gistutil.c

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/*-------------------------------------------------------------------------
 *
 * gistutil.c
 *	  utilities routines for the postgres GiST index access method.
 *
 *
 * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *			$PostgreSQL: pgsql/src/backend/access/gist/gistutil.c,v 1.25 2008/01/01 19:45:46 momjian Exp $
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/gist_private.h"
#include "access/heapam.h"
#include "access/reloptions.h"
#include "storage/freespace.h"

/*
 * static *S used for temrorary storage (saves stack and palloc() call)
 */

static Datum attrS[INDEX_MAX_KEYS];
static bool isnullS[INDEX_MAX_KEYS];

/*
 * Write itup vector to page, has no control of free space
 */
OffsetNumber
gistfillbuffer(Relation r, Page page, IndexTuple *itup,
			   int len, OffsetNumber off)
{
	OffsetNumber l = InvalidOffsetNumber;
	int			i;

	if (off == InvalidOffsetNumber)
		off = (PageIsEmpty(page)) ? FirstOffsetNumber :
			OffsetNumberNext(PageGetMaxOffsetNumber(page));

	for (i = 0; i < len; i++)
	{
		l = PageAddItem(page, (Item) itup[i], IndexTupleSize(itup[i]),
						off, false, false);
		if (l == InvalidOffsetNumber)
			elog(ERROR, "failed to add item to index page in \"%s\"",
				 RelationGetRelationName(r));
		off++;
	}
	return l;
}

/*
 * Check space for itup vector on page
 */
bool
gistnospace(Page page, IndexTuple *itvec, int len, OffsetNumber todelete, Size freespace)
{
	unsigned int size = freespace,
				deleted = 0;
	int			i;

	for (i = 0; i < len; i++)
		size += IndexTupleSize(itvec[i]) + sizeof(ItemIdData);

	if (todelete != InvalidOffsetNumber)
	{
		IndexTuple	itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, todelete));

		deleted = IndexTupleSize(itup) + sizeof(ItemIdData);
	}

	return (PageGetFreeSpace(page) + deleted < size);
}

bool
gistfitpage(IndexTuple *itvec, int len)
{
	int			i;
	Size		size = 0;

	for (i = 0; i < len; i++)
		size += IndexTupleSize(itvec[i]) + sizeof(ItemIdData);

	/* TODO: Consider fillfactor */
	return (size <= GiSTPageSize);
}

/*
 * Read buffer into itup vector
 */
IndexTuple *
gistextractpage(Page page, int *len /* out */ )
{
	OffsetNumber i,
				maxoff;
	IndexTuple *itvec;

	maxoff = PageGetMaxOffsetNumber(page);
	*len = maxoff;
	itvec = palloc(sizeof(IndexTuple) * maxoff);
	for (i = FirstOffsetNumber; i <= maxoff; i = OffsetNumberNext(i))
		itvec[i - FirstOffsetNumber] = (IndexTuple) PageGetItem(page, PageGetItemId(page, i));

	return itvec;
}

/*
 * join two vectors into one
 */
IndexTuple *
gistjoinvector(IndexTuple *itvec, int *len, IndexTuple *additvec, int addlen)
{
	itvec = (IndexTuple *) repalloc((void *) itvec, sizeof(IndexTuple) * ((*len) + addlen));
	memmove(&itvec[*len], additvec, sizeof(IndexTuple) * addlen);
	*len += addlen;
	return itvec;
}

/*
 * make plain IndexTupleVector
 */

IndexTupleData *
gistfillitupvec(IndexTuple *vec, int veclen, int *memlen)
{
	char	   *ptr,
			   *ret;
	int			i;

	*memlen = 0;

	for (i = 0; i < veclen; i++)
		*memlen += IndexTupleSize(vec[i]);

	ptr = ret = palloc(*memlen);

	for (i = 0; i < veclen; i++)
	{
		memcpy(ptr, vec[i], IndexTupleSize(vec[i]));
		ptr += IndexTupleSize(vec[i]);
	}

	return (IndexTupleData *) ret;
}

/*
 * Make unions of keys in IndexTuple vector, return FALSE if itvec contains
 * invalid tuple. Resulting Datums aren't compressed.
 */

bool
gistMakeUnionItVec(GISTSTATE *giststate, IndexTuple *itvec, int len, int startkey,
				   Datum *attr, bool *isnull)
{
	int			i;
	GistEntryVector *evec;
	int			attrsize;

	evec = (GistEntryVector *) palloc((len + 2) * sizeof(GISTENTRY) + GEVHDRSZ);

	for (i = startkey; i < giststate->tupdesc->natts; i++)
	{
		int			j;

		evec->n = 0;
		if (!isnull[i])
		{
			gistentryinit(evec->vector[evec->n], attr[i],
						  NULL, NULL, (OffsetNumber) 0,
						  FALSE);
			evec->n++;
		}

		for (j = 0; j < len; j++)
		{
			Datum		datum;
			bool		IsNull;

			if (GistTupleIsInvalid(itvec[j]))
				return FALSE;	/* signals that union with invalid tuple =>
								 * result is invalid */

			datum = index_getattr(itvec[j], i + 1, giststate->tupdesc, &IsNull);
			if (IsNull)
				continue;

			gistdentryinit(giststate, i,
						   evec->vector + evec->n,
						   datum,
						   NULL, NULL, (OffsetNumber) 0,
						   FALSE, IsNull);
			evec->n++;
		}

