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Commit21a3cf4

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hash: Refactor and clean up bucket split code.
As with commit30df93f and commitb0f18cb, the goal here is to move allof the related page modifications to a single section of code, inpreparation for adding write-ahead logging.Amit Kapila, with slight changes by me. The larger patch series ofwhich this is a part has been reviewed and tested by Álvaro Herrera,Ashutosh Sharma, Mark Kirkwood, Jeff Janes, and Jesper Pedersen.
1 parent123ccbe commit21a3cf4

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1 file changed

+67
-93
lines changed

1 file changed

+67
-93
lines changed

‎src/backend/access/hash/hashpage.c

Lines changed: 67 additions & 93 deletions
Original file line numberDiff line numberDiff line change
@@ -40,12 +40,9 @@ static void _hash_splitbucket(Relation rel, Buffer metabuf,
4040
Bucketobucket,Bucketnbucket,
4141
Bufferobuf,
4242
Buffernbuf,
43+
HTAB*htab,
4344
uint32maxbucket,
4445
uint32highmask,uint32lowmask);
45-
staticvoid_hash_splitbucket_guts(Relationrel,Buffermetabuf,
46-
Bucketobucket,Bucketnbucket,Bufferobuf,
47-
Buffernbuf,HTAB*htab,uint32maxbucket,
48-
uint32highmask,uint32lowmask);
4946

5047

5148
/*
@@ -497,7 +494,9 @@ _hash_expandtable(Relation rel, Buffer metabuf)
497494
Bufferbuf_nblkno;
498495
Bufferbuf_oblkno;
499496
Pageopage;
497+
Pagenpage;
500498
HashPageOpaqueoopaque;
499+
HashPageOpaquenopaque;
501500
uint32maxbucket;
502501
uint32highmask;
503502
uint32lowmask;
@@ -685,18 +684,18 @@ _hash_expandtable(Relation rel, Buffer metabuf)
685684
gotofail;
686685
}
687686

688-
689687
/*
690-
* Okay to proceed with split. Update the metapage bucket mapping info.
691-
*
692-
* Since we are scribbling on the metapage data right in the shared
693-
* buffer, any failure in this next little bit leaves us with a big
688+
* Since we are scribbling on the pages in the shared buffers, establish a
689+
* critical section. Any failure in this next code leaves us with a big
694690
* problem: the metapage is effectively corrupt but could get written back
695691
* to disk. We don't really expect any failure, but just to be sure,
696692
* establish a critical section.
697693
*/
698694
START_CRIT_SECTION();
699695

696+
/*
697+
* Okay to proceed with split. Update the metapage bucket mapping info.
698+
*/
700699
metap->hashm_maxbucket=new_bucket;
701700

702701
if (new_bucket>metap->hashm_highmask)
@@ -718,8 +717,7 @@ _hash_expandtable(Relation rel, Buffer metabuf)
718717
metap->hashm_ovflpoint=spare_ndx;
719718
}
720719

721-
/* Done mucking with metapage */
722-
END_CRIT_SECTION();
720+
MarkBufferDirty(metabuf);
723721

724722
/*
725723
* Copy bucket mapping info now; this saves re-accessing the meta page
@@ -732,16 +730,51 @@ _hash_expandtable(Relation rel, Buffer metabuf)
732730
highmask=metap->hashm_highmask;
733731
lowmask=metap->hashm_lowmask;
734732

735-
/* Write out the metapage and drop lock, but keep pin */
736-
MarkBufferDirty(metabuf);
733+
opage=BufferGetPage(buf_oblkno);
734+
oopaque= (HashPageOpaque)PageGetSpecialPointer(opage);
735+
736+
/*
737+
* Mark the old bucket to indicate that split is in progress. (At
738+
* operation end, we will clear the split-in-progress flag.) Also,
739+
* for a primary bucket page, hasho_prevblkno stores the number of
740+
* buckets that existed as of the last split, so we must update that
741+
* value here.
742+
*/
743+
oopaque->hasho_flag |=LH_BUCKET_BEING_SPLIT;
744+
oopaque->hasho_prevblkno=maxbucket;
745+
746+
MarkBufferDirty(buf_oblkno);
747+
748+
npage=BufferGetPage(buf_nblkno);
749+
750+
/*
751+
* initialize the new bucket's primary page and mark it to indicate that
752+
* split is in progress.
753+
*/
754+
nopaque= (HashPageOpaque)PageGetSpecialPointer(npage);
755+
nopaque->hasho_prevblkno=maxbucket;
756+
nopaque->hasho_nextblkno=InvalidBlockNumber;
757+
nopaque->hasho_bucket=new_bucket;
758+
nopaque->hasho_flag=LH_BUCKET_PAGE |LH_BUCKET_BEING_POPULATED;
759+
nopaque->hasho_page_id=HASHO_PAGE_ID;
760+
761+
MarkBufferDirty(buf_nblkno);
762+
763+
END_CRIT_SECTION();
764+
765+
/* drop lock, but keep pin */
737766
LockBuffer(metabuf,BUFFER_LOCK_UNLOCK);
738767

