greenplumn gistsplit 源码
greenplumn gistsplit 代码
文件路径：/src/backend/access/gist/gistsplit.c
/*-------------------------------------------------------------------------
*
* gistsplit.c
* Multi-column page splitting algorithm
*
* This file is concerned with making good page-split decisions in multi-column
* GiST indexes. The opclass-specific picksplit functions can only be expected
* to produce answers based on a single column. We first run the picksplit
* function for column 1; then, if there are more columns, we check if any of
* the tuples are "don't cares" so far as the column 1 split is concerned
* (that is, they could go to either side for no additional penalty). If so,
* we try to redistribute those tuples on the basis of the next column.
* Repeat till we're out of columns.
*
* gistSplitByKey() is the entry point to this file.
*
*
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* src/backend/access/gist/gistsplit.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/gist_private.h"
#include "utils/rel.h"
typedef struct
{
OffsetNumber *entries;
int len;
Datum *attr;
bool *isnull;
bool *dontcare;
} GistSplitUnion;
/*
* Form unions of subkeys in itvec[] entries listed in gsvp->entries[],
* ignoring any tuples that are marked in gsvp->dontcare[]. Subroutine for
* gistunionsubkey.
*/
static void
gistunionsubkeyvec(GISTSTATE *giststate, IndexTuple *itvec,
GistSplitUnion *gsvp)
{
IndexTuple *cleanedItVec;
int i,
cleanedLen = 0;
cleanedItVec = (IndexTuple *) palloc(sizeof(IndexTuple) * gsvp->len);
for (i = 0; i < gsvp->len; i++)
{
if (gsvp->dontcare && gsvp->dontcare[gsvp->entries[i]])
continue;
cleanedItVec[cleanedLen++] = itvec[gsvp->entries[i] - 1];
}
gistMakeUnionItVec(giststate, cleanedItVec, cleanedLen,
gsvp->attr, gsvp->isnull);
pfree(cleanedItVec);
}
/*
* Recompute unions of left- and right-side subkeys after a page split,
* ignoring any tuples that are marked in spl->spl_dontcare[].
*
* Note: we always recompute union keys for all index columns. In some cases
* this might represent duplicate work for the leftmost column(s), but it's
* not safe to assume that "zero penalty to move a tuple" means "the union
* key doesn't change at all". Penalty functions aren't 100% accurate.
*/
static void
gistunionsubkey(GISTSTATE *giststate, IndexTuple *itvec, GistSplitVector *spl)
{
GistSplitUnion gsvp;
gsvp.dontcare = spl->spl_dontcare;
gsvp.entries = spl->splitVector.spl_left;
gsvp.len = spl->splitVector.spl_nleft;
gsvp.attr = spl->spl_lattr;
gsvp.isnull = spl->spl_lisnull;
gistunionsubkeyvec(giststate, itvec, &gsvp);
gsvp.entries = spl->splitVector.spl_right;
gsvp.len = spl->splitVector.spl_nright;
gsvp.attr = spl->spl_rattr;
gsvp.isnull = spl->spl_risnull;
gistunionsubkeyvec(giststate, itvec, &gsvp);
}
/*
* Find tuples that are "don't cares", that is could be moved to the other
* side of the split with zero penalty, so far as the attno column is
* concerned.
*
* Don't-care tuples are marked by setting the corresponding entry in
* spl->spl_dontcare[] to "true". Caller must have initialized that array
* to zeroes.
*
* Returns number of don't-cares found.
*/
static int
findDontCares(Relation r, GISTSTATE *giststate, GISTENTRY *valvec,
GistSplitVector *spl, int attno)
{
int i;
GISTENTRY entry;
int NumDontCare = 0;
/*
* First, search the left-side tuples to see if any have zero penalty to
* be added to the right-side union key.
*
* attno column is known all-not-null (see gistSplitByKey), so we need not
* check for nulls
*/
gistentryinit(entry, spl->splitVector.spl_rdatum, r, NULL,
(OffsetNumber) 0, false);
for (i = 0; i < spl->splitVector.spl_nleft; i++)
{
int j = spl->splitVector.spl_left[i];
float penalty = gistpenalty(giststate, attno, &entry, false,
&valvec[j], false);
if (penalty == 0.0)
{
spl->spl_dontcare[j] = true;
NumDontCare++;
}
}
/* And conversely for the right-side tuples */
gistentryinit(entry, spl->splitVector.spl_ldatum, r, NULL,
(OffsetNumber) 0, false);
for (i = 0; i < spl->splitVector.spl_nright; i++)
{
int j = spl->splitVector.spl_right[i];
float penalty = gistpenalty(giststate, attno, &entry, false,
&valvec[j], false);
if (penalty == 0.0)
{
spl->spl_dontcare[j] = true;
NumDontCare++;
}
}
return NumDontCare;
}
/*
* Remove tuples that are marked don't-cares from the tuple index array a[]
* of length *len. This is applied separately to the spl_left and spl_right
* arrays.
