* hashpage.c
* Hash table page management code for the Postgres hash access method
*
- * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/access/hash/hashpage.c,v 1.54 2005/11/22 18:17:05 momjian Exp $
+ * src/backend/access/hash/hashpage.c
*
* NOTES
* Postgres hash pages look like ordinary relation pages. The opaque
*/
#include "postgres.h"
-#include "access/genam.h"
#include "access/hash.h"
#include "miscadmin.h"
#include "storage/lmgr.h"
-#include "utils/lsyscache.h"
+#include "storage/smgr.h"
+static bool _hash_alloc_buckets(Relation rel, BlockNumber firstblock,
+ uint32 nblocks);
static void _hash_splitbucket(Relation rel, Buffer metabuf,
Bucket obucket, Bucket nbucket,
BlockNumber start_oblkno,
* 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.
*/
* _hash_getbuf() -- Get a buffer by block number for read or write.
*
* 'access' must be HASH_READ, HASH_WRITE, or HASH_NOLOCK.
+ * 'flags' is a bitwise OR of the allowed page types.
+ *
+ * This must be used only to fetch pages that are expected to be valid
+ * already. _hash_checkpage() is applied using the given flags.
*
* When this routine returns, the appropriate lock is set on the
* requested buffer and its reference count has been incremented
* (ie, the buffer is "locked and pinned").
*
- * XXX P_NEW is not used because, unlike the tree structures, we
- * need the bucket blocks to be at certain block numbers.
- *
- * All call sites should call either _hash_pageinit or _hash_checkpage
- * on the returned page, depending on whether the block is expected
- * to be new or not.
+ * P_NEW is disallowed because this routine can only be used
+ * to access pages that are known to be before the filesystem EOF.
+ * Extending the index should be done with _hash_getnewbuf.
*/
Buffer
-_hash_getbuf(Relation rel, BlockNumber blkno, int access)
+_hash_getbuf(Relation rel, BlockNumber blkno, int access, int flags)
{
Buffer buf;
LockBuffer(buf, access);
/* ref count and lock type are correct */
+
+ _hash_checkpage(rel, buf, flags);
+
+ return buf;
+}
+
+/*
+ * _hash_getinitbuf() -- Get and initialize a buffer by block number.
+ *
+ * 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
+ * effects similar to _hash_getbuf() with access = HASH_WRITE.
+ *
+ * When this routine returns, a write lock is set on the
+ * requested buffer and its reference count has been incremented
+ * (ie, the buffer is "locked and pinned").
+ *
+ * P_NEW is disallowed because this routine can only be used
+ * to access pages that are known to be before the filesystem EOF.
+ * Extending the index should be done with _hash_getnewbuf.
+ */
+Buffer
+_hash_getinitbuf(Relation rel, BlockNumber blkno)
+{
+ Buffer buf;
+
+ if (blkno == P_NEW)
+ elog(ERROR, "hash AM does not use P_NEW");
+
+ buf = ReadBufferExtended(rel, MAIN_FORKNUM, blkno, RBM_ZERO, NULL);
+
+ LockBuffer(buf, HASH_WRITE);
+
+ /* ref count and lock type are correct */
+
+ /* initialize the page */
+ _hash_pageinit(BufferGetPage(buf), BufferGetPageSize(buf));
+
+ return buf;
+}
+
+/*
+ * _hash_getnewbuf() -- Get a new page at the end of the index.
+ *
+ * This has the same API as _hash_getinitbuf, except that we are adding
+ * a page to the index, and hence expect the page to be past the
+ * logical EOF. (However, we have to support the case where it isn't,
+ * since a prior try might have crashed after extending the filesystem
+ * EOF but before updating the metapage to reflect the added page.)
+ *
+ * It is caller's responsibility to ensure that only one process can
+ * extend the index at a time.
