diff options
Diffstat (limited to 'src/backend/access/hash/hashpage.c')
| -rw-r--r-- | src/backend/access/hash/hashpage.c | 114 |
1 files changed, 60 insertions, 54 deletions
diff --git a/src/backend/access/hash/hashpage.c b/src/backend/access/hash/hashpage.c index 787bb9bf621..d3088f50cef 100644 --- a/src/backend/access/hash/hashpage.c +++ b/src/backend/access/hash/hashpage.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/access/hash/hashpage.c,v 1.45 2004/08/29 04:12:18 momjian Exp $ + * $PostgreSQL: pgsql/src/backend/access/hash/hashpage.c,v 1.46 2004/08/29 05:06:40 momjian Exp $ * * NOTES * Postgres hash pages look like ordinary relation pages. The opaque @@ -35,11 +35,11 @@ static void _hash_splitbucket(Relation rel, Buffer metabuf, - Bucket obucket, Bucket nbucket, - BlockNumber start_oblkno, - BlockNumber start_nblkno, - uint32 maxbucket, - uint32 highmask, uint32 lowmask); + Bucket obucket, Bucket nbucket, + BlockNumber start_oblkno, + BlockNumber start_nblkno, + uint32 maxbucket, + uint32 highmask, uint32 lowmask); /* @@ -47,7 +47,7 @@ static void _hash_splitbucket(Relation rel, Buffer metabuf, * of the locking rules). However, we can skip taking lmgr locks when the * index is local to the current backend (ie, either temp or new in the * current transaction). No one else can see it, so there's no reason to - * take locks. We still take buffer-level locks, but not lmgr locks. + * take locks. We still take buffer-level locks, but not lmgr locks. */ #define USELOCKING(rel) (!RELATION_IS_LOCAL(rel)) @@ -239,13 +239,13 @@ _hash_metapinit(Relation rel) RelationGetRelationName(rel)); /* - * Determine the target fill factor (tuples per bucket) for this index. - * The idea is to make the fill factor correspond to pages about 3/4ths - * full. We can compute it exactly if the index datatype is fixed-width, - * but for var-width there's some guessing involved. + * Determine the target fill factor (tuples per bucket) for this + * index. The idea is to make the fill factor correspond to pages + * about 3/4ths full. We can compute it exactly if the index datatype + * is fixed-width, but for var-width there's some guessing involved. */ data_width = get_typavgwidth(RelationGetDescr(rel)->attrs[0]->atttypid, - RelationGetDescr(rel)->attrs[0]->atttypmod); + RelationGetDescr(rel)->attrs[0]->atttypmod); item_width = MAXALIGN(sizeof(HashItemData)) + MAXALIGN(data_width) + sizeof(ItemIdData); /* include the line pointer */ ffactor = (BLCKSZ * 3 / 4) / item_width; @@ -288,8 +288,9 @@ _hash_metapinit(Relation rel) metap->hashm_procid = index_getprocid(rel, 1, HASHPROC); /* - * We initialize the index with two buckets, 0 and 1, occupying physical - * blocks 1 and 2. The first freespace bitmap page is in block 3. + * We initialize the index with two buckets, 0 and 1, occupying + * physical blocks 1 and 2. The first freespace bitmap page is in + * block 3. */ metap->hashm_maxbucket = metap->hashm_lowmask = 1; /* nbuckets - 1 */ metap->hashm_highmask = 3; /* (nbuckets << 1) - 1 */ @@ -297,7 +298,7 @@ _hash_metapinit(Relation rel) MemSet((char *) metap->hashm_spares, 0, sizeof(metap->hashm_spares)); MemSet((char *) metap->hashm_mapp, 0, sizeof(metap->hashm_mapp)); - metap->hashm_spares[1] = 1; /* the first bitmap page is only spare */ + metap->hashm_spares[1] = 1; /* the first bitmap page is only spare */ metap->hashm_ovflpoint = 1; metap->hashm_firstfree = 0; @@ -319,8 +320,8 @@ _hash_metapinit(Relation rel) } /* - * Initialize first bitmap page. Can't do this until we - * create the first two buckets, else smgr will complain. + * Initialize first bitmap page. Can't do this until we create the + * first two buckets, else smgr will complain. */ _hash_initbitmap(rel, metap, 3); @@ -362,17 +363,18 @@ _hash_expandtable(Relation rel, Buffer metabuf) uint32 lowmask; /* - * Obtain the page-zero lock to assert the right to begin a split - * (see README). + * Obtain the page-zero lock to assert the right to begin a split (see + * README). * * Note: deadlock should be impossible here. Our own backend could only - * be holding bucket sharelocks due to stopped indexscans; those will not - * block other holders of the page-zero lock, who are only interested in - * acquiring bucket sharelocks themselves. Exclusive bucket locks are - * only taken here and in hashbulkdelete, and neither of these operations - * needs any additional locks to complete. (If, due to some flaw in this - * reasoning, we manage to deadlock anyway, it's okay to error out; the - * index will be left in a consistent state.) + * be holding bucket sharelocks due to stopped indexscans; those will + * not block other holders of the page-zero lock, who are only + * interested in acquiring bucket sharelocks themselves. Exclusive + * bucket locks are only taken here and in hashbulkdelete, and neither + * of these operations needs any additional locks to complete. (If, + * due to some flaw in this reasoning, we manage to deadlock anyway, + * it's okay to error out; the index will be left in a consistent + * state.) */ _hash_getlock(rel, 0, HASH_EXCLUSIVE); @@ -383,8 +385,8 @@ _hash_expandtable(Relation rel, Buffer metabuf) _hash_checkpage(rel, (Page) metap, LH_META_PAGE); /* - * Check to see if split is still needed; someone else might have already - * done one while we waited for the lock. + * Check to see if split is still needed; someone