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I have made three changes to the rtree code: one bug fix and

Browse Source 
two performance improvements.  I put an explanation of the
changes at

http://cs1.cs.nyu.edu/been/postgres-rtree.html

The performance improvements are quite significant.

All the changes are in the file src/backend/access/rtree/rtree.c

I was working with the 7.1.3 code.

I'm including the diff output as an attachment.

Kenneth Been
This commit is contained in:
Bruce Momjian 2001-09-29 03:46:12 +00:00
parent 7d94ac3b23
commit 818fb55ac4
1 changed files with 214 additions and 67 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

281
src/backend/access/rtree/rtree.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/access/rtree/Attic/rtree.c,v 1.63 2001/07/15 22:48:16 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/access/rtree/Attic/rtree.c,v 1.64 2001/09/29 03:46:12 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@ -55,6 +55,14 @@ typedef struct SPLITVEC
Datum spl_rdatum;
} SPLITVEC;
/* for sorting tuples by cost, for picking split */
typedef struct SPLITCOST
{
OffsetNumber offset_number;
float cost_differential;
bool choose_left;
} SPLITCOST;
typedef struct RTSTATE
{
FmgrInfo unionFn; /* union function */
@ -92,6 +100,7 @@ static OffsetNumber choose(Relation r, Page p, IndexTuple it,
RTSTATE *rtstate);
static int nospace(Page p, IndexTuple it);
static void initRtstate(RTSTATE *rtstate, Relation index);
static int qsort_comp_splitcost(const void *a, const void *b);
/*
@ -366,7 +375,12 @@ rttighten(Relation r,
FunctionCall2(&rtstate->sizeFn, datum,
PointerGetDatum(&newd_size));
if (newd_size != old_size)
/*
* If newd_size == 0 we have degenerate rectangles, so we
* don't know if there was any change, so we have to
* assume there was.
*/
if ((newd_size == 0) || (newd_size != old_size))
{
TupleDesc td = RelationGetDescr(r);
@ -442,6 +456,8 @@ rtdosplit(Relation r,
OffsetNumber *spl_left,
*spl_right;
TupleDesc tupDesc;
int n;
OffsetNumber newitemoff;
p = (Page) BufferGetPage(buffer);
opaque = (RTreePageOpaque) PageGetSpecialPointer(p);
@ -478,56 +494,64 @@ rtdosplit(Relation r,
spl_right = v.spl_right;
leftoff = rightoff = FirstOffsetNumber;
maxoff = PageGetMaxOffsetNumber(p);
for (i = FirstOffsetNumber; i <= maxoff; i = OffsetNumberNext(i))
{
itemid = PageGetItemId(p, i);
item = (IndexTuple) PageGetItem(p, itemid);
if (i == *spl_left)
{
if (PageAddItem(left, (Item) item, IndexTupleSize(item),
leftoff, LP_USED) == InvalidOffsetNumber)
elog(ERROR, "rtdosplit: failed to copy index item in %s",
RelationGetRelationName(r));
leftoff = OffsetNumberNext(leftoff);
spl_left++; /* advance in left split vector */
}
else
{
Assert(i == *spl_right);
if (PageAddItem(right, (Item) item, IndexTupleSize(item),
rightoff, LP_USED) == InvalidOffsetNumber)
elog(ERROR, "rtdosplit: failed to copy index item in %s",
RelationGetRelationName(r));
rightoff = OffsetNumberNext(rightoff);
spl_right++; /* advance in right split vector */
}
}
newitemoff = OffsetNumberNext(maxoff);
/* build an InsertIndexResult for this insertion */
res = (InsertIndexResult) palloc(sizeof(InsertIndexResultData));
/* now insert the new index tuple */
if (*spl_left == maxoff + 1)
/*
* spl_left contains a list of the offset numbers of the
* tuples that will go to the left page. For each offset
* number, get the tuple item, then add the item to the
* left page. Similarly for the right side.
*/
/* fill left node */
for (n = 0; n < v.spl_nleft; n++)
{
if (PageAddItem(left, (Item) itup, IndexTupleSize(itup),
i = *spl_left;
if (i == newitemoff)
item = itup;
else
{
itemid = PageGetItemId(p, i);
item = (IndexTuple) PageGetItem(p, itemid);
}
if (PageAddItem(left, (Item) item, IndexTupleSize(item),
leftoff, LP_USED) == InvalidOffsetNumber)
elog(ERROR, "rtdosplit: failed to add index item to %s",
RelationGetRelationName(r));
leftoff = OffsetNumberNext(leftoff);
ItemPointerSet(&(res->pointerData), lbknum, leftoff);
spl_left++;
if (i == newitemoff)
ItemPointerSet(&(res->pointerData), lbknum, leftoff);
spl_left++; /* advance in left split vector */
}
else
/* fill right node */
for (n = 0; n < v.spl_nright; n++)
{
Assert(*spl_right == maxoff + 1);
if (PageAddItem(right, (Item) itup, IndexTupleSize(itup),
i = *spl_right;
if (i == newitemoff)