*/
static void
removeDontCares(OffsetNumber *a, int *len, const bool *dontcare)
{
int origlen,
newlen,
i;
OffsetNumber *curwpos;
origlen = newlen = *len;
curwpos = a;
for (i = 0; i < origlen; i++)
{
OffsetNumber ai = a[i];
if (dontcare[ai] == false)
{
/* re-emit item into a[] */
*curwpos = ai;
curwpos++;
}
else
newlen--;
}
*len = newlen;
}
/*
* Place a single don't-care tuple into either the left or right side of the
* split, according to which has least penalty for merging the tuple into
* the previously-computed union keys. We need consider only columns starting
* at attno.
*/
static void
placeOne(Relation r, GISTSTATE *giststate, GistSplitVector *v,
IndexTuple itup, OffsetNumber off, int attno)
{
GISTENTRY identry[INDEX_MAX_KEYS];
bool isnull[INDEX_MAX_KEYS];
bool toLeft = true;
gistDeCompressAtt(giststate, r, itup, NULL, (OffsetNumber) 0,
identry, isnull);
for (; attno < giststate->nonLeafTupdesc->natts; attno++)
{
float lpenalty,
rpenalty;
GISTENTRY entry;
gistentryinit(entry, v->spl_lattr[attno], r, NULL, 0, false);
lpenalty = gistpenalty(giststate, attno, &entry, v->spl_lisnull[attno],
identry + attno, isnull[attno]);
gistentryinit(entry, v->spl_rattr[attno], r, NULL, 0, false);
rpenalty = gistpenalty(giststate, attno, &entry, v->spl_risnull[attno],
identry + attno, isnull[attno]);
if (lpenalty != rpenalty)
{
if (lpenalty > rpenalty)
toLeft = false;
break;
}
}
if (toLeft)
v->splitVector.spl_left[v->splitVector.spl_nleft++] = off;
else
v->splitVector.spl_right[v->splitVector.spl_nright++] = off;
}
#define SWAPVAR( s, d, t ) \
do { \
(t) = (s); \
(s) = (d); \
(d) = (t); \
} while(0)
/*
* Clean up when we did a secondary split but the user-defined PickSplit
* method didn't support it (leaving spl_ldatum_exists or spl_rdatum_exists
* true).
*
* We consider whether to swap the left and right outputs of the secondary
* split; this can be worthwhile if the penalty for merging those tuples into
* the previously chosen sets is less that way.
*
* In any case we must update the union datums for the current column by
* adding in the previous union keys (oldL/oldR), since the user-defined
* PickSplit method didn't do so.
*/
static void
supportSecondarySplit(Relation r, GISTSTATE *giststate, int attno,
GIST_SPLITVEC *sv, Datum oldL, Datum oldR)
{
bool leaveOnLeft = true,
tmpBool;
GISTENTRY entryL,
entryR,
entrySL,
entrySR;
gistentryinit(entryL, oldL, r, NULL, 0, false);
gistentryinit(entryR, oldR, r, NULL, 0, false);
gistentryinit(entrySL, sv->spl_ldatum, r, NULL, 0, false);
gistentryinit(entrySR, sv->spl_rdatum, r, NULL, 0, false);
if (sv->spl_ldatum_exists && sv->spl_rdatum_exists)
{
float penalty1,
penalty2;
penalty1 = gistpenalty(giststate, attno, &entryL, false, &entrySL, false) +
gistpenalty(giststate, attno, &entryR, false, &entrySR, false);
penalty2 = gistpenalty(giststate, attno, &entryL, false, &entrySR, false) +
gistpenalty(giststate, attno, &entryR, false, &entrySL, false);
if (penalty1 > penalty2)
leaveOnLeft = false;
}
else
{
GISTENTRY *entry1 = (sv->spl_ldatum_exists) ? &entryL : &entryR;
float penalty1,
penalty2;
/*
* There is only one previously defined union, so we just choose swap
* or not by lowest penalty for that side. We can only get here if a
* secondary split happened to have all NULLs in its column in the
* tuples that the outer recursion level had assigned to one side.