else might have + * already done one while we waited for the lock. * * Make sure this stays in sync with_hash_doinsert() */ @@ -394,16 +396,16 @@ _hash_expandtable(Relation rel, Buffer metabuf) /* * Determine which bucket is to be split, and attempt to lock the old - * bucket. If we can't get the lock, give up. + * bucket. If we can't get the lock, give up. * * The lock protects us against other backends, but not against our own * backend. Must check for active scans separately. * - * Ideally we would lock the new bucket too before proceeding, but if - * we are about to cross a splitpoint then the BUCKET_TO_BLKNO mapping + * Ideally we would lock the new bucket too before proceeding, but if we + * are about to cross a splitpoint then the BUCKET_TO_BLKNO mapping * isn't correct yet. For simplicity we update the metapage first and - * then lock. This should be okay because no one else should be trying - * to lock the new bucket yet... + * then lock. This should be okay because no one else should be + * trying to lock the new bucket yet... */ new_bucket = metap->hashm_maxbucket + 1; old_bucket = (new_bucket & metap->hashm_lowmask); @@ -417,7 +419,8 @@ _hash_expandtable(Relation rel, Buffer metabuf) goto fail; /* - * Okay to proceed with split. Update the metapage bucket mapping info. + * Okay to proceed with split. Update the metapage bucket mapping + * info. */ metap->hashm_maxbucket = new_bucket; @@ -431,11 +434,11 @@ _hash_expandtable(Relation rel, Buffer metabuf) /* * If the split point is increasing (hashm_maxbucket's log base 2 * increases), we need to adjust the hashm_spares[] array and - * hashm_ovflpoint so that future overflow pages will be created beyond - * this new batch of bucket pages. + * hashm_ovflpoint so that future overflow pages will be created + * beyond this new batch of bucket pages. * - * XXX should initialize new bucket pages to prevent out-of-order - * page creation? Don't wanna do it right here though. + * XXX should initialize new bucket pages to prevent out-of-order page + * creation? Don't wanna do it right here though. */ spare_ndx = _hash_log2(metap->hashm_maxbucket + 1); if (spare_ndx > metap->hashm_ovflpoint) @@ -456,9 +459,10 @@ _hash_expandtable(Relation rel, Buffer metabuf) /* * Copy bucket mapping info now; this saves re-accessing the meta page * inside _hash_splitbucket's inner loop. Note that once we drop the - * split lock, other splits could begin, so these values might be out of - * date before _hash_splitbucket finishes. That's okay, since all it - * needs is to tell which of these two buckets to map hashkeys into. + * split lock, other splits could begin, so these values might be out + * of date before _hash_splitbucket finishes. That's okay, since all + * it needs is to tell which of these two buckets to map hashkeys + * into. */ maxbucket = metap->hashm_maxbucket; highmask = metap->hashm_highmask; @@ -539,8 +543,8 @@ _hash_splitbucket(Relation rel, /* * It should be okay to simultaneously write-lock pages from each - * bucket, since no one else can be trying to acquire buffer lock - * on pages of either bucket. + * bucket, since no one else can be trying to acquire buffer lock on + * pages of either bucket. */ oblkno = start_oblkno; nblkno = start_nblkno; @@ -562,9 +566,9 @@ _hash_splitbucket(Relation rel, nopaque->hasho_filler = HASHO_FILL; /* - * Partition the tuples in the old bucket between the old bucket and the - * new bucket, advancing along the old bucket's overflow bucket chain - * and adding overflow pages to the new bucket as needed. + * Partition the tuples in the old bucket between the old bucket and + * the new bucket, advancing along the old bucket's overflow bucket + * chain and adding overflow pages to the new bucket as needed. */ ooffnum = FirstOffsetNumber; omaxoffnum = PageGetMaxOffsetNumber(opage); @@ -582,9 +586,10 @@ _hash_splitbucket(Relation rel, oblkno = oopaque->hasho_nextblkno; if (!BlockNumberIsValid(oblkno)) break; + /* - * we ran out of tuples on this particular page, but we - * have more overflow pages; advance to next page. + * we ran out of tuples on this particular page, but we have + * more overflow pages; advance to next page. */ _hash_wrtbuf(rel, obuf); @@ -600,8 +605,8 @@ _hash_splitbucket(Relation rel, /* * Re-hash the tuple to determine which bucket it now belongs in. * - * It is annoying to call the hash function while holding locks, - * but releasing and relocking the page for each tuple is unappealing + * It is annoying to call the hash function while holding locks, but + * releasing and relocking the page for each tuple is unappealing * too. */ hitem = (HashItem) PageGetItem(opage, PageGetItemId(opage, ooffnum)); @@ -666,10 +671,11 @@ _hash_splitbucket(Relation rel, } /* - * We're at the end of the old bucket chain, so we're done partitioning - * the tuples. Before quitting, call _hash_squeezebucket to ensure the - * tuples remaining in the old bucket (including the overflow pages) are - * packed as tightly as possible. The new bucket is already tight. + * We're at the end of the old bucket chain, so we're done + * partitioning the tuples. Before quitting, call _hash_squeezebucket + * to ensure the tuples remaining in the old bucket (including the + * overflow pages) are packed as tightly as possible. The new bucket + * is already tight. */ _hash_wrtbuf(rel, obuf); _hash_wrtbuf(rel, nbuf); |