* hashpage.c
* Hash table page management code for the Postgres hash access method
*
- * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/access/hash/hashpage.c,v 1.76 2008/08/11 11:05:10 heikki 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 "access/hash_xlog.h"
#include "miscadmin.h"
-#include "storage/bufmgr.h"
#include "storage/lmgr.h"
#include "storage/smgr.h"
-#include "utils/lsyscache.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,
- BlockNumber start_nblkno,
+ Buffer obuf,
+ Buffer nbuf,
+ HTAB *htab,
uint32 maxbucket,
uint32 highmask, uint32 lowmask);
+static void log_split_page(Relation rel, Buffer buf);
/*
* 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.)
- *
- * 'access' must be HASH_SHARE or HASH_EXCLUSIVE.
- */
-void
-_hash_getlock(Relation rel, BlockNumber whichlock, int access)
-{
- if (USELOCKING(rel))
- LockPage(rel, whichlock, access);
-}
-
-/*
- * _hash_try_getlock() -- Acquire an lmgr lock, but only if it's free.
- *
- * Same as above except we return FALSE without blocking if lock isn't free.
- */
-bool
-_hash_try_getlock(Relation rel, BlockNumber whichlock, int access)
-{
- if (USELOCKING(rel))
- return ConditionalLockPage(rel, whichlock, access);
- else
- return true;
-}
-
-/*
- * _hash_droplock() -- Release an lmgr lock.
- */
-void
-_hash_droplock(Relation rel, BlockNumber whichlock, int access)
-{
- if (USELOCKING(rel))
- UnlockPage(rel, whichlock, access);
-}
-
/*
* _hash_getbuf() -- Get a buffer by block number for read or write.
*
return buf;
}
+/*
+ * _hash_getbuf_with_condlock_cleanup() -- Try to get a buffer for cleanup.
+ *
+ * We read the page and try to acquire a cleanup lock. If we get it,
+ * we return the buffer; otherwise, we return InvalidBuffer.
+ */
+Buffer
+_hash_getbuf_with_condlock_cleanup(Relation rel, BlockNumber blkno, int flags)
+{
+ Buffer buf;
+
+ if (blkno == P_NEW)
+ elog(ERROR, "hash AM does not use P_NEW");
+
+ buf = ReadBuffer(rel, blkno);
+
+ if (!ConditionalLockBufferForCleanup(buf))
+ {
+ ReleaseBuffer(buf);
+ return InvalidBuffer;
+ }
+
+ /* 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
+ * _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
if (blkno == P_NEW)
elog(ERROR, "hash AM does not use P_NEW");
- buf = ReadOrZeroBuffer(rel, MAIN_FORKNUM, blkno);
-
- LockBuffer(buf, HASH_WRITE);
+ buf = ReadBufferExtended(rel, MAIN_FORKNUM, blkno, RBM_ZERO_AND_LOCK,
+ NULL);
/* ref count and lock type are correct */
return buf;
}
+/*
+ * _hash_initbuf() -- Get and initialize a buffer by bucket number.
+ */
+void
+_hash_initbuf(Buffer buf, uint32 max_bucket, uint32 num_bucket, uint32 flag,
+ bool initpage)
+{
+ HashPageOpaque pageopaque;
+ Page page;
+
+ page = BufferGetPage(buf);
+
+ /* initialize the page */
+ if (initpage)
+ _hash_pageinit(page, BufferGetPageSize(buf));
+
+ pageopaque = (HashPageOpaque) PageGetSpecialPointer(page);
+
+ /*
+ * Set hasho_prevblkno with current hashm_maxbucket. This value will be
+ * used to validate cached HashMetaPageData. See
+ * _hash_getbucketbuf_from_hashkey().
+ */
+ pageopaque->hasho_prevblkno = max_bucket;
+ pageopaque->hasho_nextblkno = InvalidBlockNumber;
+ pageopaque->hasho_bucket = num_bucket;
+ pageopaque->hasho_flag = flag;
+ pageopaque->hasho_page_id = HASHO_PAGE_ID;
+}
+
/*
* _hash_getnewbuf() -- Get a new page at the end of the index.
*
* 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.
+ * extend the index at a time. In practice, this function is called
+ * only while holding write lock on the metapage, because adding a page
+ * is always associated with an update of metapage data.
*/
Buffer
-_hash_getnewbuf(Relation rel, BlockNumber blkno)
+_hash_getnewbuf(Relation rel, BlockNumber blkno, ForkNumber forkNum)
{
- BlockNumber nblocks = RelationGetNumberOfBlocks(rel);
+ BlockNumber nblocks = RelationGetNumberOfBlocksInFork(rel, forkNum);
Buffer buf;
if (blkno == P_NEW)
/* smgr insists we use P_NEW to extend the relation */
if (blkno == nblocks)
{
- buf = ReadBuffer(rel, P_NEW);
+ 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);
+ LockBuffer(buf, HASH_WRITE);
}
else
- buf = ReadOrZeroBuffer(rel, MAIN_FORKNUM, blkno);
-
- LockBuffer(buf, HASH_WRITE);
+ {
+ buf = ReadBufferExtended(rel, forkNum, blkno, RBM_ZERO_AND_LOCK,
+ NULL);
+ }
/* ref count and lock type are correct */
if (blkno == P_NEW)
elog(ERROR, "hash AM does not use P_NEW");
- buf = ReadBufferWithStrategy(rel, blkno, bstrategy);
+ buf = ReadBufferExtended(rel, MAIN_FORKNUM, blkno, RBM_NORMAL, bstrategy);
if (access != HASH_NOLOCK)
LockBuffer(buf, access);
}
/*
- * _hash_wrtbuf() -- write a hash page to disk.
- *
- * This routine releases the lock held on the buffer and our refcount
- * for it. It is an error to call _hash_wrtbuf() without a write lock
- * and a pin on the buffer.
- *
- * 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)
-{
- MarkBufferDirty(buf);
- UnlockReleaseBuffer(buf);
-}
-
-/*
- * _hash_chgbufaccess() -- Change the lock type on a buffer, without
- * dropping our pin on it.
+ * _hash_dropscanbuf() -- release buffers used in scan.
*
- * from_access and to_access may be HASH_READ, HASH_WRITE, or HASH_NOLOCK,
- * the last indicating that no buffer-level lock is held or wanted.
- *
- * When from_access == HASH_WRITE, we assume the buffer is dirty and tell
- * bufmgr it must be written out. If the caller wants to release a write
- * lock on a page that's not been modified, it's okay to pass from_access
- * as HASH_READ (a bit ugly, but handy in some places).
+ * This routine unpins the buffers used during scan on which we
+ * hold no lock.