739768
/* Relocate records to the new bucket */
740769
_hash_splitbucket(rel,metabuf,
741770
old_bucket,new_bucket,
742-
buf_oblkno,buf_nblkno,
771+
buf_oblkno,buf_nblkno,NULL,
743772
maxbucket,highmask,lowmask);
744773

774+
/* all done, now release the locks and pins on primary buckets. */
775+
_hash_relbuf(rel,buf_oblkno);
776+
_hash_relbuf(rel,buf_nblkno);
777+
745778
return;
746779

747780
/* Here if decide not to split or fail to acquire old bucket lock */
@@ -803,10 +836,16 @@ _hash_alloc_buckets(Relation rel, BlockNumber firstblock, uint32 nblocks)
803836
/*
804837
* _hash_splitbucket -- split 'obucket' into 'obucket' and 'nbucket'
805838
*
839+
* This routine is used to partition the tuples between old and new bucket and
840+
* is used to finish the incomplete split operations. To finish the previously
841+
* interrupted split operation, the caller needs to fill htab. If htab is set,
842+
* then we skip the movement of tuples that exists in htab, otherwise NULL
843+
* value of htab indicates movement of all the tuples that belong to the new
844+
* bucket.
845+
*
806846
* We are splitting a bucket that consists of a base bucket page and zero
807847
* or more overflow (bucket chain) pages. We must relocate tuples that
808-
* belong in the new bucket, and compress out any free space in the old
809-
* bucket.
848+
* belong in the new bucket.
810849
*
811850
* The caller must hold cleanup locks on both buckets to ensure that
812851
* no one else is trying to access them (see README).
@@ -832,72 +871,10 @@ _hash_splitbucket(Relation rel,
832871
Bucketnbucket,
833872
Bufferobuf,
834873
Buffernbuf,
874+
HTAB*htab,
835875
uint32maxbucket,
836876
uint32highmask,
837877
uint32lowmask)
838-
{
839-
Pageopage;
840-
Pagenpage;
841-
HashPageOpaqueoopaque;
842-
HashPageOpaquenopaque;
843-
844-
opage=BufferGetPage(obuf);
845-
oopaque= (HashPageOpaque)PageGetSpecialPointer(opage);
846-
847-
/*
848-
* Mark the old bucket to indicate that split is in progress. (At
849-
* operation end, we will clear the split-in-progress flag.) Also,
850-
* for a primary bucket page, hasho_prevblkno stores the number of
851-
* buckets that existed as of the last split, so we must update that
852-
* value here.
853-
*/
854-
oopaque->hasho_flag |=LH_BUCKET_BEING_SPLIT;
855-
oopaque->hasho_prevblkno=maxbucket;
856-
857-
npage=BufferGetPage(nbuf);
858-
859-
/*
860-
* initialize the new bucket's primary page and mark it to indicate that
861-
* split is in progress.
862-
*/
863-
nopaque= (HashPageOpaque)PageGetSpecialPointer(npage);
864-
nopaque->hasho_prevblkno=maxbucket;
865-
nopaque->hasho_nextblkno=InvalidBlockNumber;
866-
nopaque->hasho_bucket=nbucket;
867-
nopaque->hasho_flag=LH_BUCKET_PAGE |LH_BUCKET_BEING_POPULATED;
868-
nopaque->hasho_page_id=HASHO_PAGE_ID;
869-
870-
_hash_splitbucket_guts(rel,metabuf,obucket,
871-
nbucket,obuf,nbuf,NULL,
872-
maxbucket,highmask,lowmask);
873-
874-
/* all done, now release the locks and pins on primary buckets. */
875-
_hash_relbuf(rel,obuf);
876-
_hash_relbuf(rel,nbuf);
877-
}
878-
879-
/*
880-
* _hash_splitbucket_guts -- Helper function to perform the split operation
881-
*
882-
* This routine is used to partition the tuples between old and new bucket and
883-
* to finish incomplete split operations. To finish the previously
884-
* interrupted split operation, caller needs to fill htab. If htab is set, then
885-
* we skip the movement of tuples that exists in htab, otherwise NULL value of
886-
* htab indicates movement of all the tuples that belong to new bucket.
887-
*
888-
* Caller needs to lock and unlock the old and new primary buckets.
889-
*/
890-
staticvoid
891-
_hash_splitbucket_guts(Relationrel,
892-
Buffermetabuf,
893-
Bucketobucket,
894-
Bucketnbucket,
895-
Bufferobuf,
896-
Buffernbuf,
897-
HTAB*htab,
898-
uint32maxbucket,
899-
uint32highmask,
900-
uint32lowmask)
901878
{
902879
Bufferbucket_obuf;
903880
Bufferbucket_nbuf;
@@ -987,6 +964,7 @@ _hash_splitbucket_guts(Relation rel,
987964
{
988965
/* write out nbuf and drop lock, but keep pin */
989966
MarkBufferDirty(nbuf);
967+
/* drop lock, but keep pin */
990968
LockBuffer(nbuf,BUFFER_LOCK_UNLOCK);
991969
/* chain to a new overflow page */
992970
nbuf=_hash_addovflpage(rel,metabuf,nbuf, (nbuf==bucket_nbuf) ? true : false);
@@ -1025,7 +1003,14 @@ _hash_splitbucket_guts(Relation rel,
10251003

