtr;
12021177

12031178
while (currBucket!=NULL)
@@ -1219,18 +1194,7 @@ hash_update_hash_key(HTAB *hashp,
12191194
* chain we want to put the entry into.
12201195
*/
12211196
newhashvalue=hashp->hash(newKeyPtr,hashp->keysize);
1222-
1223-
newbucket=calc_bucket(hctl,newhashvalue);
1224-
1225-
segment_num=newbucket >>hashp->sshift;
1226-
segment_ndx=MOD(newbucket,hashp->ssize);
1227-
1228-
segp=hashp->dir[segment_num];
1229-
1230-
if (segp==NULL)
1231-
hash_corrupted(hashp);
1232-
1233-
prevBucketPtr=&segp[segment_ndx];
1197+
newbucket=hash_initial_lookup(hashp,newhashvalue,&prevBucketPtr);
12341198
currBucket=*prevBucketPtr;
12351199

12361200
/*
@@ -1741,6 +1705,33 @@ element_alloc(HTAB *hashp, int nelem, int freelist_idx)
17411705
return true;
17421706
}
17431707

1708+
/*
1709+
* Do initial lookup of a bucket for the given hash value, retrieving its
1710+
* bucket number and its hash bucket.
1711+
*/
1712+
staticinlineuint32
1713+
hash_initial_lookup(HTAB*hashp,uint32hashvalue,HASHBUCKET**bucketptr)
1714+
{
1715+
HASHHDR*hctl=hashp->hctl;
1716+
HASHSEGMENTsegp;
1717+
longsegment_num;
1718+
longsegment_ndx;
1719+
uint32bucket;
1720+
1721+
bucket=calc_bucket(hctl,hashvalue);
1722+
1723+
segment_num=bucket >>hashp->sshift;
1724+
segment_ndx=MOD(bucket,hashp->ssize);
1725+
1726+
segp=hashp->dir[segment_num];
1727+
1728+
if (segp==NULL)
1729+
hash_corrupted(hashp);
1730+
1731+
*bucketptr=&segp[segment_ndx];
1732+
returnbucket;
1733+
}
1734+
17441735
/* complain when we have detected a corrupted hashtable */
17451736
staticvoid
17461737
hash_corrupted(HTAB*hashp)

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