*/
void
-_hash_chgbufaccess(Relation rel,
- Buffer buf,
- int from_access,
- int to_access)
+_hash_dropscanbuf(Relation rel, HashScanOpaque so)
{
- if (from_access == HASH_WRITE)
- MarkBufferDirty(buf);
- if (from_access != HASH_NOLOCK)
- LockBuffer(buf, BUFFER_LOCK_UNLOCK);
- if (to_access != HASH_NOLOCK)
- LockBuffer(buf, to_access);
+ /* release pin we hold on primary bucket page */
+ if (BufferIsValid(so->hashso_bucket_buf) &&
+ so->hashso_bucket_buf != so->currPos.buf)
+ _hash_dropbuf(rel, so->hashso_bucket_buf);
+ so->hashso_bucket_buf = InvalidBuffer;
+
+ /* release pin we hold on primary bucket page of bucket being split */
+ if (BufferIsValid(so->hashso_split_bucket_buf) &&
+ so->hashso_split_bucket_buf != so->currPos.buf)
+ _hash_dropbuf(rel, so->hashso_split_bucket_buf);
+ so->hashso_split_bucket_buf = InvalidBuffer;
+
+ /* release any pin we still hold */
+ if (BufferIsValid(so->currPos.buf))
+ _hash_dropbuf(rel, so->currPos.buf);
+ so->currPos.buf = InvalidBuffer;
+
+ /* reset split scan */
+ so->hashso_buc_populated = false;
+ so->hashso_buc_split = false;
}
/*
- * _hash_metapinit() -- Initialize the metadata page of a hash index,
+ * _hash_init() -- Initialize the metadata page of a hash index,
* the initial buckets, and the initial bitmap page.
*
* The initial number of buckets is dependent on num_tuples, an estimate
* multiple buffer locks is ignored.
*/
uint32
-_hash_metapinit(Relation rel, double num_tuples)
+_hash_init(Relation rel, double num_tuples, ForkNumber forkNum)
{
- HashMetaPage metap;
- HashPageOpaque pageopaque;
Buffer metabuf;
Buffer buf;
+ Buffer bitmapbuf;
Page pg;
+ HashMetaPage metap;
+ RegProcedure procid;
int32 data_width;
int32 item_width;
int32 ffactor;
- double dnumbuckets;
uint32 num_buckets;
- uint32 log2_num_buckets;
uint32 i;
+ bool use_wal;
/* safety check */
- if (RelationGetNumberOfBlocks(rel) != 0)
+ if (RelationGetNumberOfBlocksInFork(rel, forkNum) != 0)
elog(ERROR, "cannot initialize non-empty hash index \"%s\"",
RelationGetRelationName(rel));
+ /*
+ * WAL log creation of pages if the relation is persistent, or this is the
+ * init fork. Init forks for unlogged relations always need to be WAL
+ * logged.
+ */
+ use_wal = RelationNeedsWAL(rel) || forkNum == INIT_FORKNUM;
+
/*
* 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 if the index datatype is fixed-width, but for var-width there's
- * some guessing involved.
+ * 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);
+ data_width = sizeof(uint32);
item_width = MAXALIGN(sizeof(IndexTupleData)) + MAXALIGN(data_width) +
sizeof(ItemIdData); /* include the line pointer */
ffactor = RelationGetTargetPageUsage(rel, HASH_DEFAULT_FILLFACTOR) / item_width;
if (ffactor < 10)
ffactor = 10;
+ procid = index_getprocid(rel, 1, HASHSTANDARD_PROC);
+
+ /*
+ * 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.
+ *
+ * Critical section not required, because on error the creation of the
+ * whole relation will be rolled back.
+ */
+ metabuf = _hash_getnewbuf(rel, HASH_METAPAGE, forkNum);
+ _hash_init_metabuffer(metabuf, num_tuples, procid, ffactor, false);
+ MarkBufferDirty(metabuf);
+
+ pg = BufferGetPage(metabuf);
+ metap = HashPageGetMeta(pg);
+
+ /* XLOG stuff */
+ if (use_wal)
+ {
+ xl_hash_init_meta_page xlrec;
+ XLogRecPtr recptr;
+
+ xlrec.num_tuples = num_tuples;
+ xlrec.procid = metap->hashm_procid;
+ xlrec.ffactor = metap->hashm_ffactor;
+
+ XLogBeginInsert();
+ XLogRegisterData((char *) &xlrec, SizeOfHashInitMetaPage);
+ XLogRegisterBuffer(0, metabuf, REGBUF_WILL_INIT | REGBUF_STANDARD);
+
+ recptr = XLogInsert(RM_HASH_ID, XLOG_HASH_INIT_META_PAGE);
+
+ PageSetLSN(BufferGetPage(metabuf), recptr);
+ }
+
+ num_buckets = metap->hashm_maxbucket + 1;
+
+ /*
+ * 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.
+ */
+ LockBuffer(metabuf, BUFFER_LOCK_UNLOCK);
+
+ /*
+ * Initialize and WAL Log the first N buckets
+ */
+ for (i = 0; i < num_buckets; i++)
+ {
+ BlockNumber blkno;
+
+ /* Allow interrupts, in case N is huge */
+ CHECK_FOR_INTERRUPTS();
+
+ blkno = BUCKET_TO_BLKNO(metap, i);
+ buf = _hash_getnewbuf(rel, blkno, forkNum);
+ _hash_initbuf(buf, metap->hashm_maxbucket, i, LH_BUCKET_PAGE, false);
+ MarkBufferDirty(buf);
+
+ if (use_wal)
+ log_newpage(&rel->rd_node,
+ forkNum,
+ blkno,
+ BufferGetPage(buf),
+ true);
+ _hash_relbuf(rel, buf);
+ }
+
+ /* Now reacquire buffer lock on metapage */
+ LockBuffer(metabuf, BUFFER_LOCK_EXCLUSIVE);
+
+ /*
+ * Initialize bitmap page
+ */
+ bitmapbuf = _hash_getnewbuf(rel, num_buckets + 1, forkNum);
+ _hash_initbitmapbuffer(bitmapbuf, metap->hashm_bmsize, false);
+ MarkBufferDirty(bitmapbuf);
+
+ /* add the new bitmap page to the metapage's list of bitmaps */
+ /* metapage already has a write lock */
+ if (metap->hashm_nmaps >= HASH_MAX_BITMAPS)
+ ereport(ERROR,
+ (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+ errmsg("out of overflow pages in hash index \"%s\"",
+ RelationGetRelationName(rel))));
+
+ metap->hashm_mapp[metap->hashm_nmaps] = num_buckets + 1;
+
+ metap->hashm_nmaps++;
+ MarkBufferDirty(metabuf);
+
+ /* XLOG stuff */
+ if (use_wal)
+ {
+ xl_hash_init_bitmap_page xlrec;
+ XLogRecPtr recptr;
+
+ xlrec.bmsize = metap->hashm_bmsize;
+
+ XLogBeginInsert();
+ XLogRegisterData((char *) &xlrec, SizeOfHashInitBitmapPage);
+ XLogRegisterBuffer(0, bitmapbuf, REGBUF_WILL_INIT);
+
+ /*
+ * This is safe only because nobody else can be modifying the index at
+ * this stage; it's only visible to the transaction that is creating
+ * it.