+ */
+Buffer
+_hash_getnewbuf(Relation rel, BlockNumber blkno, ForkNumber forkNum)
+{
+ BlockNumber nblocks = RelationGetNumberOfBlocksInFork(rel, forkNum);
+ Buffer buf;
+
+ if (blkno == P_NEW)
+ elog(ERROR, "hash AM does not use P_NEW");
+ if (blkno > nblocks)
+ elog(ERROR, "access to noncontiguous page in hash index \"%s\"",
+ RelationGetRelationName(rel));
+
+ /* smgr insists we use P_NEW to extend the relation */
+ if (blkno == nblocks)
+ {
+ buf = ReadBufferExtended(rel, forkNum, P_NEW, RBM_NORMAL, NULL);
+ if (BufferGetBlockNumber(buf) != blkno)
+ elog(ERROR, "unexpected hash relation size: %u, should be %u",
+ BufferGetBlockNumber(buf), blkno);
+ }
+ else
+ buf = ReadBufferExtended(rel, forkNum, blkno, RBM_ZERO, NULL);
+
+ LockBuffer(buf, HASH_WRITE);
+
+ /* ref count and lock type are correct */
+
+ /* initialize the page */
+ _hash_pageinit(BufferGetPage(buf), BufferGetPageSize(buf));
+
+ return buf;
+}
+
+/*
+ * _hash_getbuf_with_strategy() -- Get a buffer with nondefault strategy.
+ *
+ * This is identical to _hash_getbuf() but also allows a buffer access
+ * strategy to be specified. We use this for VACUUM operations.
+ */
+Buffer
+_hash_getbuf_with_strategy(Relation rel, BlockNumber blkno,
+ int access, int flags,
+ BufferAccessStrategy bstrategy)
+{
+ Buffer buf;
+
+ if (blkno == P_NEW)
+ elog(ERROR, "hash AM does not use P_NEW");
+
+ buf = ReadBufferExtended(rel, MAIN_FORKNUM, blkno, RBM_NORMAL, bstrategy);
+
+ if (access != HASH_NOLOCK)
+ LockBuffer(buf, access);
+
+ /* ref count and lock type are correct */
+
+ _hash_checkpage(rel, buf, flags);
+
return buf;
}
/*
* _hash_relbuf() -- release a locked buffer.
*
- * Lock and pin (refcount) are both dropped. Note that either read or
- * write lock can be dropped this way, but if we modified the buffer,
- * this is NOT the right way to release a write lock.
+ * Lock and pin (refcount) are both dropped.
*/
void
_hash_relbuf(Relation rel, Buffer buf)
{
- LockBuffer(buf, BUFFER_LOCK_UNLOCK);
- ReleaseBuffer(buf);
+ UnlockReleaseBuffer(buf);
}
/*
* _hash_dropbuf() -- release an unlocked buffer.
*
- * This is used to unpin a buffer on which we hold no lock. It is assumed
- * that the buffer is not dirty.
+ * This is used to unpin a buffer on which we hold no lock.
*/
void
_hash_dropbuf(Relation rel, Buffer buf)
* for it. It is an error to call _hash_wrtbuf() without a write lock
* and a pin on the buffer.
*
- * NOTE: actually, the buffer manager just marks the shared buffer page
- * dirty here; the real I/O happens later. This is okay since we are not
- * relying on write ordering anyway. The WAL mechanism is responsible for
- * guaranteeing correctness after a crash.
+ * NOTE: this routine should go away when/if hash indexes are WAL-ified.
+ * The correct sequence of operations is to mark the buffer dirty, then
+ * write the WAL record, then release the lock and pin; so marking dirty
+ * can't be combined with releasing.
*/
void
_hash_wrtbuf(Relation rel, Buffer buf)
{
- LockBuffer(buf, BUFFER_LOCK_UNLOCK);
- WriteBuffer(buf);
-}
-
-/*
- * _hash_wrtnorelbuf() -- write a hash page to disk, but do not release
- * our reference or lock.
- *
- * It is an error to call _hash_wrtnorelbuf() without a write lock
- * and a pin on the buffer.
- *
- * See above NOTE.