item = itup;
else
{
itemid = PageGetItemId(p, i);
item = (IndexTuple) PageGetItem(p, itemid);
}
if (PageAddItem(right, (Item) item, IndexTupleSize(item),
rightoff, LP_USED) == InvalidOffsetNumber)
elog(ERROR, "rtdosplit: failed to add index item to %s",
RelationGetRelationName(r));
rightoff = OffsetNumberNext(rightoff);
ItemPointerSet(&(res->pointerData), rbknum, rightoff);
spl_right++;
if (i == newitemoff)
ItemPointerSet(&(res->pointerData), rbknum, rightoff);
spl_right++; /* advance in right split vector */
}
/* Make sure we consumed all of the split vectors, and release 'em */
@ -680,8 +704,10 @@ rtnewroot(Relation r, IndexTuple lt, IndexTuple rt)
* In addition, the item to be added (itup) is listed in the appropriate
* vector. It is represented by item number N+1 (N = # of items on page).
*
* Both vectors appear in sequence order with a terminating sentinel value
* of InvalidOffsetNumber.
* Both vectors have a terminating sentinel value of InvalidOffsetNumber,
* but the sentinal value is no longer used, because the SPLITVEC
* vector also contains the length of each vector, and that information
* is now used to iterate over them in rtdosplit(). --kbb, 21 Sept 2001
*
* The bounding-box datums for the two new pages are also returned in *v.
*
@ -736,6 +762,12 @@ rtpicksplit(Relation r,
item_2_sz,
left_avail_space,
right_avail_space;
int total_num_tuples,
num_tuples_without_seeds,
max_after_split; /* in Guttman's lingo, (M - m) */
float diff; /* diff between cost of putting tuple left or right */
SPLITCOST *cost_vector;
int n;
/*
* First, make sure the new item is not so large that we can't
@ -751,6 +783,9 @@ rtpicksplit(Relation r,
maxoff = PageGetMaxOffsetNumber(page);
newitemoff = OffsetNumberNext(maxoff); /* phony index for new
* item */
total_num_tuples = newitemoff;
num_tuples_without_seeds = total_num_tuples - 2;
max_after_split = total_num_tuples / 2; /* works for m = M/2 */
/* Make arrays big enough for worst case, including sentinel */
nbytes = (maxoff + 2) * sizeof(OffsetNumber);
@ -848,47 +883,111 @@ rtpicksplit(Relation r,
right_avail_space = RTPageAvailSpace - IndexTupleTotalSize(item_2);
/*
* Now split up the regions between the two seeds. An important
* property of this split algorithm is that the split vector v has the
* indices of items to be split in order in its left and right
* vectors. We exploit this property by doing a merge in the code
* that actually splits the page.
* Now split up the regions between the two seeds.
*
* For efficiency, we also place the new index tuple in this loop. This
* is handled at the very end, when we have placed all the existing
* tuples and i == maxoff + 1.
* The cost_vector array will contain hints for determining where
* each tuple should go. Each record in the array will contain
* a boolean, choose_left, that indicates which node the tuple
* prefers to be on, and the absolute difference in cost between
* putting the tuple in its favored node and in the other node.
*
* Later, we will sort the cost_vector in descending order by cost
* difference, and consider the tuples in that order for
* placement. That way, the tuples that *really* want to be in
* one node or the other get to choose first, and the tuples that
* don't really care choose last.
*
* First, build the cost_vector array. The new index tuple will
* also be handled in this loop, and represented in the array,
* with i==newitemoff.
*
* In the case of variable size tuples it is possible that we only
* have the two seeds and no other tuples, in which case we don't
* do any of this cost_vector stuff.
*/
/* to keep compiler quiet */
cost_vector = (SPLITCOST *) NULL;
if (num_tuples_without_seeds > 0)
{
cost_vector =
(SPLITCOST *) palloc(num_tuples_without_seeds * sizeof(SPLITCOST));
n = 0;
for (i = FirstOffsetNumber; i <= newitemoff; i = OffsetNumberNext(i))
{
/* Compute new union datums and sizes for both choices */
if ((i == seed_1) || (i == seed_2))
continue;
else if (i == newitemoff)
item_1 = itup;
else
item_1 = (IndexTuple) PageGetItem(page, PageGetItemId(page, i));
datum_alpha = IndexTupleGetDatum(item_1);
union_dl = FunctionCall2(&rtstate->unionFn, datum_l, datum_alpha);
union_dr = FunctionCall2(&rtstate->unionFn, datum_r, datum_alpha);
FunctionCall2(&rtstate->sizeFn, union_dl,
PointerGetDatum(&size_alpha));
