/*-------------------------------------------------------------------------
*
* gistutil.c
* utilities routines for the postgres GiST index access method.
*
*
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/gist/gistutil.c,v 1.4 2005/06/28 15:51:00 teodor Exp $
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/genam.h"
#include "access/gist_private.h"
#include "access/gistscan.h"
#include "access/heapam.h"
#include "catalog/index.h"
#include "miscadmin.h"
#include "storage/freespace.h"
/* group flags ( in gistadjsubkey ) */
#define LEFT_ADDED 0x01
#define RIGHT_ADDED 0x02
#define BOTH_ADDED ( LEFT_ADDED | RIGHT_ADDED )
/*
* This defines is only for shorter code, used in gistgetadjusted
* and gistadjsubkey only
*/
#define FILLITEM(evp, isnullkey, okey, okeyb, rkey, rkeyb) do { \
if (isnullkey) { \
gistentryinit((evp), rkey, r, NULL, \
(OffsetNumber) 0, rkeyb, FALSE); \
} else { \
gistentryinit((evp), okey, r, NULL, \
(OffsetNumber) 0, okeyb, FALSE); \
} \
} while(0)
#define FILLEV(isnull1, key1, key1b, isnull2, key2, key2b) do { \
FILLITEM(*ev0p, isnull1, key1, key1b, key2, key2b); \
FILLITEM(*ev1p, isnull2, key2, key2b, key1, key1b); \
} while(0);
static void
gistpenalty(GISTSTATE *giststate, int attno,
GISTENTRY *key1, bool isNull1,
GISTENTRY *key2, bool isNull2, float *penalty);
/*
* 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, LP_USED);
if (l == InvalidOffsetNumber)
elog(ERROR, "gistfillbuffer: failed to add index item to \"%s\"",
RelationGetRelationName(r));
off++;
}
return l;
}
/*
* Check space for itup vector on page
*/
bool
gistnospace(Page page, IndexTuple *itvec, int len)
{
unsigned int size = 0;
int i;
for (i = 0; i < len; i++)
size += IndexTupleSize(itvec[i]) + sizeof(ItemIdData);
return (PageGetFreeSpace(page) < size);
}
/*
* Read buffer into itup vector
*/
IndexTuple *
gistextractbuffer(Buffer buffer, int *len /* out */ )
{
OffsetNumber i,
maxoff;
IndexTuple *itvec;
Page p = (Page) BufferGetPage(buffer);
maxoff = PageGetMaxOffsetNumber(p);
*len = maxoff;
itvec = palloc(sizeof(IndexTuple) * maxoff);
for (i = FirstOffsetNumber; i <= maxoff; i = OffsetNumberNext(i))
itvec[i - 1] = (IndexTuple) PageGetItem(p, PageGetItemId(p, 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;
}
/*
* 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)
{
Datum attr[INDEX_MAX_KEYS];
bool isnull[INDEX_MAX_KEYS];
GistEntryVector *evec;
int i;
GISTENTRY centry[INDEX_MAX_KEYS];
IndexTuple res;
evec = (GistEntryVector *) palloc(((len == 1) ? 2 : len) * sizeof(GISTENTRY) + GEVHDRSZ);
for(i = 0; i<len; i++)
if ( GistTupleIsInvalid( itvec[i] ) )
return gist_form_invalid_tuple( InvalidBlockNumber );
for (i = 0; i < r->rd_att->natts; i++)
{
Datum datum;
int j;
int real_len;
real_len = 0;
for (j = 0; j < len; j++)
{
bool IsNull;
datum = index_getattr(itvec[j], i + 1, giststate->tupdesc, &IsNull);
if (IsNull)
continue;