+ */
+ XLogRegisterBuffer(1, metabuf, REGBUF_STANDARD);
+
+ recptr = XLogInsert(RM_HASH_ID, XLOG_HASH_INIT_BITMAP_PAGE);
+
+ PageSetLSN(BufferGetPage(bitmapbuf), recptr);
+ PageSetLSN(BufferGetPage(metabuf), recptr);
+ }
+
+ /* all done */
+ _hash_relbuf(rel, bitmapbuf);
+ _hash_relbuf(rel, metabuf);
+
+ return num_buckets;
+}
+
+/*
+ * _hash_init_metabuffer() -- Initialize the metadata page of a hash index.
+ */
+void
+_hash_init_metabuffer(Buffer buf, double num_tuples, RegProcedure procid,
+ uint16 ffactor, bool initpage)
+{
+ HashMetaPage metap;
+ HashPageOpaque pageopaque;
+ Page page;
+ double dnumbuckets;
+ uint32 num_buckets;
+ uint32 spare_index;
+ uint32 i;
+
/*
* 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
+ * total number of buckets which has to be allocated before using its
+ * _hashm_spare element. However always force at least 2 bucket pages. The
+ * upper limit is determined by considerations explained in
* _hash_expandtable().
*/
dnumbuckets = num_tuples / ffactor;
else if (dnumbuckets >= (double) 0x40000000)
num_buckets = 0x40000000;
else
- num_buckets = ((uint32) 1) << _hash_log2((uint32) dnumbuckets);
+ num_buckets = _hash_get_totalbuckets(_hash_spareindex(dnumbuckets));
- log2_num_buckets = _hash_log2(num_buckets);
- Assert(num_buckets == (((uint32) 1) << log2_num_buckets));
- Assert(log2_num_buckets < HASH_MAX_SPLITPOINTS);
+ spare_index = _hash_spareindex(num_buckets);
+ Assert(spare_index < 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);
- pg = BufferGetPage(metabuf);
+ page = BufferGetPage(buf);
+ if (initpage)
+ _hash_pageinit(page, BufferGetPageSize(buf));
- pageopaque = (HashPageOpaque) PageGetSpecialPointer(pg);
+ pageopaque = (HashPageOpaque) PageGetSpecialPointer(page);
pageopaque->hasho_prevblkno = InvalidBlockNumber;
pageopaque->hasho_nextblkno = InvalidBlockNumber;
pageopaque->hasho_bucket = -1;
pageopaque->hasho_flag = LH_META_PAGE;
pageopaque->hasho_page_id = HASHO_PAGE_ID;
- metap = (HashMetaPage) pg;
+ metap = HashPageGetMeta(page);
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(page);
/* 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);
* 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);
+ metap->hashm_procid = procid;
/*
* 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 = num_buckets - 1;
- metap->hashm_highmask = (num_buckets << 1) - 1;
+ metap->hashm_maxbucket = num_buckets - 1;
+
+ /*
+ * Set highmask as next immediate ((2 ^ x) - 1), which should be
+ * sufficient to cover num_buckets.
+ */
+ metap->hashm_highmask = (1 << (_hash_log2(num_buckets + 1))) - 1;
+ metap->hashm_lowmask = (metap->hashm_highmask >> 1);
MemSet(metap->hashm_spares, 0, sizeof(metap->hashm_spares));
MemSet(metap->hashm_mapp, 0, sizeof(metap->hashm_mapp));
/* 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_spares[spare_index] = 1;
+ metap->hashm_ovflpoint = spare_index;
metap->hashm_firstfree = 0;
/*
- * 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
+ * Set pd_lower just past the end of the metadata. This is essential,
+ * because without doing so, metadata will be lost if xlog.c compresses
+ * the page.
*/
- for (i = 0; i < num_buckets; i++)
- {
- /* Allow interrupts, in case N is huge */
- CHECK_FOR_INTERRUPTS();
-
- buf = _hash_getnewbuf(rel, BUCKET_TO_BLKNO(metap, i));
- pg = BufferGetPage(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_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
- */
- _hash_initbitmap(rel, metap, num_buckets + 1);
-
- /* all done */
- _hash_wrtbuf(rel, metabuf);
-
- return num_buckets;
+ ((PageHeader) page)->pd_lower =
+ ((char *) metap + sizeof(HashMetaPageData)) - (char *) page;
}
/*
void
_hash_pageinit(Page page, Size size)
{
- Assert(PageIsNew(page));
PageInit(page, size, sizeof(HashPageOpaqueData));
}
/*
* Attempt to expand the hash table by creating one new bucket.
*
- * This will silently do nothing if it cannot get the needed locks.
+ * This will silently do nothing if we don't get cleanup lock on old or
+ * new bucket.
*
- * The caller should hold no locks on the hash index.
+ * Complete the pending splits and remove the tuples from old bucket,
+ * if there are any left over from the previous split.
*
* The caller must hold a pin, but no lock, on the metapage buffer.
* The buffer is returned in the same state.
uint32 spare_ndx;
BlockNumber start_oblkno;
BlockNumber start_nblkno;
+ Buffer buf_nblkno;
+ Buffer buf_oblkno;
+ Page opage;
+ Page npage;
+ HashPageOpaque oopaque;
+ HashPageOpaque nopaque;
uint32 maxbucket;
uint32 highmask;
uint32 lowmask;
+ bool metap_update_masks = false;
+ bool metap_update_splitpoint = false;
+
+restart_expand:
/*
- * 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);
+ LockBuffer(metabuf, BUFFER_LOCK_EXCLUSIVE);
_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
* _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 you change this, see also the maximum initial number of buckets in
+ * _hash_init().
*/
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.
+ * Determine which bucket is to be split, and attempt to take cleanup lock
+ * on the old 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.
+ * The cleanup lock protects us not only against other backends, but
+ * against our own backend as well.
+ *
+ * The cleanup lock is mainly to protect the split from concurrent
+ * inserts. See src/backend/access/hash/README, Lock Definitions for
+ * further details. Due to this locking restriction, if there is any
+ * pending scan, the split will give up which is not good, but harmless.
*/
new_bucket = metap->hashm_maxbucket + 1;
start_oblkno = BUCKET_TO_BLKNO(metap, old_bucket);
- if (_hash_has_active_scan(rel, old_bucket))
+ buf_oblkno = _hash_getbuf_with_condlock_cleanup(rel, start_oblkno, LH_BUCKET_PAGE);
+ if (!buf_oblkno)
goto fail;
- if (!_hash_try_getlock(rel, start_oblkno, HASH_EXCLUSIVE))
- goto fail;
+ opage = BufferGetPage(buf_oblkno);
+ oopaque = (HashPageOpaque) PageGetSpecialPointer(opage);
/*
- * Likewise lock the new bucket (should never fail).
+ * We want to finish the split from a bucket as there is no apparent
+ * benefit by not doing so and it will make the code complicated to finish
+ * the split that involves multiple buckets considering the case where new
+ * split also fails. We don't need to consider the new bucket for
+ * completing the split here as it is not possible that a re-split of new
+ * bucket starts when there is still a pending split from old bucket.
