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/*-------------------------------------------------------------------------
*
* hashutil.c
* Utility code for Postgres hash implementation.
*
* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/access/hash/hashutil.c,v 1.35 2003/09/02 18:13:31 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/genam.h"
#include "access/hash.h"
#include "access/iqual.h"
/*
* _hash_mkscankey -- build a scan key matching the given indextuple
*
* Note: this is prepared for multiple index columns, but very little
* else in access/hash is ...
*/
ScanKey
_hash_mkscankey(Relation rel, IndexTuple itup)
{
ScanKey skey;
TupleDesc itupdesc = RelationGetDescr(rel);
int natts = rel->rd_rel->relnatts;
AttrNumber i;
Datum arg;
FmgrInfo *procinfo;
bool isnull;
skey = (ScanKey) palloc(natts * sizeof(ScanKeyData));
for (i = 0; i < natts; i++)
{
arg = index_getattr(itup, i + 1, itupdesc, &isnull);
procinfo = index_getprocinfo(rel, i + 1, HASHPROC);
ScanKeyEntryInitializeWithInfo(&skey[i],
isnull ? SK_ISNULL : 0x0,
(AttrNumber) (i + 1),
procinfo,
CurrentMemoryContext,
arg);
}
return skey;
}
void
_hash_freeskey(ScanKey skey)
{
pfree(skey);
}
/*
* _hash_checkqual -- does the index tuple satisfy the scan conditions?
*/
bool
_hash_checkqual(IndexScanDesc scan, IndexTuple itup)
{
return index_keytest(itup, RelationGetDescr(scan->indexRelation),
scan->numberOfKeys, scan->keyData);
}
/*
* _hash_formitem -- construct a hash index entry
*/
HashItem
_hash_formitem(IndexTuple itup)
{
int nbytes_hitem;
HashItem hitem;
Size tuplen;
/* disallow nulls in hash keys */
if (IndexTupleHasNulls(itup))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("hash indexes cannot include null keys")));
/*
* make a copy of the index tuple (XXX do we still need to copy?)
*
* HashItemData used to have more fields than IndexTupleData, but no
* longer...
*/
tuplen = IndexTupleSize(itup);
nbytes_hitem = tuplen +
(sizeof(HashItemData) - sizeof(IndexTupleData));
hitem = (HashItem) palloc(nbytes_hitem);
memcpy((char *) &(hitem->hash_itup), (char *) itup, tuplen);
return hitem;
}
/*
* _hash_call -- given a Datum, call the index's hash procedure
*
* Returns the bucket number that the hash key maps to.
*/
Bucket
_hash_call(Relation rel, HashMetaPage metap, Datum key)
{
FmgrInfo *procinfo;
uint32 n;
Bucket bucket;
/* XXX assumes index has only one attribute */
procinfo = index_getprocinfo(rel, 1, HASHPROC);
n = DatumGetUInt32(FunctionCall1(procinfo, key));
bucket = n & metap->hashm_highmask;
if (bucket > metap->hashm_maxbucket)
bucket = bucket & metap->hashm_lowmask;
return bucket;
}
/*
* _hash_log2 -- returns ceil(lg2(num))
*/
uint32
_hash_log2(uint32 num)
{
uint32 i,
limit;
limit = 1;
for (i = 0; limit < num; limit <<= 1, i++)
;
return i;
}
/*
* _hash_checkpage -- sanity checks on the format of all hash pages
*/
void
_hash_checkpage(Relation rel, Page page, int flags)
{
Assert(page);
/*
* When checking the metapage, always verify magic number and version.
*/
if (flags == LH_META_PAGE)
{
HashMetaPage metap = (HashMetaPage) page;
if (metap->hashm_magic != HASH_MAGIC)
ereport(ERROR,
(errcode(ERRCODE_INDEX_CORRUPTED),
errmsg("index \"%s\" is not a hash index",
RelationGetRelationName(rel))));
if (metap->hashm_version != HASH_VERSION)
ereport(ERROR,
(errcode(ERRCODE_INDEX_CORRUPTED),
errmsg("index \"%s\" has wrong hash version, please REINDEX it",
RelationGetRelationName(rel))));
}
/*
* These other checks are for debugging purposes only.
*/
#ifdef USE_ASSERT_CHECKING
Assert(((PageHeader) (page))->pd_lower >= SizeOfPageHeaderData);
Assert(((PageHeader) (page))->pd_upper <=
(BLCKSZ - MAXALIGN(sizeof(HashPageOpaqueData))));
Assert(((PageHeader) (page))->pd_special ==
(BLCKSZ - MAXALIGN(sizeof(HashPageOpaqueData))));
Assert(PageGetPageSize(page) == BLCKSZ);
if (flags)
{
HashPageOpaque opaque = (HashPageOpaque) PageGetSpecialPointer(page);
Assert(opaque->hasho_flag & flags);
}
#endif /* USE_ASSERT_CHECKING */
}
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