- */
-void
-_hash_wrtnorelbuf(Relation rel, Buffer buf)
-{
- WriteNoReleaseBuffer(buf);
+ MarkBufferDirty(buf);
+ UnlockReleaseBuffer(buf);
}
/*
int from_access,
int to_access)
{
+ if (from_access == HASH_WRITE)
+ MarkBufferDirty(buf);
if (from_access != HASH_NOLOCK)
LockBuffer(buf, BUFFER_LOCK_UNLOCK);
- if (from_access == HASH_WRITE)
- WriteNoReleaseBuffer(buf);
-
if (to_access != HASH_NOLOCK)
LockBuffer(buf, to_access);
}
/*
* _hash_metapinit() -- Initialize the metadata page of a hash index,
- * the two buckets that we begin with and the initial
- * bitmap page.
+ * the initial buckets, and the initial bitmap page.
+ *
+ * The initial number of buckets is dependent on num_tuples, an estimate
+ * of the number of tuples to be loaded into the index initially. The
+ * chosen number of buckets is returned.
*
* We are fairly cavalier about locking here, since we know that no one else
* could be accessing this index. In particular the rule about not holding
* multiple buffer locks is ignored.
*/
-void
-_hash_metapinit(Relation rel)
+uint32
+_hash_metapinit(Relation rel, double num_tuples, ForkNumber forkNum)
{
HashMetaPage metap;
HashPageOpaque pageopaque;
int32 data_width;
int32 item_width;
int32 ffactor;
- uint16 i;
+ double dnumbuckets;
+ uint32 num_buckets;
+ uint32 log2_num_buckets;
+ uint32 i;
/* safety check */
- if (RelationGetNumberOfBlocks(rel) != 0)
+ if (RelationGetNumberOfBlocksInFork(rel, forkNum) != 0)
elog(ERROR, "cannot initialize non-empty hash index \"%s\"",
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 (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
+ * exactly since the index datatype (i.e. uint32 hash key) is fixed-width.
*/
- data_width = get_typavgwidth(RelationGetDescr(rel)->attrs[0]->atttypid,
- RelationGetDescr(rel)->attrs[0]->atttypmod);
- item_width = MAXALIGN(sizeof(HashItemData)) + MAXALIGN(data_width) +
+ data_width = sizeof(uint32);
+ item_width = MAXALIGN(sizeof(IndexTupleData)) + MAXALIGN(data_width) +
sizeof(ItemIdData); /* include the line pointer */
- ffactor = (BLCKSZ * 3 / 4) / item_width;
+ ffactor = RelationGetTargetPageUsage(rel, HASH_DEFAULT_FILLFACTOR) / item_width;
/* keep to a sane range */
if (ffactor < 10)
ffactor = 10;
- metabuf = _hash_getbuf(rel, HASH_METAPAGE, HASH_WRITE);
+ /*
+ * Choose the number of initial bucket pages to match the fill factor
+ * given the estimated number of tuples. We round up the result to the
+ * next power of 2, however, and always force at least 2 bucket pages. The
+ * upper limit is determined by considerations explained in
+ * _hash_expandtable().
+ */
+ dnumbuckets = num_tuples / ffactor;
+ if (dnumbuckets <= 2.0)
+ num_buckets = 2;
+ else if (dnumbuckets >= (double) 0x40000000)
+ num_buckets = 0x40000000;
+ else
+ num_buckets = ((uint32) 1) << _hash_log2((uint32) dnumbuckets);
+
+ log2_num_buckets = _hash_log2(num_buckets);
+ Assert(num_buckets == (((uint32) 1) << log2_num_buckets));
+ Assert(log2_num_buckets < HASH_MAX_SPLITPOINTS);
+
+ /*
+ * 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
+ * the physical index length.