+ */
+ if (H_BUCKET_BEING_SPLIT(oopaque))
+ {
+ /*
+ * Copy bucket mapping info now; refer the comment in code below where
+ * we copy this information before calling _hash_splitbucket to see
+ * why this is okay.
+ */
+ maxbucket = metap->hashm_maxbucket;
+ highmask = metap->hashm_highmask;
+ lowmask = metap->hashm_lowmask;
+
+ /*
+ * Release the lock on metapage and old_bucket, before completing the
+ * split.
+ */
+ LockBuffer(metabuf, BUFFER_LOCK_UNLOCK);
+ LockBuffer(buf_oblkno, BUFFER_LOCK_UNLOCK);
+
+ _hash_finish_split(rel, metabuf, buf_oblkno, old_bucket, maxbucket,
+ highmask, lowmask);
+
+ /* release the pin on old buffer and retry for expand. */
+ _hash_dropbuf(rel, buf_oblkno);
+
+ goto restart_expand;
+ }
+
+ /*
+ * Clean the tuples remained from the previous split. This operation
+ * requires cleanup lock and we already have one on the old bucket, so
+ * let's do it. We also don't want to allow further splits from the bucket
+ * till the garbage of previous split is cleaned. This has two
+ * advantages; first, it helps in avoiding the bloat due to garbage and
+ * second is, during cleanup of bucket, we are always sure that the
+ * garbage tuples belong to most recently split bucket. On the contrary,
+ * if we allow cleanup of bucket after meta page is updated to indicate
+ * the new split and before the actual split, the cleanup operation won't
+ * be able to decide whether the tuple has been moved to the newly created
+ * bucket and ended up deleting such tuples.
+ */
+ if (H_NEEDS_SPLIT_CLEANUP(oopaque))
+ {
+ /*
+ * Copy bucket mapping info now; refer to the comment in code below
+ * where we copy this information before calling _hash_splitbucket to
+ * see why this is okay.
+ */
+ maxbucket = metap->hashm_maxbucket;
+ highmask = metap->hashm_highmask;
+ lowmask = metap->hashm_lowmask;
+
+ /* Release the metapage lock. */
+ LockBuffer(metabuf, BUFFER_LOCK_UNLOCK);
+
+ hashbucketcleanup(rel, old_bucket, buf_oblkno, start_oblkno, NULL,
+ maxbucket, highmask, lowmask, NULL, NULL, true,
+ NULL, NULL);
+
+ _hash_dropbuf(rel, buf_oblkno);
+
+ goto restart_expand;
+ }
+
+ /*
+ * There shouldn't be any active scan on new bucket.
*
* 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
*/
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.
+ * If the split point is increasing we need to allocate a new batch of
+ * bucket pages.
*/
- spare_ndx = _hash_log2(new_bucket + 1);
+ spare_ndx = _hash_spareindex(new_bucket + 1);
if (spare_ndx > metap->hashm_ovflpoint)
{
+ uint32 buckets_to_add;
+
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.
+ * We treat allocation of buckets as a separate WAL-logged action.
+ * Even if we fail after this operation, won't leak bucket pages;
+ * rather, the next split will consume this space. In any case, even
+ * without failure we don't use all the space in one split operation.
*/
- if (!_hash_alloc_buckets(rel, start_nblkno, new_bucket))
+ buckets_to_add = _hash_get_totalbuckets(spare_ndx) - new_bucket;
+ if (!_hash_alloc_buckets(rel, start_nblkno, buckets_to_add))
{
/* can't split due to BlockNumber overflow */
- _hash_droplock(rel, start_oblkno, HASH_EXCLUSIVE);
- _hash_droplock(rel, start_nblkno, HASH_EXCLUSIVE);
+ _hash_relbuf(rel, buf_oblkno);
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
+ * Physically allocate the new bucket's primary page. We want to do this
+ * before changing the metapage's mapping info, in case we can't get the
+ * disk space. Ideally, we don't need to check for cleanup lock on new
+ * bucket as no other backend could find this bucket unless meta page is
+ * updated. However, it is good to be consistent with old bucket locking.
+ */
+ buf_nblkno = _hash_getnewbuf(rel, start_nblkno, MAIN_FORKNUM);
+ if (!IsBufferCleanupOK(buf_nblkno))
+ {
+ _hash_relbuf(rel, buf_oblkno);
+ _hash_relbuf(rel, buf_nblkno);
+ goto fail;
+ }
+
+ /*
+ * Since we are scribbling on the pages in the shared buffers, establish a
+ * critical section. Any failure in this next code leaves us with a big
* problem: the metapage is effectively corrupt but could get written back
- * to disk. We don't really expect any failure, but just to be sure,
- * establish a critical section.
+ * to disk.
*/
START_CRIT_SECTION();
+ /*
+ * Okay to proceed with split. Update the metapage bucket mapping info.
+ */
metap->hashm_maxbucket = new_bucket;
if (new_bucket > metap->hashm_highmask)
/* Starting a new doubling */
metap->hashm_lowmask = metap->hashm_highmask;
metap->hashm_highmask = new_bucket | metap->hashm_lowmask;
+ metap_update_masks = true;
}
/*
- * 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.
+ * If the split point is increasing 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.
*/
if (spare_ndx > metap->hashm_ovflpoint)
{
metap->hashm_spares[spare_ndx] = metap->hashm_spares[metap->hashm_ovflpoint];
metap->hashm_ovflpoint = spare_ndx;
+ metap_update_splitpoint = true;
}
- /* Done mucking with metapage */
- END_CRIT_SECTION();
+ MarkBufferDirty(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
+ * 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;
lowmask = metap->hashm_lowmask;
- /* Write out the metapage and drop lock, but keep pin */
- _hash_chgbufaccess(rel, metabuf, HASH_WRITE, HASH_NOLOCK);
+ opage = BufferGetPage(buf_oblkno);
+ oopaque = (HashPageOpaque) PageGetSpecialPointer(opage);
+
+ /*
+ * Mark the old bucket to indicate that split is in progress. (At
+ * operation end, we will clear the split-in-progress flag.) Also, for a
+ * primary bucket page, hasho_prevblkno stores the number of buckets that
+ * existed as of the last split, so we must update that value here.
+ */
+ oopaque->hasho_flag |= LH_BUCKET_BEING_SPLIT;
+ oopaque->hasho_prevblkno = maxbucket;
+
+ MarkBufferDirty(buf_oblkno);
+
+ npage = BufferGetPage(buf_nblkno);
+
+ /*
+ * initialize the new bucket's primary page and mark it to indicate that
+ * split is in progress.