gistdentryinit(giststate, i,
&(evec->vector[real_len]),
datum,
NULL, NULL, (OffsetNumber) 0,
ATTSIZE(datum, giststate->tupdesc, i + 1, IsNull),
FALSE, IsNull);
real_len++;
}
/* If this tuple vector was all NULLs, the union is NULL */
if (real_len == 0)
{
attr[i] = (Datum) 0;
isnull[i] = TRUE;
}
else
{
int datumsize;
if (real_len == 1)
{
evec->n = 2;
gistentryinit(evec->vector[1],
evec->vector[0].key, r, NULL,
(OffsetNumber) 0, evec->vector[0].bytes, FALSE);
}
else
evec->n = real_len;
/* Compress the result of the union and store in attr array */
datum = FunctionCall2(&giststate->unionFn[i],
PointerGetDatum(evec),
PointerGetDatum(&datumsize));
gistcentryinit(giststate, i, ¢ry[i], datum,
NULL, NULL, (OffsetNumber) 0,
datumsize, FALSE, FALSE);
isnull[i] = FALSE;
attr[i] = centry[i].key;
}
}
res = index_form_tuple(giststate->tupdesc, attr, isnull);
GistTupleSetValid( res );
return res;
}
/*
* Forms union of oldtup and addtup, if union == oldtup then return NULL
*/
IndexTuple
gistgetadjusted(Relation r, IndexTuple oldtup, IndexTuple addtup, GISTSTATE *giststate)
{
GistEntryVector *evec;
bool neednew = false;
bool isnull[INDEX_MAX_KEYS];
Datum attr[INDEX_MAX_KEYS];
GISTENTRY centry[INDEX_MAX_KEYS],
oldatt[INDEX_MAX_KEYS],
addatt[INDEX_MAX_KEYS],
*ev0p,
*ev1p;
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) ) );
evec = palloc(2 * sizeof(GISTENTRY) + GEVHDRSZ);
evec->n = 2;
ev0p = &(evec->vector[0]);
ev1p = &(evec->vector[1]);
gistDeCompressAtt(giststate, r, oldtup, NULL,
(OffsetNumber) 0, oldatt, oldisnull);
gistDeCompressAtt(giststate, r, addtup, NULL,
(OffsetNumber) 0, addatt, addisnull);
for (i = 0; i < r->rd_att->natts; i++)
{
if (oldisnull[i] && addisnull[i])
{
attr[i] = (Datum) 0;
isnull[i] = TRUE;
}
else
{
Datum datum;
int datumsize;
FILLEV(oldisnull[i], oldatt[i].key, oldatt[i].bytes,
addisnull[i], addatt[i].key, addatt[i].bytes);
datum = FunctionCall2(&giststate->unionFn[i],
PointerGetDatum(evec),
PointerGetDatum(&datumsize));
if (oldisnull[i] || addisnull[i])
{
if (oldisnull[i])
neednew = true;
}
else
{
bool result;
FunctionCall3(&giststate->equalFn[i],
ev0p->key,
datum,
PointerGetDatum(&result));
if (!result)
neednew = true;
}
gistcentryinit(giststate, i, ¢ry[i], datum,
NULL, NULL, (OffsetNumber) 0,
datumsize, FALSE, FALSE);
attr[i] = centry[i].key;
isnull[i] = FALSE;
}
}
if (neednew)
{
/* need to update key */
newtup = index_form_tuple(giststate->tupdesc, attr, isnull);
newtup->t_tid = oldtup->t_tid;
}
return newtup;
}
void
gistunionsubkey(Relation r, GISTSTATE *giststate, IndexTuple *itvec, GIST_SPLITVEC *spl, bool isall)
{
int lr;
for (lr = 0; lr < 2; lr++)
{
OffsetNumber *entries;
int i;
Datum *attr;
int len,
*attrsize;
bool *isnull;
GistEntryVector *evec;
if (lr)
{
attrsize = spl->spl_lattrsize;
attr = spl->spl_lattr;
len = spl->spl_nleft;
entries = spl->spl_left;
isnull = spl->spl_lisnull;
}
else
{
attrsize = spl->spl_rattrsize;
