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Added basic cost estimation [skip ci]

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This commit is contained in:
Andrew Kane
2023-08-05 11:55:24 -07:00
parent 405b7d98dc
commit 11e0b87abe
1 changed files with 17 additions and 3 deletions
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20
src/hnsw.c
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@@ -1,6 +1,7 @@
#include "postgres.h"
#include <float.h>
#include <math.h>
#include "access/amapi.h"
#include "commands/vacuum.h"
@@ -69,6 +70,9 @@ hnswcostestimate(PlannerInfo *root, IndexPath *path, double loop_count,
double *indexPages)
{
GenericCosts costs;
int m;
int entryLevel;
Relation index;
#if PG_VERSION_NUM < 120000
List *qinfos;
#endif
@@ -86,6 +90,17 @@ hnswcostestimate(PlannerInfo *root, IndexPath *path, double loop_count,
MemSet(&costs, 0, sizeof(costs));
index = index_open(path->indexinfo->indexoid, NoLock);
m = HnswGetM(index);
index_close(index, NoLock);
/* Approximate entry level */
entryLevel = (int) -log(1.0 / path->indexinfo->tuples) * HnswGetMl(m);
/* TODO Improve estimate of visited tuples (currently underestimates) */
/* Account for number of tuples (or entry level), m, and ef_search */
costs.numIndexTuples = (entryLevel + 2) * m;
#if PG_VERSION_NUM >= 120000
genericcostestimate(root, path, loop_count, &costs);
#else
@@ -93,9 +108,8 @@ hnswcostestimate(PlannerInfo *root, IndexPath *path, double loop_count,
genericcostestimate(root, path, loop_count, qinfos, &costs);
#endif
/* TODO Improve cost estimate */
*indexStartupCost = costs.indexStartupCost;
/* Use total cost since most work happens before first tuple is returned */
*indexStartupCost = costs.indexTotalCost;
*indexTotalCost = costs.indexTotalCost;
*indexSelectivity = costs.indexSelectivity;
*indexCorrelation = costs.indexCorrelation;