+ */
+ nopaque = (HashPageOpaque) PageGetSpecialPointer(npage);
+ nopaque->hasho_prevblkno = maxbucket;
+ nopaque->hasho_nextblkno = InvalidBlockNumber;
+ nopaque->hasho_bucket = new_bucket;
+ nopaque->hasho_flag = LH_BUCKET_PAGE | LH_BUCKET_BEING_POPULATED;
+ nopaque->hasho_page_id = HASHO_PAGE_ID;
+
+ MarkBufferDirty(buf_nblkno);
+
+ /* XLOG stuff */
+ if (RelationNeedsWAL(rel))
+ {
+ xl_hash_split_allocate_page xlrec;
+ XLogRecPtr recptr;
+
+ xlrec.new_bucket = maxbucket;
+ xlrec.old_bucket_flag = oopaque->hasho_flag;
+ xlrec.new_bucket_flag = nopaque->hasho_flag;
+ xlrec.flags = 0;
+
+ XLogBeginInsert();
+
+ XLogRegisterBuffer(0, buf_oblkno, REGBUF_STANDARD);
+ XLogRegisterBuffer(1, buf_nblkno, REGBUF_WILL_INIT);
+ XLogRegisterBuffer(2, metabuf, REGBUF_STANDARD);
+
+ if (metap_update_masks)
+ {
+ xlrec.flags |= XLH_SPLIT_META_UPDATE_MASKS;
+ XLogRegisterBufData(2, (char *) &metap->hashm_lowmask, sizeof(uint32));
+ XLogRegisterBufData(2, (char *) &metap->hashm_highmask, sizeof(uint32));
+ }
+
+ if (metap_update_splitpoint)
+ {
+ xlrec.flags |= XLH_SPLIT_META_UPDATE_SPLITPOINT;
+ XLogRegisterBufData(2, (char *) &metap->hashm_ovflpoint,
+ sizeof(uint32));
+ XLogRegisterBufData(2,
+ (char *) &metap->hashm_spares[metap->hashm_ovflpoint],
+ sizeof(uint32));
+ }
+
+ XLogRegisterData((char *) &xlrec, SizeOfHashSplitAllocPage);
- /* Release split lock; okay for other splits to occur now */
- _hash_droplock(rel, 0, HASH_EXCLUSIVE);
+ recptr = XLogInsert(RM_HASH_ID, XLOG_HASH_SPLIT_ALLOCATE_PAGE);
+
+ PageSetLSN(BufferGetPage(buf_oblkno), recptr);
+ PageSetLSN(BufferGetPage(buf_nblkno), recptr);
+ PageSetLSN(BufferGetPage(metabuf), recptr);
+ }
+
+ END_CRIT_SECTION();
+
+ /* drop lock, but keep pin */
+ LockBuffer(metabuf, BUFFER_LOCK_UNLOCK);
/* Relocate records to the new bucket */
- _hash_splitbucket(rel, metabuf, old_bucket, new_bucket,
- start_oblkno, start_nblkno,
+ _hash_splitbucket(rel, metabuf,
+ old_bucket, new_bucket,
+ buf_oblkno, buf_nblkno, NULL,
maxbucket, highmask, lowmask);
- /* Release bucket locks, allowing others to access them */
- _hash_droplock(rel, start_oblkno, HASH_EXCLUSIVE);
- _hash_droplock(rel, start_nblkno, HASH_EXCLUSIVE);
+ /* all done, now release the pins on primary buckets. */
+ _hash_dropbuf(rel, buf_oblkno);
+ _hash_dropbuf(rel, buf_nblkno);
return;
fail:
/* 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);
+ LockBuffer(metabuf, BUFFER_LOCK_UNLOCK);
}
* 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
+ * We need to interlock against _hash_addovflpage() 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.
{
BlockNumber lastblock;
char zerobuf[BLCKSZ];
+ Page page;
+ HashPageOpaque ovflopaque;
lastblock = firstblock + nblocks - 1;
if (lastblock < firstblock || lastblock == InvalidBlockNumber)
return false;
- MemSet(zerobuf, 0, sizeof(zerobuf));
+ page = (Page) zerobuf;
+
+ /*
+ * Initialize the page. Just zeroing the page won't work; see
+ * _hash_freeovflpage for similar usage. We take care to make the special
+ * space valid for the benefit of tools such as pageinspect.
+ */
+ _hash_pageinit(page, BLCKSZ);
+
+ ovflopaque = (HashPageOpaque) PageGetSpecialPointer(page);
+
+ ovflopaque->hasho_prevblkno = InvalidBlockNumber;
+ ovflopaque->hasho_nextblkno = InvalidBlockNumber;
+ ovflopaque->hasho_bucket = -1;
+ ovflopaque->hasho_flag = LH_UNUSED_PAGE;
+ ovflopaque->hasho_page_id = HASHO_PAGE_ID;
+
+ if (RelationNeedsWAL(rel))
+ log_newpage(&rel->rd_node,
+ MAIN_FORKNUM,
+ lastblock,
+ zerobuf,
+ true);
RelationOpenSmgr(rel);
- smgrextend(rel->rd_smgr, MAIN_FORKNUM, lastblock, zerobuf, rel->rd_istemp);
+ smgrextend(rel->rd_smgr, MAIN_FORKNUM, lastblock, zerobuf, false);
return true;
}
/*
* _hash_splitbucket -- split 'obucket' into 'obucket' and 'nbucket'
*
+ * This routine is used to partition the tuples between old and new bucket and
+ * is used to finish the incomplete split operations. To finish the previously
+ * interrupted split operation, the caller needs to fill htab. If htab is set,
+ * then we skip the movement of tuples that exists in htab, otherwise NULL
+ * value of htab indicates movement of all the tuples that belong to the new
+ * bucket.
+ *
* We are splitting a bucket that consists of a base bucket page and zero
* or more overflow (bucket chain) pages. We must relocate tuples that
- * belong in the new bucket, and compress out any free space in the old
- * bucket.
+ * belong in the new bucket.
*
- * The caller must hold exclusive locks on both buckets to ensure that
+ * The caller must hold cleanup locks on both buckets to ensure that
* no one else is trying to access them (see README).
*
* The caller must hold a pin, but no lock, on the metapage buffer.
* The buffer is returned in the same state. (The metapage is only
* touched if it becomes necessary to add or remove overflow pages.)
+ *
+ * Split needs to retain pin on primary bucket pages of both old and new
+ * buckets till end of operation. This is to prevent vacuum from starting
+ * while a split is in progress.
+ *
+ * In addition, the caller must have created the new bucket's base page,
+ * which is passed in buffer nbuf, pinned and write-locked. The lock will be
+ * released here and pin must be released by the caller. (The API is set up
+ * this way because we must do _hash_getnewbuf() before releasing the metapage
+ * write lock. So instead of passing the new bucket's start block number, we
+ * pass an actual buffer.)
*/
static void
_hash_splitbucket(Relation rel,
Buffer metabuf,
Bucket obucket,
Bucket nbucket,
- BlockNumber start_oblkno,
- BlockNumber start_nblkno,
+ Buffer obuf,
+ Buffer nbuf,
+ HTAB *htab,
uint32 maxbucket,
uint32 highmask,
uint32 lowmask)
{
- Bucket bucket;
- Buffer obuf;
- Buffer nbuf;
- BlockNumber oblkno;
- BlockNumber nblkno;
- bool null;
- Datum datum;
- HashPageOpaque oopaque;
- HashPageOpaque nopaque;
- IndexTuple itup;
- Size itemsz;
- OffsetNumber ooffnum;
- OffsetNumber noffnum;
- OffsetNumber omaxoffnum;
+ Buffer bucket_obuf;
+ Buffer bucket_nbuf;
Page opage;
Page npage;
- TupleDesc itupdesc = RelationGetDescr(rel);
+ HashPageOpaque oopaque;
+ HashPageOpaque nopaque;
+ OffsetNumber itup_offsets[MaxIndexTuplesPerPage];
+ IndexTuple itups[MaxIndexTuplesPerPage];
+ Size all_tups_size = 0;
+ int i;
+ uint16 nitups = 0;
- /*
- * 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.
