* hashpage.c
* Hash table page management code for the Postgres hash access method
*
- * Portions Copyright (c) 1996-2011, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* 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))
/*
* _hash_getlock() -- Acquire an lmgr lock.
*
- * 'whichlock' should be zero to acquire the split-control lock, or the
- * block number of a bucket's primary bucket page to acquire the per-bucket
- * lock. (See README for details of the use of these locks.)
+ * 'whichlock' should the block number of a bucket's primary bucket page to
+ * acquire the per-bucket lock. (See README for details of the use of these
+ * locks.)
*
* 'access' must be HASH_SHARE or HASH_EXCLUSIVE.
*/
*
* This must be used only to fetch pages that are known to be before
* the index's filesystem EOF, but are to be filled from scratch.
- * _hash_pageinit() is applied automatically. Otherwise it has
+ * _hash_pageinit() is applied automatically. Otherwise it has
* effects similar to _hash_getbuf() with access = HASH_WRITE.
*
* When this routine returns, a write lock is set on the
/*
* Determine the target fill factor (in tuples per bucket) for this index.
* The idea is to make the fill factor correspond to pages about as full
- * as the user-settable fillfactor parameter says. We can compute it
+ * as the user-settable fillfactor parameter says. We can compute it
* exactly since the index datatype (i.e. uint32 hash key) is fixed-width.
*/
data_width = sizeof(uint32);
/*
* We initialize the metapage, the first N bucket pages, and the first
* bitmap page in sequence, using _hash_getnewbuf to cause smgrextend()
- * calls to occur. This ensures that the smgr level has the right idea of
+ * calls to occur. This ensures that the smgr level has the right idea of
* the physical index length.
*/
metabuf = _hash_getnewbuf(rel, HASH_METAPAGE, forkNum);
uint32 lowmask;
/*
- * 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.)
+ * Write-lock the meta page. It used to be necessary to acquire a
+ * heavyweight lock to begin a split, but that is no longer required.
*/
- _hash_getlock(rel, 0, HASH_EXCLUSIVE);
-
- /* Write-lock the meta page */
_hash_chgbufaccess(rel, metabuf, HASH_NOLOCK, HASH_WRITE);
_hash_checkpage(rel, metabuf, LH_META_PAGE);
/*
* 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.
}
/*
- * Okay to proceed with split. Update the metapage bucket mapping info.
+ * Okay to proceed with split. Update the metapage bucket mapping info.
*
* Since we are scribbling on the metapage data right in the shared
* buffer, any failure in this next little bit leaves us with a big
* 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
+ * 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;
/* Write out the metapage and drop lock, but keep pin */
_hash_chgbufaccess(rel, metabuf, HASH_WRITE, HASH_NOLOCK);
- /* Release split lock; okay for other splits to occur now */
- _hash_droplock(rel, 0, HASH_EXCLUSIVE);
-
/* Relocate records to the new bucket */
_hash_splitbucket(rel, metabuf, old_bucket, new_bucket,
start_oblkno, start_nblkno,
/* We didn't write the metapage, so just drop lock */
_hash_chgbufaccess(rel, metabuf, HASH_READ, HASH_NOLOCK);
-
- /* Release split lock */
- _hash_droplock(rel, 0, HASH_EXCLUSIVE);
}
/*
* 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
+ * 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.
*/
projects / postgresql / blobdiff