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Improved cost estimation for IVFFlat [skip ci]

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This commit is contained in:
Andrew Kane
2024-09-28 15:43:28 -07:00
parent 158d9340bc
commit 0f36e15bea
2 changed files with 13 additions and 14 deletions
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25
src/ivfflat.c
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@@ -85,6 +85,8 @@ ivfflatcostestimate(PlannerInfo *root, IndexPath *path, double loop_count,
MemSet(&costs, 0, sizeof(costs)); MemSet(&costs, 0, sizeof(costs));
genericcostestimate(root, path, loop_count, &costs);
index = index_open(path->indexinfo->indexoid, NoLock); index = index_open(path->indexinfo->indexoid, NoLock);
IvfflatGetMetaPageInfo(index, &lists, NULL); IvfflatGetMetaPageInfo(index, &lists, NULL);
index_close(index, NoLock); index_close(index, NoLock);
@@ -94,14 +96,9 @@ ivfflatcostestimate(PlannerInfo *root, IndexPath *path, double loop_count,
if (ratio > 1.0) if (ratio > 1.0)
ratio = 1.0; ratio = 1.0;
/* /* Set startup cost since most work happens before first tuple is returned */
* This gives us the subset of tuples to visit. This value is passed into costs.indexStartupCost = costs.indexTotalCost * ratio;
* the generic cost estimator to determine the number of pages to visit costs.numIndexPages *= ratio;
* during the index scan.
*/
costs.numIndexTuples = path->indexinfo->tuples * ratio;
genericcostestimate(root, path, loop_count, &costs);
get_tablespace_page_costs(path->indexinfo->reltablespace, NULL, &spc_seq_page_cost); get_tablespace_page_costs(path->indexinfo->reltablespace, NULL, &spc_seq_page_cost);
@@ -109,23 +106,25 @@ ivfflatcostestimate(PlannerInfo *root, IndexPath *path, double loop_count,
if (costs.numIndexPages > path->indexinfo->rel->pages && ratio < 0.5) if (costs.numIndexPages > path->indexinfo->rel->pages && ratio < 0.5)
{ {
/* Change all page cost from random to sequential */ /* Change all page cost from random to sequential */
costs.indexTotalCost -= costs.numIndexPages * (costs.spc_random_page_cost - spc_seq_page_cost); costs.indexStartupCost -= costs.numIndexPages * (costs.spc_random_page_cost - spc_seq_page_cost);
/* Remove cost of extra pages */ /* Remove cost of extra pages */
costs.indexTotalCost -= (costs.numIndexPages - path->indexinfo->rel->pages) * spc_seq_page_cost; costs.indexStartupCost -= (costs.numIndexPages - path->indexinfo->rel->pages) * spc_seq_page_cost;
} }
else else
{ {
/* Change some page cost from random to sequential */ /* Change some page cost from random to sequential */
costs.indexTotalCost -= 0.5 * costs.numIndexPages * (costs.spc_random_page_cost - spc_seq_page_cost); costs.indexStartupCost -= 0.5 * costs.numIndexPages * (costs.spc_random_page_cost - spc_seq_page_cost);
} }
/* Use total cost since most work happens before first tuple is returned */ *indexStartupCost = costs.indexStartupCost;
*indexStartupCost = costs.indexTotalCost;
*indexTotalCost = costs.indexTotalCost; *indexTotalCost = costs.indexTotalCost;
*indexSelectivity = costs.indexSelectivity; *indexSelectivity = costs.indexSelectivity;
*indexCorrelation = costs.indexCorrelation; *indexCorrelation = costs.indexCorrelation;
*indexPages = costs.numIndexPages; *indexPages = costs.numIndexPages;
Assert(*indexStartupCost > 0);
Assert(*indexTotalCost > 0);
} }
/* /*

2
test/t/040_ivfflat_cost.pl
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@@ -21,7 +21,7 @@ for my $dim (@dims)
# Create table and index # Create table and index
$node->safe_psql("postgres", "CREATE TABLE tst (i int4, v vector($dim));"); $node->safe_psql("postgres", "CREATE TABLE tst (i int4, v vector($dim));");
$node->safe_psql("postgres", $node->safe_psql("postgres",
"INSERT INTO tst SELECT i, ARRAY[$array_sql] FROM generate_series(1, 5000) i;" "INSERT INTO tst SELECT i, ARRAY[$array_sql] FROM generate_series(1, 6000) i;"
); );
$node->safe_psql("postgres", "CREATE INDEX idx ON tst USING ivfflat (v vector_l2_ops) WITH (lists = 5);"); $node->safe_psql("postgres", "CREATE INDEX idx ON tst USING ivfflat (v vector_l2_ops) WITH (lists = 5);");
$node->safe_psql("postgres", "ANALYZE tst;"); $node->safe_psql("postgres", "ANALYZE tst;");