- */
- oblkno = start_oblkno;
- obuf = _hash_getbuf(rel, oblkno, HASH_WRITE, LH_BUCKET_PAGE);
+ bucket_obuf = obuf;
opage = BufferGetPage(obuf);
oopaque = (HashPageOpaque) PageGetSpecialPointer(opage);
- nblkno = start_nblkno;
- nbuf = _hash_getnewbuf(rel, nblkno);
+ bucket_nbuf = nbuf;
npage = BufferGetPage(nbuf);
-
- /* initialize the new bucket's primary page */
nopaque = (HashPageOpaque) PageGetSpecialPointer(npage);
- nopaque->hasho_prevblkno = InvalidBlockNumber;
- nopaque->hasho_nextblkno = InvalidBlockNumber;
- nopaque->hasho_bucket = nbucket;
- nopaque->hasho_flag = LH_BUCKET_PAGE;
- 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)
+ BlockNumber oblkno;
+ OffsetNumber ooffnum;
+ OffsetNumber omaxoffnum;
+
+ /* 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;
+ bool found = false;
+
+ /* skip dead tuples */
+ if (ItemIdIsDead(PageGetItemId(opage, ooffnum)))
+ continue;
/*
- * we ran out of tuples on this particular page, but we have more
- * overflow pages; advance to next page.
+ * Before inserting a tuple, probe the hash table containing TIDs
+ * of tuples belonging to new bucket, if we find a match, then
+ * skip that tuple, else fetch the item's hash key (conveniently
+ * stored in the item) and determine which bucket it now belongs
+ * in.
*/
- _hash_wrtbuf(rel, obuf);
-
- obuf = _hash_getbuf(rel, oblkno, HASH_WRITE, LH_OVERFLOW_PAGE);
- opage = BufferGetPage(obuf);
- oopaque = (HashPageOpaque) PageGetSpecialPointer(opage);
- ooffnum = FirstOffsetNumber;
- omaxoffnum = PageGetMaxOffsetNumber(opage);
- continue;
- }
+ itup = (IndexTuple) PageGetItem(opage,
+ PageGetItemId(opage, ooffnum));
- /*
- * 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.
- */
- itup = (IndexTuple) PageGetItem(opage, PageGetItemId(opage, ooffnum));
- datum = index_getattr(itup, 1, itupdesc, &null);
- Assert(!null);
+ if (htab)
+ (void) hash_search(htab, &itup->t_tid, HASH_FIND, &found);
- bucket = _hash_hashkey2bucket(_hash_datum2hashkey(rel, datum),
- maxbucket, highmask, lowmask);
+ if (found)
+ 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);
+ bucket = _hash_hashkey2bucket(_hash_get_indextuple_hashkey(itup),
+ maxbucket, highmask, lowmask);
- if (PageGetFreeSpace(npage) < itemsz)
+ if (bucket == nbucket)
{
- /* 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 nopaque within the loop */
+ IndexTuple new_itup;
+
+ /*
+ * make a copy of index tuple as we have to scribble on it.
+ */
+ new_itup = CopyIndexTuple(itup);
+
+ /*
+ * mark the index tuple as moved by split, such tuples are
+ * skipped by scan if there is split in progress for a bucket.
+ */
+ new_itup->t_info |= INDEX_MOVED_BY_SPLIT_MASK;
+
+ /*
+ * 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(*new_itup);
+ itemsz = MAXALIGN(itemsz);
+
+ if (PageGetFreeSpaceForMultipleTuples(npage, nitups + 1) < (all_tups_size + itemsz))
+ {
+ /*
+ * Change the shared buffer state in critical section,
+ * otherwise any error could make it unrecoverable.
+ */
+ START_CRIT_SECTION();
+
+ _hash_pgaddmultitup(rel, nbuf, itups, itup_offsets, nitups);
+ MarkBufferDirty(nbuf);
+ /* log the split operation before releasing the lock */
+ log_split_page(rel, nbuf);
+
+ END_CRIT_SECTION();
+
+ /* drop lock, but keep pin */
+ LockBuffer(nbuf, BUFFER_LOCK_UNLOCK);
+
+ /* be tidy */
+ for (i = 0; i < nitups; i++)
+ pfree(itups[i]);
+ nitups = 0;
+ all_tups_size = 0;
+
+ /* chain to a new overflow page */
+ nbuf = _hash_addovflpage(rel, metabuf, nbuf, (nbuf == bucket_nbuf) ? true : false);
+ npage = BufferGetPage(nbuf);
+ nopaque = (HashPageOpaque) PageGetSpecialPointer(npage);
+ }
+
+ itups[nitups++] = new_itup;
+ all_tups_size += itemsz;
}
+ else
+ {
+ /*
+ * the tuple stays on this page, so nothing to do.
+ */
+ Assert(bucket == obucket);
+ }
+ }
- noffnum = OffsetNumberNext(PageGetMaxOffsetNumber(npage));
- if (PageAddItem(npage, (Item) itup, itemsz, noffnum, false, false)
- == InvalidOffsetNumber)
- elog(ERROR, "failed to add index item to \"%s\"",
- RelationGetRelationName(rel));
+ oblkno = oopaque->hasho_nextblkno;
- /*
- * 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);
- }
+ /* retain the pin on the old primary bucket */
+ if (obuf == bucket_obuf)
+ LockBuffer(obuf, BUFFER_LOCK_UNLOCK);
else
+ _hash_relbuf(rel, obuf);
+
+ /* Exit loop if no more overflow pages in old bucket */
+ if (!BlockNumberIsValid(oblkno))
{
/*
- * 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'.
+ * Change the shared buffer state in critical section, otherwise
+ * any error could make it unrecoverable.
*/
- Assert(bucket == obucket);
- ooffnum = OffsetNumberNext(ooffnum);
+ START_CRIT_SECTION();
+
+ _hash_pgaddmultitup(rel, nbuf, itups, itup_offsets, nitups);
+ MarkBufferDirty(nbuf);
+ /* log the split operation before releasing the lock */
+ log_split_page(rel, nbuf);
+
+ END_CRIT_SECTION();
+
+ if (nbuf == bucket_nbuf)
+ LockBuffer(nbuf, BUFFER_LOCK_UNLOCK);
+ else
+ _hash_relbuf(rel, nbuf);
+
+ /* be tidy */
+ for (i = 0; i < nitups; i++)
+ pfree(itups[i]);
+ break;
}
+
+ /* Else, advance to next old page */
+ obuf = _hash_getbuf(rel, oblkno, HASH_READ, 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
- * tuples remaining in the old bucket (including the overflow pages) are
- * packed as tightly as possible. The new bucket is already tight.