attr = spl->spl_rattr;
len = spl->spl_nright;
entries = spl->spl_right;
isnull = spl->spl_risnull;
}
evec = palloc(((len < 2) ? 2 : len) * sizeof(GISTENTRY) + GEVHDRSZ);
for (i = (isall) ? 0 : 1; i < r->rd_att->natts; i++)
{
int j;
Datum datum;
int datumsize;
int real_len;
real_len = 0;
for (j = 0; j < len; j++)
{
bool IsNull;
if (spl->spl_idgrp[entries[j]])
continue;
datum = index_getattr(itvec[entries[j] - 1], i + 1,
giststate->tupdesc, &IsNull);
if (IsNull)
continue;
gistdentryinit(giststate, i,
&(evec->vector[real_len]),
datum,
NULL, NULL, (OffsetNumber) 0,
ATTSIZE(datum, giststate->tupdesc, i + 1, IsNull),
FALSE, IsNull);
real_len++;
}
if (real_len == 0)
{
datum = (Datum) 0;
datumsize = 0;
isnull[i] = true;
}
else
{
/*
* evec->vector[0].bytes may be not defined, so form union
* with itself
*/
if (real_len == 1)
{
evec->n = 2;
memcpy(&(evec->vector[1]), &(evec->vector[0]),
sizeof(GISTENTRY));
}
else
evec->n = real_len;
datum = FunctionCall2(&giststate->unionFn[i],
PointerGetDatum(evec),
PointerGetDatum(&datumsize));
isnull[i] = false;
}
attr[i] = datum;
attrsize[i] = datumsize;
}
}
}
/*
* find group in vector with equal value
*/
int
gistfindgroup(GISTSTATE *giststate, GISTENTRY *valvec, GIST_SPLITVEC *spl)
{
int i;
int curid = 1;
/*
* first key is always not null (see gistinsert), so we may not check
* for nulls
*/
for (i = 0; i < spl->spl_nleft; i++)
{
int j;
int len;
bool result;
if (spl->spl_idgrp[spl->spl_left[i]])
continue;
len = 0;
/* find all equal value in right part */
for (j = 0; j < spl->spl_nright; j++)
{
if (spl->spl_idgrp[spl->spl_right[j]])
continue;
FunctionCall3(&giststate->equalFn[0],
valvec[spl->spl_left[i]].key,
valvec[spl->spl_right[j]].key,
PointerGetDatum(&result));
if (result)
{
spl->spl_idgrp[spl->spl_right[j]] = curid;
len++;
}
}
/* find all other equal value in left part */
if (len)
{
/* add current val to list of equal values */
spl->spl_idgrp[spl->spl_left[i]] = curid;
/* searching .. */
for (j = i + 1; j < spl->spl_nleft; j++)
{
if (spl->spl_idgrp[spl->spl_left[j]])
continue;
FunctionCall3(&giststate->equalFn[0],
valvec[spl->spl_left[i]].key,
valvec[spl->spl_left[j]].key,
PointerGetDatum(&result));
if (result)
{
spl->spl_idgrp[spl->spl_left[j]] = curid;
len++;
}
}
spl->spl_ngrp[curid] = len + 1;
curid++;
}
}
return curid;
}
/*
* Insert equivalent tuples to left or right page with minimum
* penalty
*/
void
gistadjsubkey(Relation r,
IndexTuple *itup, /* contains compressed entry */
int len,
GIST_SPLITVEC *v,
GISTSTATE *giststate)
{
int curlen;
OffsetNumber *curwpos;
GISTENTRY entry,
identry[INDEX_MAX_KEYS],
*ev0p,
*ev1p;
float lpenalty,
rpenalty;
GistEntryVector *evec;
int datumsize;
bool isnull[INDEX_MAX_KEYS];
int i,
j;
/* clear vectors */
curlen = v->spl_nleft;
curwpos = v->spl_left;
for (i = 0; i < v->spl_nleft; i++)
{
if (v->spl_idgrp[v->spl_left[i]] == 0)
{
*curwpos = v->spl_left[i];
curwpos++;
}