* (Note that the null checks in gistSplitByKey don't prevent the
* case, because they'll only be checking tuples that were considered
* don't-cares at the outer recursion level, not the tuples that went
* into determining the passed-down left and right union keys.)
*/
penalty1 = gistpenalty(giststate, attno, entry1, false, &entrySL, false);
penalty2 = gistpenalty(giststate, attno, entry1, false, &entrySR, false);
if (penalty1 < penalty2)
leaveOnLeft = (sv->spl_ldatum_exists) ? true : false;
else
leaveOnLeft = (sv->spl_rdatum_exists) ? true : false;
}
if (leaveOnLeft == false)
{
/*
* swap left and right
*/
OffsetNumber *off,
noff;
Datum datum;
SWAPVAR(sv->spl_left, sv->spl_right, off);
SWAPVAR(sv->spl_nleft, sv->spl_nright, noff);
SWAPVAR(sv->spl_ldatum, sv->spl_rdatum, datum);
gistentryinit(entrySL, sv->spl_ldatum, r, NULL, 0, false);
gistentryinit(entrySR, sv->spl_rdatum, r, NULL, 0, false);
}
if (sv->spl_ldatum_exists)
gistMakeUnionKey(giststate, attno, &entryL, false, &entrySL, false,
&sv->spl_ldatum, &tmpBool);
if (sv->spl_rdatum_exists)
gistMakeUnionKey(giststate, attno, &entryR, false, &entrySR, false,
&sv->spl_rdatum, &tmpBool);
sv->spl_ldatum_exists = sv->spl_rdatum_exists = false;
}
/*
* Trivial picksplit implementation. Function called only
* if user-defined picksplit puts all keys on the same side of the split.
* That is a bug of user-defined picksplit but we don't want to fail.
*/
static void
genericPickSplit(GISTSTATE *giststate, GistEntryVector *entryvec, GIST_SPLITVEC *v, int attno)
{
OffsetNumber i,
maxoff;
int nbytes;
GistEntryVector *evec;
maxoff = entryvec->n - 1;
nbytes = (maxoff + 2) * sizeof(OffsetNumber);
v->spl_left = (OffsetNumber *) palloc(nbytes);
v->spl_right = (OffsetNumber *) palloc(nbytes);
v->spl_nleft = v->spl_nright = 0;
for (i = FirstOffsetNumber; i <= maxoff; i = OffsetNumberNext(i))
{
if (i <= (maxoff - FirstOffsetNumber + 1) / 2)
{
v->spl_left[v->spl_nleft] = i;
v->spl_nleft++;
}
else
{
v->spl_right[v->spl_nright] = i;
v->spl_nright++;
}
}
/*
* Form union datums for each side
*/
evec = palloc(sizeof(GISTENTRY) * entryvec->n + GEVHDRSZ);
evec->n = v->spl_nleft;
memcpy(evec->vector, entryvec->vector + FirstOffsetNumber,
sizeof(GISTENTRY) * evec->n);
v->spl_ldatum = FunctionCall2Coll(&giststate->unionFn[attno],
giststate->supportCollation[attno],
PointerGetDatum(evec),
PointerGetDatum(&nbytes));
evec->n = v->spl_nright;
memcpy(evec->vector, entryvec->vector + FirstOffsetNumber + v->spl_nleft,
sizeof(GISTENTRY) * evec->n);
v->spl_rdatum = FunctionCall2Coll(&giststate->unionFn[attno],
giststate->supportCollation[attno],
PointerGetDatum(evec),
PointerGetDatum(&nbytes));
}
/*
* Calls user picksplit method for attno column to split tuples into
* two vectors.
*
* Returns false if split is complete (there are no more index columns, or
* there is no need to consider them because split is optimal already).
*
* Returns true and v->spl_dontcare = NULL if the picksplit result is
* degenerate (all tuples seem to be don't-cares), so we should just
* disregard this column and split on the next column(s) instead.
*
* Returns true and v->spl_dontcare != NULL if there are don't-care tuples
* that could be relocated based on the next column(s). The don't-care
* tuples have been removed from the split and must be reinserted by caller.