+ */
+ metabuf = _hash_getnewbuf(rel, HASH_METAPAGE, forkNum);
pg = BufferGetPage(metabuf);
- _hash_pageinit(pg, BufferGetPageSize(metabuf));
pageopaque = (HashPageOpaque) PageGetSpecialPointer(pg);
pageopaque->hasho_prevblkno = InvalidBlockNumber;
pageopaque->hasho_nextblkno = InvalidBlockNumber;
pageopaque->hasho_bucket = -1;
pageopaque->hasho_flag = LH_META_PAGE;
- pageopaque->hasho_filler = HASHO_FILL;
+ pageopaque->hasho_page_id = HASHO_PAGE_ID;
- metap = (HashMetaPage) pg;
+ metap = HashPageGetMeta(pg);
metap->hashm_magic = HASH_MAGIC;
metap->hashm_version = HASH_VERSION;
metap->hashm_ntuples = 0;
metap->hashm_nmaps = 0;
metap->hashm_ffactor = ffactor;
- metap->hashm_bsize = BufferGetPageSize(metabuf);
+ metap->hashm_bsize = HashGetMaxBitmapSize(pg);
/* find largest bitmap array size that will fit in page size */
for (i = _hash_log2(metap->hashm_bsize); i > 0; --i)
{
- if ((1 << i) <= (metap->hashm_bsize -
- (MAXALIGN(sizeof(PageHeaderData)) +
- MAXALIGN(sizeof(HashPageOpaqueData)))))
+ if ((1 << i) <= metap->hashm_bsize)
break;
}
Assert(i > 0);
metap->hashm_bmshift = i + BYTE_TO_BIT;
Assert((1 << BMPG_SHIFT(metap)) == (BMPG_MASK(metap) + 1));
+ /*
+ * Label the index with its primary hash support function's OID. This is
+ * pretty useless for normal operation (in fact, hashm_procid is not used
+ * anywhere), but it might be handy for forensic purposes so we keep it.
+ */
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 N buckets, 0 .. N-1, occupying physical
+ * blocks 1 to N. The first freespace bitmap page is in block N+1. Since
+ * N is a power of 2, we can set the masks this way:
*/
- metap->hashm_maxbucket = metap->hashm_lowmask = 1; /* nbuckets - 1 */
- metap->hashm_highmask = 3; /* (nbuckets << 1) - 1 */
+ metap->hashm_maxbucket = metap->hashm_lowmask = num_buckets - 1;
+ metap->hashm_highmask = (num_buckets << 1) - 1;
MemSet(metap->hashm_spares, 0, sizeof(metap->hashm_spares));
MemSet(metap->hashm_mapp, 0, sizeof(metap->hashm_mapp));
- metap->hashm_spares[1] = 1; /* the first bitmap page is only spare */
- metap->hashm_ovflpoint = 1;
+ /* Set up mapping for one spare page after the initial splitpoints */
+ metap->hashm_spares[log2_num_buckets] = 1;
+ metap->hashm_ovflpoint = log2_num_buckets;
metap->hashm_firstfree = 0;
/*
- * Initialize the first two buckets
+ * Release buffer lock on the metapage while we initialize buckets.
+ * Otherwise, we'll be in interrupt holdoff and the CHECK_FOR_INTERRUPTS
+ * won't accomplish anything. It's a bad idea to hold buffer locks for
+ * long intervals in any case, since that can block the bgwriter.
+ */
+ _hash_chgbufaccess(rel, metabuf, HASH_WRITE, HASH_NOLOCK);
+
+ /*
+ * Initialize the first N buckets
*/
- for (i = 0; i <= 1; i++)
+ for (i = 0; i < num_buckets; i++)
{
- buf = _hash_getbuf(rel, BUCKET_TO_BLKNO(metap, i), HASH_WRITE);
+ /* Allow interrupts, in case N is huge */
+ CHECK_FOR_INTERRUPTS();
+
+ buf = _hash_getnewbuf(rel, BUCKET_TO_BLKNO(metap, i), forkNum);
pg = BufferGetPage(buf);
- _hash_pageinit(pg, BufferGetPageSize(buf));
pageopaque = (HashPageOpaque) PageGetSpecialPointer(pg);
pageopaque->hasho_prevblkno = InvalidBlockNumber;
pageopaque->hasho_nextblkno = InvalidBlockNumber;
pageopaque->hasho_bucket = i;
pageopaque->hasho_flag = LH_BUCKET_PAGE;
- pageopaque->hasho_filler = HASHO_FILL;
+ pageopaque->hasho_page_id = HASHO_PAGE_ID;
_hash_wrtbuf(rel, buf);
}
+ /* Now reacquire buffer lock on metapage */
+ _hash_chgbufaccess(rel, metabuf, HASH_NOLOCK, HASH_WRITE);
+
/*
- * Initialize first bitmap page. Can't do this until we create the first
- * two buckets, else smgr will complain.