FunctionCall2(&rtstate->sizeFn, union_dr,
PointerGetDatum(&size_beta));
diff = (size_alpha - size_l) - (size_beta - size_r);
cost_vector[n].offset_number = i;
cost_vector[n].cost_differential = fabs(diff);
cost_vector[n].choose_left = (diff < 0);
n++;
}
/*
* Sort the array. The function qsort_comp_splitcost is
* set up "backwards", to provided descending order.
*/
qsort(cost_vector, num_tuples_without_seeds, sizeof(SPLITCOST),
&qsort_comp_splitcost);
}
/*
* Now make the final decisions about where each tuple will go,
* and build the vectors to return in the SPLITVEC record.
*
* The cost_vector array contains (descriptions of) all the
* tuples, in the order that we want to consider them, so we
* we just iterate through it and place each tuple in left
* or right nodes, according to the criteria described below.
*/
left = v->spl_left;
v->spl_nleft = 0;
right = v->spl_right;
v->spl_nright = 0;
for (i = FirstOffsetNumber; i <= newitemoff; i = OffsetNumberNext(i))
/* Place the seeds first.
* left avail space, left union, right avail space, and right
* union have already been adjusted for the seeds.
*/
*left++ = seed_1;
v->spl_nleft++;
*right++ = seed_2;
v->spl_nright++;
for (n = 0; n < num_tuples_without_seeds; n++)
{
bool left_feasible,
right_feasible,
choose_left;
/*
* If we've already decided where to place this item, just put it
* on the correct list. Otherwise, we need to figure out which
* page needs the least enlargement in order to store the item.
* We need to figure out which page needs the least
* enlargement in order to store the item.
*/
if (i == seed_1)
{
*left++ = i;
v->spl_nleft++;
/* left avail_space & union already includes this one */
continue;
}
if (i == seed_2)
{
*right++ = i;
v->spl_nright++;
/* right avail_space & union already includes this one */
continue;
}
i = cost_vector[n].offset_number;
/* Compute new union datums and sizes for both possible additions */
if (i == newitemoff)
@ -918,6 +1017,24 @@ rtpicksplit(Relation r,
* (We know that all the old items together can fit on one page, so
* we need not worry about any other problem than failing to fit
* the new item.)
*
* Guttman's algorithm actually has two factors to consider (in
* order): 1. if one node has so many tuples already assigned to
* it that the other needs all the rest in order to satisfy the
* condition that neither node has fewer than m tuples, then
* that is decisive; 2. otherwise, choose the page that shows
* the smaller enlargement of its union area.
*
* I have chosen m = M/2, where M is the maximum number of
* tuples on a page. (Actually, this is only strictly
* true for fixed size tuples. For variable size tuples,
* there still might have to be only one tuple on a page,
* if it is really big. But even with variable size
* tuples we still try to get m as close as possible to M/2.)
*
* The question of which page shows the smaller enlargement of
* its union area has already been answered, and the answer
* stored in the choose_left field of the SPLITCOST record.
*/
left_feasible = (left_avail_space >= item_1_sz &&
((left_avail_space - item_1_sz) >= newitemsz ||
@ -927,8 +1044,18 @@ rtpicksplit(Relation r,
left_avail_space >= newitemsz));
if (left_feasible && right_feasible)
{
/* Both feasible, use Guttman's algorithm */
choose_left = (size_alpha - size_l < size_beta - size_r);
/*
* Both feasible, use Guttman's algorithm.
* First check the m condition described above, and if
* that doesn't apply, choose the page with the smaller
* enlargement of its union area.
*/
if (v->spl_nleft > max_after_split)
choose_left = false;
else if (v->spl_nright > max_after_split)
choose_left = true;
else
choose_left = cost_vector[n].choose_left;
}
else if (left_feasible)
choose_left = true;
@ -962,6 +1089,11 @@ rtpicksplit(Relation r,
}
}
if (num_tuples_without_seeds > 0)
{
pfree(cost_vector);
}
*left = *right = InvalidOffsetNumber; /* add ending sentinels */
v->spl_ldatum = datum_l;
@ -1145,6 +1277,21 @@ initRtstate(RTSTATE *rtstate, Relation index)
return;
}
/* for sorting SPLITCOST records in descending order */
static int
qsort_comp_splitcost(const void *a, const void *b)
{
float diff =
((SPLITCOST *)a)->cost_differential -
((SPLITCOST *)b)->cost_differential;
if (diff < 0)
return 1;
else if (diff > 0)
return -1;
else
return 0;
}
#ifdef RTDEBUG
void