* There is at least one non-don't-care tuple on each side of the split,
* and union keys for all columns are updated to include just those tuples.
*
* A true result implies there is at least one more index column.
*/
static bool
gistUserPicksplit(Relation r, GistEntryVector *entryvec, int attno, GistSplitVector *v,
IndexTuple *itup, int len pg_attribute_unused(), GISTSTATE *giststate)
{
GIST_SPLITVEC *sv = &v->splitVector;
/*
* Prepare spl_ldatum/spl_rdatum/spl_ldatum_exists/spl_rdatum_exists in
* case we are doing a secondary split (see comments in gist.h).
*/
sv->spl_ldatum_exists = (v->spl_lisnull[attno]) ? false : true;
sv->spl_rdatum_exists = (v->spl_risnull[attno]) ? false : true;
sv->spl_ldatum = v->spl_lattr[attno];
sv->spl_rdatum = v->spl_rattr[attno];
/*
* Let the opclass-specific PickSplit method do its thing. Note that at
* this point we know there are no null keys in the entryvec.
*/
FunctionCall2Coll(&giststate->picksplitFn[attno],
giststate->supportCollation[attno],
PointerGetDatum(entryvec),
PointerGetDatum(sv));
if (sv->spl_nleft == 0 || sv->spl_nright == 0)
{
/*
* User-defined picksplit failed to create an actual split, ie it put
* everything on the same side. Complain but cope.
*/
ereport(DEBUG1,
(errcode(ERRCODE_INTERNAL_ERROR),
errmsg("picksplit method for column %d of index \"%s\" failed",
attno + 1, RelationGetRelationName(r)),
errhint("The index is not optimal. To optimize it, contact a developer, or try to use the column as the second one in the CREATE INDEX command.")));
/*
* Reinit GIST_SPLITVEC. Although these fields are not used by
* genericPickSplit(), set them up for further processing
*/
sv->spl_ldatum_exists = (v->spl_lisnull[attno]) ? false : true;
sv->spl_rdatum_exists = (v->spl_risnull[attno]) ? false : true;
sv->spl_ldatum = v->spl_lattr[attno];
sv->spl_rdatum = v->spl_rattr[attno];
/* Do a generic split */
genericPickSplit(giststate, entryvec, sv, attno);
}
else
{
/* hack for compatibility with old picksplit API */
if (sv->spl_left[sv->spl_nleft - 1] == InvalidOffsetNumber)
sv->spl_left[sv->spl_nleft - 1] = (OffsetNumber) (entryvec->n - 1);
if (sv->spl_right[sv->spl_nright - 1] == InvalidOffsetNumber)
sv->spl_right[sv->spl_nright - 1] = (OffsetNumber) (entryvec->n - 1);
}
/* Clean up if PickSplit didn't take care of a secondary split */
if (sv->spl_ldatum_exists || sv->spl_rdatum_exists)
supportSecondarySplit(r, giststate, attno, sv,
v->spl_lattr[attno], v->spl_rattr[attno]);
/* emit union datums computed by PickSplit back to v arrays */
v->spl_lattr[attno] = sv->spl_ldatum;
v->spl_rattr[attno] = sv->spl_rdatum;
v->spl_lisnull[attno] = false;
v->spl_risnull[attno] = false;
/*
* If index columns remain, then consider whether we can improve the split
* by using them.
*/
v->spl_dontcare = NULL;
if (attno + 1 < giststate->nonLeafTupdesc->natts)
{
int NumDontCare;
/*
* Make a quick check to see if left and right union keys are equal;
* if so, the split is certainly degenerate, so tell caller to
* re-split with the next column.
*/
if (gistKeyIsEQ(giststate, attno, sv->spl_ldatum, sv->spl_rdatum))
return true;
/*
* Locate don't-care tuples, if any. If there are none, the split is
* optimal, so just fall out and return false.
*/
v->spl_dontcare = (bool *) palloc0(sizeof(bool) * (entryvec->n + 1));
NumDontCare = findDontCares(r, giststate, entryvec->vector, v, attno);
if (NumDontCare > 0)
{
/*
* Remove don't-cares from spl_left[] and spl_right[].