+ * Initialize first bitmap page
*/
- _hash_initbitmap(rel, metap, 3);
+ _hash_initbitmap(rel, metap, num_buckets + 1, forkNum);
/* all done */
_hash_wrtbuf(rel, metabuf);
+
+ return num_buckets;
}
/*
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);
- metap = (HashMetaPage) BufferGetPage(metabuf);
+ metap = HashPageGetMeta(BufferGetPage(metabuf));
/*
* Check to see if split is still needed; someone else might have already
(double) metap->hashm_ffactor * (metap->hashm_maxbucket + 1))
goto fail;
+ /*
+ * Can't split anymore if maxbucket has reached its maximum possible
+ * value.
+ *
+ * Ideally we'd allow bucket numbers up to UINT_MAX-1 (no higher because
+ * the calculation maxbucket+1 mustn't overflow). Currently we restrict
+ * to half that because of overflow looping in _hash_log2() and
+ * insufficient space in hashm_spares[]. It's moot anyway because an
+ * index with 2^32 buckets would certainly overflow BlockNumber and hence
+ * _hash_alloc_buckets() would fail, but if we supported buckets smaller
+ * than a disk block then this would be an independent constraint.
+ *
+ * If you change this, see also the maximum initial number of buckets in
+ * _hash_metapinit().
+ */
+ if (metap->hashm_maxbucket >= (uint32) 0x7FFFFFFE)
+ goto fail;
+
/*
* 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 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...
*/
new_bucket = metap->hashm_maxbucket + 1;
+
old_bucket = (new_bucket & metap->hashm_lowmask);
start_oblkno = BUCKET_TO_BLKNO(metap, old_bucket);
goto fail;
/*
- * Okay to proceed with split. Update the metapage bucket mapping info.
+ * Likewise lock the new bucket (should never fail).
+ *
+ * Note: it is safe to compute the new bucket's blkno here, even though we
+ * may still need to update the BUCKET_TO_BLKNO mapping. This is because
+ * the current value of hashm_spares[hashm_ovflpoint] correctly shows
+ * where we are going to put a new splitpoint's worth of buckets.
+ */
+ start_nblkno = BUCKET_TO_BLKNO(metap, new_bucket);
+
+ if (_hash_has_active_scan(rel, new_bucket))
+ elog(ERROR, "scan in progress on supposedly new bucket");
+
+ if (!_hash_try_getlock(rel, start_nblkno, HASH_EXCLUSIVE))
+ elog(ERROR, "could not get lock on supposedly new bucket");
+
+ /*
+ * If the split point is increasing (hashm_maxbucket's log base 2
+ * increases), we need to allocate a new batch of bucket pages.
+ */
+ spare_ndx = _hash_log2(new_bucket + 1);
+ if (spare_ndx > metap->hashm_ovflpoint)
+ {
+ Assert(spare_ndx == metap->hashm_ovflpoint + 1);
+
+ /*
+ * The number of buckets in the new splitpoint is equal to the total
+ * number already in existence, i.e. new_bucket. Currently this maps
+ * one-to-one to blocks required, but someday we may need a more
+ * complicated calculation here.
+ */
+ if (!_hash_alloc_buckets(rel, start_nblkno, new_bucket))
+ {
+ /* can't split due to BlockNumber overflow */
+ _hash_droplock(rel, start_oblkno, HASH_EXCLUSIVE);
+ _hash_droplock(rel, start_nblkno, HASH_EXCLUSIVE);
+ goto fail;
+ }
+ }
+
+ /*
+ * 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
* 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.