else
curlen--;
}
v->spl_nleft = curlen;
curlen = v->spl_nright;
curwpos = v->spl_right;
for (i = 0; i < v->spl_nright; i++)
{
if (v->spl_idgrp[v->spl_right[i]] == 0)
{
*curwpos = v->spl_right[i];
curwpos++;
}
else
curlen--;
}
v->spl_nright = curlen;
evec = palloc(2 * sizeof(GISTENTRY) + GEVHDRSZ);
evec->n = 2;
ev0p = &(evec->vector[0]);
ev1p = &(evec->vector[1]);
/* add equivalent tuple */
for (i = 0; i < len; i++)
{
Datum datum;
if (v->spl_idgrp[i + 1] == 0) /* already inserted */
continue;
gistDeCompressAtt(giststate, r, itup[i], NULL, (OffsetNumber) 0,
identry, isnull);
v->spl_ngrp[v->spl_idgrp[i + 1]]--;
if (v->spl_ngrp[v->spl_idgrp[i + 1]] == 0 &&
(v->spl_grpflag[v->spl_idgrp[i + 1]] & BOTH_ADDED) != BOTH_ADDED)
{
/* force last in group */
rpenalty = 1.0;
lpenalty = (v->spl_grpflag[v->spl_idgrp[i + 1]] & LEFT_ADDED) ? 2.0 : 0.0;
}
else
{
/* where? */
for (j = 1; j < r->rd_att->natts; j++)
{
gistentryinit(entry, v->spl_lattr[j], r, NULL,
(OffsetNumber) 0, v->spl_lattrsize[j], FALSE);
gistpenalty(giststate, j, &entry, v->spl_lisnull[j],
&identry[j], isnull[j], &lpenalty);
gistentryinit(entry, v->spl_rattr[j], r, NULL,
(OffsetNumber) 0, v->spl_rattrsize[j], FALSE);
gistpenalty(giststate, j, &entry, v->spl_risnull[j],
&identry[j], isnull[j], &rpenalty);
if (lpenalty != rpenalty)
break;
}
}
/*
* add
* XXX: refactor this to avoid duplicating code
*/
if (lpenalty < rpenalty)
{
v->spl_grpflag[v->spl_idgrp[i + 1]] |= LEFT_ADDED;
v->spl_left[v->spl_nleft] = i + 1;
v->spl_nleft++;
for (j = 1; j < r->rd_att->natts; j++)
{
if (isnull[j] && v->spl_lisnull[j])
{
v->spl_lattr[j] = (Datum) 0;
v->spl_lattrsize[j] = 0;
}
else
{
FILLEV(v->spl_lisnull[j], v->spl_lattr[j], v->spl_lattrsize[j],
isnull[j], identry[j].key, identry[j].bytes);
datum = FunctionCall2(&giststate->unionFn[j],
PointerGetDatum(evec),
PointerGetDatum(&datumsize));
v->spl_lattr[j] = datum;
v->spl_lattrsize[j] = datumsize;
v->spl_lisnull[j] = false;
}
}
}
else
{
v->spl_grpflag[v->spl_idgrp[i + 1]] |= RIGHT_ADDED;
v->spl_right[v->spl_nright] = i + 1;
v->spl_nright++;
for (j = 1; j < r->rd_att->natts; j++)
{
if (isnull[j] && v->spl_risnull[j])
{
v->spl_rattr[j] = (Datum) 0;
v->spl_rattrsize[j] = 0;
}
else
{
FILLEV(v->spl_risnull[j], v->spl_rattr[j], v->spl_rattrsize[j],
isnull[j], identry[j].key, identry[j].bytes);
datum = FunctionCall2(&giststate->unionFn[j],
PointerGetDatum(evec),
PointerGetDatum(&datumsize));
v->spl_rattr[j] = datum;
v->spl_rattrsize[j] = datumsize;
v->spl_risnull[j] = false;
}
}
}
}
}
/*
* find entry with lowest penalty
*/
OffsetNumber
gistchoose(Relation r, Page p, IndexTuple it, /* it has compressed entry */
GISTSTATE *giststate)
{
OffsetNumber maxoff;
OffsetNumber i;
OffsetNumber which;
float sum_grow,
which_grow[INDEX_MAX_KEYS];
GISTENTRY entry,
identry[INDEX_MAX_KEYS];
bool isnull[INDEX_MAX_KEYS];
maxoff = PageGetMaxOffsetNumber(p);
*which_grow = -1.0;