*/
removeDontCares(sv->spl_left, &sv->spl_nleft, v->spl_dontcare);
removeDontCares(sv->spl_right, &sv->spl_nright, v->spl_dontcare);
/*
* If all tuples on either side were don't-cares, the split is
* degenerate, and we're best off to ignore it and split on the
* next column. (We used to try to press on with a secondary
* split by forcing a random tuple on each side to be treated as
* non-don't-care, but it seems unlikely that that technique
* really gives a better result. Note that we don't want to try a
* secondary split with empty left or right primary split sides,
* because then there is no union key on that side for the
* PickSplit function to try to expand, so it can have no good
* figure of merit for what it's doing. Also note that this check
* ensures we can't produce a bogus one-side-only split in the
* NumDontCare == 1 special case below.)
*/
if (sv->spl_nleft == 0 || sv->spl_nright == 0)
{
v->spl_dontcare = NULL;
return true;
}
/*
* Recompute union keys, considering only non-don't-care tuples.
* NOTE: this will set union keys for remaining index columns,
* which will cause later calls of gistUserPicksplit to pass those
* values down to user-defined PickSplit methods with
* spl_ldatum_exists/spl_rdatum_exists set true.
*/
gistunionsubkey(giststate, itup, v);
if (NumDontCare == 1)
{
/*
* If there's only one don't-care tuple then we can't do a
* PickSplit on it, so just choose whether to send it left or
* right by comparing penalties. We needed the
* gistunionsubkey step anyway so that we have appropriate
* union keys for figuring the penalties.
*/
OffsetNumber toMove;
/* find it ... */
for (toMove = FirstOffsetNumber; toMove < entryvec->n; toMove++)
{
if (v->spl_dontcare[toMove])
break;
}
Assert(toMove < entryvec->n);
/* ... and assign it to cheaper side */
placeOne(r, giststate, v, itup[toMove - 1], toMove, attno + 1);
/*
* At this point the union keys are wrong, but we don't care
* because we're done splitting. The outermost recursion
* level of gistSplitByKey will fix things before returning.
*/
}
else
return true;
}
}
return false;
}
/*
* simply split page in half
*/
static void
gistSplitHalf(GIST_SPLITVEC *v, int len)
{
int i;
v->spl_nright = v->spl_nleft = 0;
v->spl_left = (OffsetNumber *) palloc(len * sizeof(OffsetNumber));
v->spl_right = (OffsetNumber *) palloc(len * sizeof(OffsetNumber));
for (i = 1; i <= len; i++)
if (i < len / 2)
v->spl_right[v->spl_nright++] = i;
else
v->spl_left[v->spl_nleft++] = i;
/* we need not compute union keys, caller took care of it */
}
/*
* gistSplitByKey: main entry point for page-splitting algorithm
*
* r: index relation
* page: page being split
* itup: array of IndexTuples to be processed
* len: number of IndexTuples to be processed (must be at least 2)
* giststate: additional info about index
* v: working state and output area
* attno: column we are working on (zero-based index)
*
* Outside caller must initialize v->spl_lisnull and v->spl_risnull arrays
* to all-true. On return, spl_left/spl_nleft contain indexes of tuples
* to go left, spl_right/spl_nright contain indexes of tuples to go right,
* spl_lattr/spl_lisnull contain left-side union key values, and
* spl_rattr/spl_risnull contain right-side union key values. Other fields
* in this struct are workspace for this file.
*
* Outside caller must pass zero for attno. The function may internally
* recurse to the next column by passing attno+1.
*/
void
gistSplitByKey(Relation r, Page page, IndexTuple *itup, int len,
GISTSTATE *giststate, GistSplitVector *v, int attno)
{
GistEntryVector *entryvec;
OffsetNumber *offNullTuples;
int nOffNullTuples = 0;
int i;
/* generate the item array, and identify tuples with null keys */
/* note that entryvec->vector[0] goes unused in this code */
entryvec = palloc(GEVHDRSZ + (len + 1) * sizeof(GISTENTRY));
entryvec->n = len + 1;
offNullTuples = (OffsetNumber *) palloc(len * sizeof(OffsetNumber));
for (i = 1; i <= len; i++)
{
Datum datum;
bool IsNull;
datum = index_getattr(itup[i - 1], attno + 1, giststate->leafTupdesc,
&IsNull);
gistdentryinit(giststate, attno, &(entryvec->vector[i]),
datum, r, page, i,
false, IsNull);
if (IsNull)
offNullTuples[nOffNullTuples++] = i;
}
if (nOffNullTuples == len)
{
/*
* Corner case: All keys in attno column are null, so just transfer
* our attention to the next column. If there's no next column, just
* split page in half.