- *
- * 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)
{
- Assert(spare_ndx == metap->hashm_ovflpoint + 1);
metap->hashm_spares[spare_ndx] = metap->hashm_spares[metap->hashm_ovflpoint];
metap->hashm_ovflpoint = spare_ndx;
}
- /* now we can compute the new bucket's primary block number */
- start_nblkno = BUCKET_TO_BLKNO(metap, new_bucket);
-
- Assert(!_hash_has_active_scan(rel, new_bucket));
-
- if (!_hash_try_getlock(rel, start_nblkno, HASH_EXCLUSIVE))
- elog(PANIC, "could not get lock on supposedly new bucket");
-
/* Done mucking with metapage */
END_CRIT_SECTION();
* 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);
+}
+
+
+/*
+ * _hash_alloc_buckets -- allocate a new splitpoint's worth of bucket pages
+ *
+ * This does not need to initialize the new bucket pages; we'll do that as
+ * each one is used by _hash_expandtable(). But we have to extend the logical
+ * EOF to the end of the splitpoint; this keeps smgr's idea of the EOF in
+ * sync with ours, so that we don't get complaints from smgr.
+ *
+ * We do this by writing a page of zeroes at the end of the splitpoint range.
+ * We expect that the filesystem will ensure that the intervening pages read
+ * as zeroes too. On many filesystems this "hole" will not be allocated
+ * immediately, which means that the index file may end up more fragmented
+ * than if we forced it all to be allocated now; but since we don't scan
+ * hash indexes sequentially anyway, that probably doesn't matter.
+ *
+ * XXX It's annoying that this code is executed with the metapage lock held.
+ * We need to interlock against _hash_getovflpage() adding a new overflow page
+ * concurrently, but it'd likely be better to use LockRelationForExtension
+ * for the purpose. OTOH, adding a splitpoint is a very infrequent operation,
+ * so it may not be worth worrying about.
+ *
+ * Returns TRUE if successful, or FALSE if allocation failed due to
+ * BlockNumber overflow.
+ */
+static bool
+_hash_alloc_buckets(Relation rel, BlockNumber firstblock, uint32 nblocks)
+{
+ BlockNumber lastblock;
+ char zerobuf[BLCKSZ];
+
+ lastblock = firstblock + nblocks - 1;
- /* Release split lock */
- _hash_droplock(rel, 0, HASH_EXCLUSIVE);
+ /*
+ * Check for overflow in block number calculation; if so, we cannot extend
+ * the index anymore.
+ */
+ if (lastblock < firstblock || lastblock == InvalidBlockNumber)
+ return false;
+
+ MemSet(zerobuf, 0, sizeof(zerobuf));
+
+ RelationOpenSmgr(rel);
+ smgrextend(rel->rd_smgr, MAIN_FORKNUM, lastblock, zerobuf, false);
+
+ return true;
}
uint32 highmask,
uint32 lowmask)
{
- Bucket bucket;
- Buffer obuf;
- Buffer nbuf;
BlockNumber oblkno;
BlockNumber nblkno;
- bool null;
- Datum datum;
- HashItem hitem;
- HashPageOpaque oopaque;
- HashPageOpaque nopaque;
- IndexTuple itup;
- Size itemsz;
- OffsetNumber ooffnum;
- OffsetNumber noffnum;
- OffsetNumber omaxoffnum;
+ Buffer obuf;
+ Buffer nbuf;
Page opage;
Page npage;
- TupleDesc itupdesc = RelationGetDescr(rel);
+ HashPageOpaque oopaque;
+ HashPageOpaque nopaque;
/*
* It should be okay to simultaneously write-lock pages from each bucket,
* either bucket.