which = InvalidOffsetNumber;
sum_grow = 1;
gistDeCompressAtt(giststate, r,
it, NULL, (OffsetNumber) 0,
identry, isnull);
for (i = FirstOffsetNumber; i <= maxoff && sum_grow; i = OffsetNumberNext(i))
{
int j;
IndexTuple itup = (IndexTuple) PageGetItem(p, PageGetItemId(p, i));
if ( !GistPageIsLeaf(p) && GistTupleIsInvalid(itup) ) {
elog(LOG, "It's desirable to vacuum or reindex GiST index '%s' due to crash recovery",
RelationGetRelationName(r));
continue;
}
sum_grow = 0;
for (j = 0; j < r->rd_att->natts; j++)
{
Datum datum;
float usize;
bool IsNull;
datum = index_getattr(itup, j + 1, giststate->tupdesc, &IsNull);
gistdentryinit(giststate, j, &entry, datum, r, p, i,
ATTSIZE(datum, giststate->tupdesc, j + 1, IsNull),
FALSE, IsNull);
gistpenalty(giststate, j, &entry, IsNull,
&identry[j], isnull[j], &usize);
if (which_grow[j] < 0 || usize < which_grow[j])
{
which = i;
which_grow[j] = usize;
if (j < r->rd_att->natts - 1 && i == FirstOffsetNumber)
which_grow[j + 1] = -1;
sum_grow += which_grow[j];
}
else if (which_grow[j] == usize)
sum_grow += usize;
else
{
sum_grow = 1;
break;
}
}
}
if ( which == InvalidOffsetNumber )
which = FirstOffsetNumber;
return which;
}
/*
* initialize a GiST entry with a decompressed version of key
*/
void
gistdentryinit(GISTSTATE *giststate, int nkey, GISTENTRY *e,
Datum k, Relation r, Page pg, OffsetNumber o,
int b, bool l, bool isNull)
{
if (b && !isNull)
{
GISTENTRY *dep;
gistentryinit(*e, k, r, pg, o, b, l);
dep = (GISTENTRY *)
DatumGetPointer(FunctionCall1(&giststate->decompressFn[nkey],
PointerGetDatum(e)));
/* decompressFn may just return the given pointer */
if (dep != e)
gistentryinit(*e, dep->key, dep->rel, dep->page, dep->offset,
dep->bytes, dep->leafkey);
}
else
gistentryinit(*e, (Datum) 0, r, pg, o, 0, l);
}
/*
* initialize a GiST entry with a compressed version of key
*/
void
gistcentryinit(GISTSTATE *giststate, int nkey,
GISTENTRY *e, Datum k, Relation r,
Page pg, OffsetNumber o, int b, bool l, bool isNull)
{
if (!isNull)
{
GISTENTRY *cep;
gistentryinit(*e, k, r, pg, o, b, l);
cep = (GISTENTRY *)
DatumGetPointer(FunctionCall1(&giststate->compressFn[nkey],
PointerGetDatum(e)));
/* compressFn may just return the given pointer */
if (cep != e)
gistentryinit(*e, cep->key, cep->rel, cep->page, cep->offset,
cep->bytes, cep->leafkey);
}
else
gistentryinit(*e, (Datum) 0, r, pg, o, 0, l);
}
IndexTuple
gistFormTuple(GISTSTATE *giststate, Relation r,
Datum attdata[], int datumsize[], bool isnull[])
{
GISTENTRY centry[INDEX_MAX_KEYS];
Datum compatt[INDEX_MAX_KEYS];
int i;
IndexTuple res;
for (i = 0; i < r->rd_att->natts; i++)
{
if (isnull[i])
compatt[i] = (Datum) 0;
else
{
gistcentryinit(giststate, i, ¢ry[i], attdata[i],
NULL, NULL, (OffsetNumber) 0,
datumsize[i], FALSE, FALSE);
compatt[i] = centry[i].key;
}
}
res = index_form_tuple(giststate->tupdesc, compatt, isnull);
GistTupleSetValid(res);
return res;
}