		/* If this tuple vector was all NULLs, the union is NULL */
		if (evec->n == 0)
		{
			attr[i] = (Datum) 0;
			isnull[i] = TRUE;
		}
		else
		{
			if (evec->n == 1)
			{
				evec->n = 2;
				evec->vector[1] = evec->vector[0];
			}

			/* Make union and store in attr array */
			attr[i] = FunctionCall2(&giststate->unionFn[i],
									PointerGetDatum(evec),
									PointerGetDatum(&attrsize));

			isnull[i] = FALSE;
		}
	}

	return TRUE;
}

/*
 * Return an IndexTuple containing the result of applying the "union"
 * method to the specified IndexTuple vector.
 */
IndexTuple
gistunion(Relation r, IndexTuple *itvec, int len, GISTSTATE *giststate)
{
	memset(isnullS, TRUE, sizeof(bool) * giststate->tupdesc->natts);

	if (!gistMakeUnionItVec(giststate, itvec, len, 0, attrS, isnullS))
		return gist_form_invalid_tuple(InvalidBlockNumber);

	return gistFormTuple(giststate, r, attrS, isnullS, false);
}

/*
 * makes union of two key
 */
void
gistMakeUnionKey(GISTSTATE *giststate, int attno,
				 GISTENTRY *entry1, bool isnull1,
				 GISTENTRY *entry2, bool isnull2,
				 Datum *dst, bool *dstisnull)
{

	int			dstsize;

	static char storage[2 * sizeof(GISTENTRY) + GEVHDRSZ];
	GistEntryVector *evec = (GistEntryVector *) storage;

	evec->n = 2;

	if (isnull1 && isnull2)
	{
		*dstisnull = TRUE;
		*dst = (Datum) 0;
	}
	else
	{
		if (isnull1 == FALSE && isnull2 == FALSE)
		{
			evec->vector[0] = *entry1;
			evec->vector[1] = *entry2;
		}
		else if (isnull1 == FALSE)
		{
			evec->vector[0] = *entry1;
			evec->vector[1] = *entry1;
		}
		else
		{
			evec->vector[0] = *entry2;
			evec->vector[1] = *entry2;
		}

		*dstisnull = FALSE;
		*dst = FunctionCall2(&giststate->unionFn[attno],
							 PointerGetDatum(evec),
							 PointerGetDatum(&dstsize));
	}
}

bool
gistKeyIsEQ(GISTSTATE *giststate, int attno, Datum a, Datum b)
{
	bool		result;

	FunctionCall3(&giststate->equalFn[attno],
				  a, b,
				  PointerGetDatum(&result));
	return result;
}

/*
 * Decompress all keys in tuple
 */
void
gistDeCompressAtt(GISTSTATE *giststate, Relation r, IndexTuple tuple, Page p,
				  OffsetNumber o, GISTENTRY *attdata, bool *isnull)
{
	int			i;

	for (i = 0; i < r->rd_att->natts; i++)
	{
		Datum		datum = index_getattr(tuple, i + 1, giststate->tupdesc, &isnull[i]);

		gistdentryinit(giststate, i, &attdata[i],
					   datum, r, p, o,
					   FALSE, isnull[i]);
	}
}

/*
 * Forms union of oldtup and addtup, if union == oldtup then return NULL
 */
IndexTuple
gistgetadjusted(Relation r, IndexTuple oldtup, IndexTuple addtup, GISTSTATE *giststate)
{
	bool		neednew = FALSE;
	GISTENTRY	oldentries[INDEX_MAX_KEYS],
				addentries[INDEX_MAX_KEYS];
	bool		oldisnull[INDEX_MAX_KEYS],
				addisnull[INDEX_MAX_KEYS];
	IndexTuple	newtup = NULL;
	int			i;

	if (GistTupleIsInvalid(oldtup) || GistTupleIsInvalid(addtup))
		return gist_form_invalid_tuple(ItemPointerGetBlockNumber(&(oldtup->t_tid)));

	gistDeCompressAtt(giststate, r, oldtup, NULL,
					  (OffsetNumber) 0, oldentries, oldisnull);

	gistDeCompressAtt(giststate, r, addtup, NULL,
					  (OffsetNumber) 0, addentries, addisnull);

	for (i = 0; i < r->rd_att->natts; i++)
	{
		gistMakeUnionKey(giststate, i,