*/
oblkno = start_oblkno;
- obuf = _hash_getbuf(rel, oblkno, HASH_WRITE);
- _hash_checkpage(rel, obuf, LH_BUCKET_PAGE);
+ obuf = _hash_getbuf(rel, oblkno, HASH_WRITE, LH_BUCKET_PAGE);
opage = BufferGetPage(obuf);
oopaque = (HashPageOpaque) PageGetSpecialPointer(opage);
nblkno = start_nblkno;
- nbuf = _hash_getbuf(rel, nblkno, HASH_WRITE);
+ nbuf = _hash_getnewbuf(rel, nblkno, MAIN_FORKNUM);
npage = BufferGetPage(nbuf);
/* initialize the new bucket's primary page */
- _hash_pageinit(npage, BufferGetPageSize(nbuf));
nopaque = (HashPageOpaque) PageGetSpecialPointer(npage);
nopaque->hasho_prevblkno = InvalidBlockNumber;
nopaque->hasho_nextblkno = InvalidBlockNumber;
nopaque->hasho_bucket = nbucket;
nopaque->hasho_flag = LH_BUCKET_PAGE;
- nopaque->hasho_filler = HASHO_FILL;
+ nopaque->hasho_page_id = HASHO_PAGE_ID;
/*
* 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.
+ * adding overflow pages to the new bucket as needed. Outer loop iterates
+ * once per page in old bucket.
*/
- ooffnum = FirstOffsetNumber;
- omaxoffnum = PageGetMaxOffsetNumber(opage);
for (;;)
{
- /*
- * at each iteration through this loop, each of these variables should
- * be up-to-date: obuf opage oopaque ooffnum omaxoffnum
- */
-
- /* check if we're at the end of the page */
- if (ooffnum > omaxoffnum)
+ OffsetNumber ooffnum;
+ OffsetNumber omaxoffnum;
+ OffsetNumber deletable[MaxOffsetNumber];
+ int ndeletable = 0;
+
+ /* Scan each tuple in old page */
+ omaxoffnum = PageGetMaxOffsetNumber(opage);
+ for (ooffnum = FirstOffsetNumber;
+ ooffnum <= omaxoffnum;
+ ooffnum = OffsetNumberNext(ooffnum))
{
- /* at end of page, but check for an(other) overflow page */
- oblkno = oopaque->hasho_nextblkno;
- if (!BlockNumberIsValid(oblkno))
- break;
+ IndexTuple itup;
+ Size itemsz;
+ Bucket bucket;
/*
- * we ran out of tuples on this particular page, but we have more
- * overflow pages; advance to next page.
+ * Fetch the item's hash key (conveniently stored in the item) and
+ * determine which bucket it now belongs in.
*/
- _hash_wrtbuf(rel, obuf);
+ itup = (IndexTuple) PageGetItem(opage,
+ PageGetItemId(opage, ooffnum));
+ bucket = _hash_hashkey2bucket(_hash_get_indextuple_hashkey(itup),
+ maxbucket, highmask, lowmask);
- obuf = _hash_getbuf(rel, oblkno, HASH_WRITE);
- _hash_checkpage(rel, obuf, LH_OVERFLOW_PAGE);
- opage = BufferGetPage(obuf);
- oopaque = (HashPageOpaque) PageGetSpecialPointer(opage);
- ooffnum = FirstOffsetNumber;
- omaxoffnum = PageGetMaxOffsetNumber(opage);
- continue;
+ if (bucket == nbucket)
+ {
+ /*
+ * insert the tuple into the new bucket. if it doesn't fit on
+ * the current page in the new bucket, we must allocate a new
+ * overflow page and place the tuple on that page instead.
+ */
+ itemsz = IndexTupleDSize(*itup);
+ itemsz = MAXALIGN(itemsz);
+
+ if (PageGetFreeSpace(npage) < itemsz)
+ {
+ /* write out nbuf and drop lock, but keep pin */
+ _hash_chgbufaccess(rel, nbuf, HASH_WRITE, HASH_NOLOCK);
+ /* chain to a new overflow page */
+ nbuf = _hash_addovflpage(rel, metabuf, nbuf);
+ npage = BufferGetPage(nbuf);
+ /* we don't need nblkno or nopaque within the loop */
+ }
+
+ /*
+ * Insert tuple on new page, using _hash_pgaddtup to ensure
+ * correct ordering by hashkey. This is a tad inefficient
+ * since we may have to shuffle itempointers repeatedly.