10261004
/* Exit loop if no more overflow pages in old bucket */
10271005
if (!BlockNumberIsValid(oblkno))
1006+
{
1007+
MarkBufferDirty(nbuf);
1008+
if (nbuf==bucket_nbuf)
1009+
LockBuffer(nbuf,BUFFER_LOCK_UNLOCK);
1010+
else
1011+
_hash_relbuf(rel,nbuf);
10281012
break;
1013+
}
10291014

10301015
/* Else, advance to next old page */
10311016
obuf=_hash_getbuf(rel,oblkno,HASH_READ,LH_OVERFLOW_PAGE);
@@ -1041,17 +1026,6 @@ _hash_splitbucket_guts(Relation rel,
10411026
* To avoid deadlocks due to locking order of buckets, first lock the old
10421027
* bucket and then the new bucket.
10431028
*/
1044-
if (nbuf==bucket_nbuf)
1045-
{
1046-
MarkBufferDirty(bucket_nbuf);
1047-
LockBuffer(bucket_nbuf,BUFFER_LOCK_UNLOCK);
1048-
}
1049-
else
1050-
{
1051-
MarkBufferDirty(nbuf);
1052-
_hash_relbuf(rel,nbuf);
1053-
}
1054-
10551029
LockBuffer(bucket_obuf,BUFFER_LOCK_EXCLUSIVE);
10561030
opage=BufferGetPage(bucket_obuf);
10571031
oopaque= (HashPageOpaque)PageGetSpecialPointer(opage);
@@ -1192,9 +1166,9 @@ _hash_finish_split(Relation rel, Buffer metabuf, Buffer obuf, Bucket obucket,
11921166
npageopaque= (HashPageOpaque)PageGetSpecialPointer(npage);
11931167
nbucket=npageopaque->hasho_bucket;
11941168

1195-
_hash_splitbucket_guts(rel,metabuf,obucket,
1196-
nbucket,obuf,bucket_nbuf,tidhtab,
1197-
maxbucket,highmask,lowmask);
1169+
_hash_splitbucket(rel,metabuf,obucket,
1170+
nbucket,obuf,bucket_nbuf,tidhtab,
1171+
maxbucket,highmask,lowmask);
11981172

11991173
_hash_relbuf(rel,bucket_nbuf);
12001174
LockBuffer(obuf,BUFFER_LOCK_UNLOCK);

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