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,
ATTSIZE(datum, giststate->tupdesc, i + 1, isnull[i]),
FALSE, isnull[i]);
}
}
static void
gistpenalty(GISTSTATE *giststate, int attno,
GISTENTRY *key1, bool isNull1,
GISTENTRY *key2, bool isNull2, float *penalty)
{
if (giststate->penaltyFn[attno].fn_strict && (isNull1 || isNull2))
*penalty = 0.0;
else
FunctionCall3(&giststate->penaltyFn[attno],
PointerGetDatum(key1),
PointerGetDatum(key2),
PointerGetDatum(penalty));
}
void
GISTInitBuffer(Buffer b, uint32 f)
{
GISTPageOpaque opaque;
Page page;
Size pageSize;
pageSize = BufferGetPageSize(b);
page = BufferGetPage(b);
PageInit(page, pageSize, sizeof(GISTPageOpaqueData));
opaque = GistPageGetOpaque(page);
opaque->flags = f;
opaque->nsplited = 0;
opaque->level = 0;
opaque->rightlink = InvalidBlockNumber;
memset( &(opaque->nsn), 0, sizeof(GistNSN) );
}
void
gistUserPicksplit(Relation r, GistEntryVector *entryvec, GIST_SPLITVEC *v,
IndexTuple *itup, int len, GISTSTATE *giststate) {
/*
* now let the user-defined picksplit function set up the split
* vector; in entryvec have no null value!!
*/
FunctionCall2(&giststate->picksplitFn[0],
PointerGetDatum(entryvec),
PointerGetDatum(v));
/* compatibility with old code */
if (v->spl_left[v->spl_nleft - 1] == InvalidOffsetNumber)
v->spl_left[v->spl_nleft - 1] = (OffsetNumber) (entryvec->n - 1);
if (v->spl_right[v->spl_nright - 1] == InvalidOffsetNumber)
v->spl_right[v->spl_nright - 1] = (OffsetNumber) (entryvec->n - 1);
v->spl_lattr[0] = v->spl_ldatum;
v->spl_rattr[0] = v->spl_rdatum;
v->spl_lisnull[0] = false;
v->spl_risnull[0] = false;
/*
* if index is multikey, then we must to try get smaller bounding box
* for subkey(s)
*/
if (r->rd_att->natts > 1)
{
int MaxGrpId;
v->spl_idgrp = (int *) palloc0(sizeof(int) * entryvec->n);
v->spl_grpflag = (char *) palloc0(sizeof(char) * entryvec->n);
v->spl_ngrp = (int *) palloc(sizeof(int) * entryvec->n);
MaxGrpId = gistfindgroup(giststate, entryvec->vector, v);
/* form union of sub keys for each page (l,p) */
gistunionsubkey(r, giststate, itup, v, false);
/*
* if possible, we insert equivalent tuples with control by
* penalty for a subkey(s)
*/
if (MaxGrpId > 1)
gistadjsubkey(r, itup, len, v, giststate);
}
}
Buffer
gistNewBuffer(Relation r) {
Buffer buffer = InvalidBuffer;
bool needLock;
while(true) {
BlockNumber blkno = GetFreeIndexPage(&r->rd_node);
if (blkno == InvalidBlockNumber)
break;
buffer = ReadBuffer(r, blkno);
if ( ConditionalLockBuffer(buffer) ) {
Page page = BufferGetPage(buffer);
if ( GistPageIsDeleted( page ) ) {
GistPageSetNonDeleted( page );
return buffer;
} else
LockBuffer(buffer, GIST_UNLOCK);
}
ReleaseBuffer( buffer );
}
needLock = !RELATION_IS_LOCAL(r);
if (needLock)
LockRelationForExtension(r, ExclusiveLock);
buffer = ReadBuffer(r, P_NEW);
LockBuffer(buffer, GIST_EXCLUSIVE);
if (needLock)
UnlockRelationForExtension(r, ExclusiveLock);
return buffer;
}