+ * the tuples. Mark the old and new buckets to indicate split is
+ * finished.
+ *
+ * To avoid deadlocks due to locking order of buckets, first lock the old
+ * bucket and then the new bucket.
*/
- _hash_wrtbuf(rel, obuf);
- _hash_wrtbuf(rel, nbuf);
+ LockBuffer(bucket_obuf, BUFFER_LOCK_EXCLUSIVE);
+ opage = BufferGetPage(bucket_obuf);
+ oopaque = (HashPageOpaque) PageGetSpecialPointer(opage);
+
+ LockBuffer(bucket_nbuf, BUFFER_LOCK_EXCLUSIVE);
+ npage = BufferGetPage(bucket_nbuf);
+ nopaque = (HashPageOpaque) PageGetSpecialPointer(npage);
- _hash_squeezebucket(rel, obucket, start_oblkno, NULL);
+ START_CRIT_SECTION();
+
+ oopaque->hasho_flag &= ~LH_BUCKET_BEING_SPLIT;
+ nopaque->hasho_flag &= ~LH_BUCKET_BEING_POPULATED;
+
+ /*
+ * After the split is finished, mark the old bucket to indicate that it
+ * contains deletable tuples. We will clear split-cleanup flag after
+ * deleting such tuples either at the end of split or at the next split
+ * from old bucket or at the time of vacuum.
+ */
+ oopaque->hasho_flag |= LH_BUCKET_NEEDS_SPLIT_CLEANUP;
+
+ /*
+ * now write the buffers, here we don't release the locks as caller is
+ * responsible to release locks.
+ */
+ MarkBufferDirty(bucket_obuf);
+ MarkBufferDirty(bucket_nbuf);
+
+ if (RelationNeedsWAL(rel))
+ {
+ XLogRecPtr recptr;
+ xl_hash_split_complete xlrec;
+
+ xlrec.old_bucket_flag = oopaque->hasho_flag;
+ xlrec.new_bucket_flag = nopaque->hasho_flag;
+
+ XLogBeginInsert();
+
+ XLogRegisterData((char *) &xlrec, SizeOfHashSplitComplete);
+
+ XLogRegisterBuffer(0, bucket_obuf, REGBUF_STANDARD);
+ XLogRegisterBuffer(1, bucket_nbuf, REGBUF_STANDARD);
+
+ recptr = XLogInsert(RM_HASH_ID, XLOG_HASH_SPLIT_COMPLETE);
+
+ PageSetLSN(BufferGetPage(bucket_obuf), recptr);
+ PageSetLSN(BufferGetPage(bucket_nbuf), recptr);
+ }
+
+ END_CRIT_SECTION();
+
+ /*
+ * If possible, clean up the old bucket. We might not be able to do this
+ * if someone else has a pin on it, but if not then we can go ahead. This
+ * isn't absolutely necessary, but it reduces bloat; if we don't do it
+ * now, VACUUM will do it eventually, but maybe not until new overflow
+ * pages have been allocated. Note that there's no need to clean up the
+ * new bucket.
+ */
+ if (IsBufferCleanupOK(bucket_obuf))
+ {
+ LockBuffer(bucket_nbuf, BUFFER_LOCK_UNLOCK);
+ hashbucketcleanup(rel, obucket, bucket_obuf,
+ BufferGetBlockNumber(bucket_obuf), NULL,
+ maxbucket, highmask, lowmask, NULL, NULL, true,
+ NULL, NULL);
+ }
+ else
+ {
+ LockBuffer(bucket_nbuf, BUFFER_LOCK_UNLOCK);
+ LockBuffer(bucket_obuf, BUFFER_LOCK_UNLOCK);
+ }
+}
+
+/*
+ * _hash_finish_split() -- Finish the previously interrupted split operation
+ *
+ * To complete the split operation, we form the hash table of TIDs in new
+ * bucket which is then used by split operation to skip tuples that are
+ * already moved before the split operation was previously interrupted.
+ *
+ * The caller must hold a pin, but no lock, on the metapage and old bucket's
+ * primary page buffer. The buffers are returned in the same state. (The
+ * metapage is only touched if it becomes necessary to add or remove overflow
+ * pages.)
+ */
+void
+_hash_finish_split(Relation rel, Buffer metabuf, Buffer obuf, Bucket obucket,
+ uint32 maxbucket, uint32 highmask, uint32 lowmask)
+{
+ HASHCTL hash_ctl;
+ HTAB *tidhtab;
+ Buffer bucket_nbuf = InvalidBuffer;
+ Buffer nbuf;
+ Page npage;
+ BlockNumber nblkno;
+ BlockNumber bucket_nblkno;
+ HashPageOpaque npageopaque;
+ Bucket nbucket;
+ bool found;
+
+ /* Initialize hash tables used to track TIDs */
+ memset(&hash_ctl, 0, sizeof(hash_ctl));
+ hash_ctl.keysize = sizeof(ItemPointerData);
+ hash_ctl.entrysize = sizeof(ItemPointerData);
+ hash_ctl.hcxt = CurrentMemoryContext;
+
+ tidhtab =
+ hash_create("bucket ctids",
+ 256, /* arbitrary initial size */
+ &hash_ctl,
+ HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
+
+ bucket_nblkno = nblkno = _hash_get_newblock_from_oldbucket(rel, obucket);
+
+ /*
+ * Scan the new bucket and build hash table of TIDs
+ */
+ for (;;)
+ {
+ OffsetNumber noffnum;
+ OffsetNumber nmaxoffnum;
+
+ nbuf = _hash_getbuf(rel, nblkno, HASH_READ,
+ LH_BUCKET_PAGE | LH_OVERFLOW_PAGE);
+
+ /* remember the primary bucket buffer to acquire cleanup lock on it. */
+ if (nblkno == bucket_nblkno)
+ bucket_nbuf = nbuf;
+
+ npage = BufferGetPage(nbuf);
+ npageopaque = (HashPageOpaque) PageGetSpecialPointer(npage);
+
+ /* Scan each tuple in new page */
+ nmaxoffnum = PageGetMaxOffsetNumber(npage);
+ for (noffnum = FirstOffsetNumber;
+ noffnum <= nmaxoffnum;
+ noffnum = OffsetNumberNext(noffnum))
+ {
+ IndexTuple itup;
+
+ /* Fetch the item's TID and insert it in hash table. */
+ itup = (IndexTuple) PageGetItem(npage,
+ PageGetItemId(npage, noffnum));
+
+ (void) hash_search(tidhtab, &itup->t_tid, HASH_ENTER, &found);
+
+ Assert(!found);
+ }
+
+ nblkno = npageopaque->hasho_nextblkno;
+
+ /*
+ * release our write lock without modifying buffer and ensure to
+ * retain the pin on primary bucket.