*/
v->spl_risnull[attno] = v->spl_lisnull[attno] = true;
if (attno + 1 < giststate->nonLeafTupdesc->natts)
gistSplitByKey(r, page, itup, len, giststate, v, attno + 1);
else
gistSplitHalf(&v->splitVector, len);
}
else if (nOffNullTuples > 0)
{
int j = 0;
/*
* We don't want to mix NULL and not-NULL keys on one page, so split
* nulls to right page and not-nulls to left.
*/
v->splitVector.spl_right = offNullTuples;
v->splitVector.spl_nright = nOffNullTuples;
v->spl_risnull[attno] = true;
v->splitVector.spl_left = (OffsetNumber *) palloc(len * sizeof(OffsetNumber));
v->splitVector.spl_nleft = 0;
for (i = 1; i <= len; i++)
if (j < v->splitVector.spl_nright && offNullTuples[j] == i)
j++;
else
v->splitVector.spl_left[v->splitVector.spl_nleft++] = i;
/* Compute union keys, unless outer recursion level will handle it */
if (attno == 0 && giststate->nonLeafTupdesc->natts == 1)
{
v->spl_dontcare = NULL;
gistunionsubkey(giststate, itup, v);
}
}
else
{
/*
* All keys are not-null, so apply user-defined PickSplit method
*/
if (gistUserPicksplit(r, entryvec, attno, v, itup, len, giststate))
{
/*
* Splitting on attno column is not optimal, so consider
* redistributing don't-care tuples according to the next column
*/
Assert(attno + 1 < giststate->nonLeafTupdesc->natts);
if (v->spl_dontcare == NULL)
{
/*
* This split was actually degenerate, so ignore it altogether
* and just split according to the next column.
*/
gistSplitByKey(r, page, itup, len, giststate, v, attno + 1);
}
else
{
/*
* Form an array of just the don't-care tuples to pass to a
* recursive invocation of this function for the next column.
*/
IndexTuple *newitup = (IndexTuple *) palloc(len * sizeof(IndexTuple));
OffsetNumber *map = (OffsetNumber *) palloc(len * sizeof(OffsetNumber));
int newlen = 0;
GIST_SPLITVEC backupSplit;
for (i = 0; i < len; i++)
{
if (v->spl_dontcare[i + 1])
{
newitup[newlen] = itup[i];
map[newlen] = i + 1;
newlen++;
}
}
Assert(newlen > 0);
/*
* Make a backup copy of v->splitVector, since the recursive
* call will overwrite that with its own result.
*/
backupSplit = v->splitVector;
backupSplit.spl_left = (OffsetNumber *) palloc(sizeof(OffsetNumber) * len);
memcpy(backupSplit.spl_left, v->splitVector.spl_left, sizeof(OffsetNumber) * v->splitVector.spl_nleft);
backupSplit.spl_right = (OffsetNumber *) palloc(sizeof(OffsetNumber) * len);
memcpy(backupSplit.spl_right, v->splitVector.spl_right, sizeof(OffsetNumber) * v->splitVector.spl_nright);
/* Recursively decide how to split the don't-care tuples */
gistSplitByKey(r, page, newitup, newlen, giststate, v, attno + 1);
/* Merge result of subsplit with non-don't-care tuples */
for (i = 0; i < v->splitVector.spl_nleft; i++)
backupSplit.spl_left[backupSplit.spl_nleft++] = map[v->splitVector.spl_left[i] - 1];
for (i = 0; i < v->splitVector.spl_nright; i++)
backupSplit.spl_right[backupSplit.spl_nright++] = map[v->splitVector.spl_right[i] - 1];
v->splitVector = backupSplit;
}
}
}
/*
* If we're handling a multicolumn index, at the end of the recursion
* recompute the left and right union datums for all index columns. This
* makes sure we hand back correct union datums in all corner cases,
* including when we haven't processed all columns to start with, or when
* a secondary split moved "don't care" tuples from one side to the other
* (we really shouldn't assume that that didn't change the union datums).
*
* Note: when we're in an internal recursion (attno > 0), we do not worry
* about whether the union datums we return with are sensible, since
* calling levels won't care. Also, in a single-column index, we expect
* that PickSplit (or the special cases above) produced correct union
* datums.
*/
if (attno == 0 && giststate->nonLeafTupdesc->natts > 1)
{
v->spl_dontcare = NULL;
gistunionsubkey(giststate, itup, v);
}
}
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