+ * Possible future improvement: accumulate all the items for
+ * the new page and qsort them before insertion.
+ */
+ (void) _hash_pgaddtup(rel, nbuf, itemsz, itup);
+
+ /*
+ * Mark tuple for deletion from old page.
+ */
+ deletable[ndeletable++] = ooffnum;
+ }
+ else
+ {
+ /*
+ * the tuple stays on this page, so nothing to do.
+ */
+ Assert(bucket == obucket);
+ }
}
+ oblkno = oopaque->hasho_nextblkno;
+
/*
- * 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 too.
+ * Done scanning this old page. If we moved any tuples, delete them
+ * from the old page.
*/
- hitem = (HashItem) PageGetItem(opage, PageGetItemId(opage, ooffnum));
- itup = &(hitem->hash_itup);
- datum = index_getattr(itup, 1, itupdesc, &null);
- Assert(!null);
-
- bucket = _hash_hashkey2bucket(_hash_datum2hashkey(rel, datum),
- maxbucket, highmask, lowmask);
-
- if (bucket == nbucket)
+ if (ndeletable > 0)
{
- /*
- * insert the tuple into the new bucket. if it doesn't fit on the
- * current page in the new bucket, we must allocate a new overflow
- * page and place the tuple on that page instead.
- */
- itemsz = IndexTupleDSize(hitem->hash_itup)
- + (sizeof(HashItemData) - sizeof(IndexTupleData));
-
- itemsz = MAXALIGN(itemsz);
-
- if (PageGetFreeSpace(npage) < itemsz)
- {
- /* write out nbuf and drop lock, but keep pin */
- _hash_chgbufaccess(rel, nbuf, HASH_WRITE, HASH_NOLOCK);
- /* chain to a new overflow page */
- nbuf = _hash_addovflpage(rel, metabuf, nbuf);
- _hash_checkpage(rel, nbuf, LH_OVERFLOW_PAGE);
- npage = BufferGetPage(nbuf);
- /* we don't need nopaque within the loop */
- }
-
- noffnum = OffsetNumberNext(PageGetMaxOffsetNumber(npage));
- if (PageAddItem(npage, (Item) hitem, itemsz, noffnum, LP_USED)
- == InvalidOffsetNumber)
- elog(ERROR, "failed to add index item to \"%s\"",
- RelationGetRelationName(rel));
-
- /*
- * now delete the tuple from the old bucket. after this section
- * of code, 'ooffnum' will actually point to the ItemId to which
- * we would point if we had advanced it before the deletion
- * (PageIndexTupleDelete repacks the ItemId array). this also
- * means that 'omaxoffnum' is exactly one less than it used to be,
- * so we really can just decrement it instead of calling
- * PageGetMaxOffsetNumber.
- */
- PageIndexTupleDelete(opage, ooffnum);
- omaxoffnum = OffsetNumberPrev(omaxoffnum);
+ PageIndexMultiDelete(opage, deletable, ndeletable);
+ _hash_wrtbuf(rel, obuf);
}
else
- {
- /*
- * the tuple stays on this page. we didn't move anything, so we
- * didn't delete anything and therefore we don't have to change
- * 'omaxoffnum'.
- */
- Assert(bucket == obucket);
- ooffnum = OffsetNumberNext(ooffnum);
- }
+ _hash_relbuf(rel, obuf);
+
+ /* Exit loop if no more overflow pages in old bucket */
+ if (!BlockNumberIsValid(oblkno))
+ break;
+
+ /* Else, advance to next old page */
+ obuf = _hash_getbuf(rel, oblkno, HASH_WRITE, LH_OVERFLOW_PAGE);
+ opage = BufferGetPage(obuf);
+ oopaque = (HashPageOpaque) PageGetSpecialPointer(opage);
}
/*
* 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.
*/
- _hash_wrtbuf(rel, obuf);
_hash_wrtbuf(rel, nbuf);
- _hash_squeezebucket(rel, obucket, start_oblkno);
+ _hash_squeezebucket(rel, obucket, start_oblkno, NULL);
}
projects / postgresql / blobdiff