+ */
+ if (nbuf == bucket_nbuf)
+ LockBuffer(nbuf, BUFFER_LOCK_UNLOCK);
+ else
+ _hash_relbuf(rel, nbuf);
+
+ /* Exit loop if no more overflow pages in new bucket */
+ if (!BlockNumberIsValid(nblkno))
+ break;
+ }
+
+ /*
+ * Conditionally get the cleanup lock on old and new buckets to perform
+ * the split operation. If we don't get the cleanup locks, silently give
+ * up and next insertion on old bucket will try again to complete the
+ * split.
+ */
+ if (!ConditionalLockBufferForCleanup(obuf))
+ {
+ hash_destroy(tidhtab);
+ return;
+ }
+ if (!ConditionalLockBufferForCleanup(bucket_nbuf))
+ {
+ LockBuffer(obuf, BUFFER_LOCK_UNLOCK);
+ hash_destroy(tidhtab);
+ return;
+ }
+
+ npage = BufferGetPage(bucket_nbuf);
+ npageopaque = (HashPageOpaque) PageGetSpecialPointer(npage);
+ nbucket = npageopaque->hasho_bucket;
+
+ _hash_splitbucket(rel, metabuf, obucket,
+ nbucket, obuf, bucket_nbuf, tidhtab,
+ maxbucket, highmask, lowmask);
+
+ _hash_dropbuf(rel, bucket_nbuf);
+ hash_destroy(tidhtab);
+}
+
+/*
+ * log_split_page() -- Log the split operation
+ *
+ * We log the split operation when the new page in new bucket gets full,
+ * so we log the entire page.
+ *
+ * 'buf' must be locked by the caller which is also responsible for unlocking
+ * it.
+ */
+static void
+log_split_page(Relation rel, Buffer buf)
+{
+ if (RelationNeedsWAL(rel))
+ {
+ XLogRecPtr recptr;
+
+ XLogBeginInsert();
+
+ XLogRegisterBuffer(0, buf, REGBUF_FORCE_IMAGE | REGBUF_STANDARD);
+
+ recptr = XLogInsert(RM_HASH_ID, XLOG_HASH_SPLIT_PAGE);
+
+ PageSetLSN(BufferGetPage(buf), recptr);
+ }
+}
+
+/*
+ * _hash_getcachedmetap() -- Returns cached metapage data.
+ *
+ * If metabuf is not InvalidBuffer, caller must hold a pin, but no lock, on
+ * the metapage. If not set, we'll set it before returning if we have to
+ * refresh the cache, and return with a pin but no lock on it; caller is
+ * responsible for releasing the pin.
+ *
+ * We refresh the cache if it's not initialized yet or force_refresh is true.
+ */
+HashMetaPage
+_hash_getcachedmetap(Relation rel, Buffer *metabuf, bool force_refresh)
+{
+ Page page;
+
+ Assert(metabuf);
+ if (force_refresh || rel->rd_amcache == NULL)
+ {
+ char *cache = NULL;
+
+ /*
+ * It's important that we don't set rd_amcache to an invalid value.
+ * Either MemoryContextAlloc or _hash_getbuf could fail, so don't
+ * install a pointer to the newly-allocated storage in the actual
+ * relcache entry until both have succeeeded.
+ */
+ if (rel->rd_amcache == NULL)
+ cache = MemoryContextAlloc(rel->rd_indexcxt,
+ sizeof(HashMetaPageData));
+
+ /* Read the metapage. */
+ if (BufferIsValid(*metabuf))
+ LockBuffer(*metabuf, BUFFER_LOCK_SHARE);
+ else
+ *metabuf = _hash_getbuf(rel, HASH_METAPAGE, HASH_READ,
+ LH_META_PAGE);
+ page = BufferGetPage(*metabuf);
+
+ /* Populate the cache. */
+ if (rel->rd_amcache == NULL)
+ rel->rd_amcache = cache;
+ memcpy(rel->rd_amcache, HashPageGetMeta(page),
+ sizeof(HashMetaPageData));
+
+ /* Release metapage lock, but keep the pin. */
+ LockBuffer(*metabuf, BUFFER_LOCK_UNLOCK);
+ }
+
+ return (HashMetaPage) rel->rd_amcache;
+}
+
+/*
+ * _hash_getbucketbuf_from_hashkey() -- Get the bucket's buffer for the given
+ * hashkey.
+ *
+ * Bucket pages do not move or get removed once they are allocated. This give
+ * us an opportunity to use the previously saved metapage contents to reach
+ * the target bucket buffer, instead of reading from the metapage every time.
+ * This saves one buffer access every time we want to reach the target bucket
+ * buffer, which is very helpful savings in bufmgr traffic and contention.
+ *
+ * The access type parameter (HASH_READ or HASH_WRITE) indicates whether the
+ * bucket buffer has to be locked for reading or writing.
+ *
+ * The out parameter cachedmetap is set with metapage contents used for
+ * hashkey to bucket buffer mapping. Some callers need this info to reach the
+ * old bucket in case of bucket split, see _hash_doinsert().
+ */
+Buffer
+_hash_getbucketbuf_from_hashkey(Relation rel, uint32 hashkey, int access,
+ HashMetaPage *cachedmetap)
+{
+ HashMetaPage metap;
+ Buffer buf;
+ Buffer metabuf = InvalidBuffer;
+ Page page;
+ Bucket bucket;
+ BlockNumber blkno;
+ HashPageOpaque opaque;
+
+ /* We read from target bucket buffer, hence locking is must. */
+ Assert(access == HASH_READ || access == HASH_WRITE);
+
+ metap = _hash_getcachedmetap(rel, &metabuf, false);
+ Assert(metap != NULL);
+
+ /*
+ * Loop until we get a lock on the correct target bucket.
+ */
+ for (;;)
+ {
+ /*
+ * Compute the target bucket number, and convert to block number.
+ */
+ bucket = _hash_hashkey2bucket(hashkey,
+ metap->hashm_maxbucket,
+ metap->hashm_highmask,
+ metap->hashm_lowmask);
+
+ blkno = BUCKET_TO_BLKNO(metap, bucket);
+
+ /* Fetch the primary bucket page for the bucket */
+ buf = _hash_getbuf(rel, blkno, access, LH_BUCKET_PAGE);
+ page = BufferGetPage(buf);
+ opaque = (HashPageOpaque) PageGetSpecialPointer(page);
+ Assert(opaque->hasho_bucket == bucket);
+ Assert(opaque->hasho_prevblkno != InvalidBlockNumber);
+
+ /*
+ * If this bucket hasn't been split, we're done.
+ */
+ if (opaque->hasho_prevblkno <= metap->hashm_maxbucket)
+ break;
+
+ /* Drop lock on this buffer, update cached metapage, and retry. */
+ _hash_relbuf(rel, buf);
+ metap = _hash_getcachedmetap(rel, &metabuf, true);
+ Assert(metap != NULL);
+ }
+
+ if (BufferIsValid(metabuf))
+ _hash_dropbuf(rel, metabuf);
+
+ if (cachedmetap)
+ *cachedmetap = metap;
+
+ return buf;
}
projects / postgresql / blobdiff