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synced 2025-11-15 03:41:20 +03:00
First cut at making indexscan cost estimates depend on correlation
between index order and table order.
This commit is contained in:
Tom Lane
@@ -15,7 +15,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.88 2001/05/07 00:43:23 tgl Exp $
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* $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.89 2001/05/09 23:13:35 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@@ -39,6 +39,7 @@
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#include "optimizer/cost.h"
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#include "parser/parse_func.h"
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#include "parser/parse_oper.h"
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#include "parser/parsetree.h"
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#include "utils/builtins.h"
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#include "utils/date.h"
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#include "utils/int8.h"
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@@ -818,7 +819,6 @@ eqjoinsel(PG_FUNCTION_ARGS)
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{
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#ifdef NOT_USED /* see neqjoinsel() before removing me! */
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Oid opid = PG_GETARG_OID(0);
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#endif
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Oid relid1 = PG_GETARG_OID(1);
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AttrNumber attno1 = PG_GETARG_INT16(2);
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@@ -2230,16 +2230,14 @@ string_to_datum(const char *str, Oid datatype)
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*-------------------------------------------------------------------------
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*/
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static Datum
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genericcostestimate(PG_FUNCTION_ARGS)
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static void
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genericcostestimate(Query *root, RelOptInfo *rel,
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IndexOptInfo *index, List *indexQuals,
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Cost *indexStartupCost,
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Cost *indexTotalCost,
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Selectivity *indexSelectivity,
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double *indexCorrelation)
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{
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Query *root = (Query *) PG_GETARG_POINTER(0);
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RelOptInfo *rel = (RelOptInfo *) PG_GETARG_POINTER(1);
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IndexOptInfo *index = (IndexOptInfo *) PG_GETARG_POINTER(2);
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List *indexQuals = (List *) PG_GETARG_POINTER(3);
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Cost *indexStartupCost = (Cost *) PG_GETARG_POINTER(4);
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Cost *indexTotalCost = (Cost *) PG_GETARG_POINTER(5);
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Selectivity *indexSelectivity = (Selectivity *) PG_GETARG_POINTER(6);
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double numIndexTuples;
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double numIndexPages;
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@@ -2275,33 +2273,134 @@ genericcostestimate(PG_FUNCTION_ARGS)
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*indexTotalCost = numIndexPages +
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(cpu_index_tuple_cost + cost_qual_eval(indexQuals)) * numIndexTuples;
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PG_RETURN_VOID();
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/*
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* Generic assumption about index correlation: there isn't any.
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*/
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*indexCorrelation = 0.0;
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}
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/*
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* For first cut, just use generic function for all index types.
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*/
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Datum
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btcostestimate(PG_FUNCTION_ARGS)
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{
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return genericcostestimate(fcinfo);
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Query *root = (Query *) PG_GETARG_POINTER(0);
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RelOptInfo *rel = (RelOptInfo *) PG_GETARG_POINTER(1);
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IndexOptInfo *index = (IndexOptInfo *) PG_GETARG_POINTER(2);
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List *indexQuals = (List *) PG_GETARG_POINTER(3);
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Cost *indexStartupCost = (Cost *) PG_GETARG_POINTER(4);
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Cost *indexTotalCost = (Cost *) PG_GETARG_POINTER(5);
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Selectivity *indexSelectivity = (Selectivity *) PG_GETARG_POINTER(6);
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double *indexCorrelation = (double *) PG_GETARG_POINTER(7);
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genericcostestimate(root, rel, index, indexQuals,
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indexStartupCost, indexTotalCost,
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indexSelectivity, indexCorrelation);
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/*
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* If it's a functional index, leave the default zero-correlation
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* estimate in place. If not, and if we can get an estimate for
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* the first variable's ordering correlation C from pg_statistic,
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* estimate the index correlation as C / number-of-columns.
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* (The idea here is that multiple columns dilute the importance
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* of the first column's ordering, but don't negate it entirely.)
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*/
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if (index->indproc == InvalidOid)
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{
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Oid relid;
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HeapTuple tuple;
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relid = getrelid(lfirsti(rel->relids), root->rtable);
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Assert(relid != InvalidOid);
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tuple = SearchSysCache(STATRELATT,
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ObjectIdGetDatum(relid),
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Int16GetDatum(index->indexkeys[0]),
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0, 0);
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if (HeapTupleIsValid(tuple))
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{
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Oid typid;
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int32 typmod;
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float4 *numbers;
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int nnumbers;
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get_atttypetypmod(relid, index->indexkeys[0],
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&typid, &typmod);
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if (get_attstatsslot(tuple, typid, typmod,
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STATISTIC_KIND_CORRELATION,
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index->ordering[0],
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NULL, NULL, &numbers, &nnumbers))
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{
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double varCorrelation;
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int nKeys;
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Assert(nnumbers == 1);
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varCorrelation = numbers[0];
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for (nKeys = 1; index->indexkeys[nKeys] != 0; nKeys++)
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/*skip*/;
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*indexCorrelation = varCorrelation / nKeys;
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free_attstatsslot(typid, NULL, 0, numbers, nnumbers);
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}
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ReleaseSysCache(tuple);
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}
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}
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PG_RETURN_VOID();
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}
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Datum
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rtcostestimate(PG_FUNCTION_ARGS)
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{
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return genericcostestimate(fcinfo);
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Query *root = (Query *) PG_GETARG_POINTER(0);
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RelOptInfo *rel = (RelOptInfo *) PG_GETARG_POINTER(1);
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IndexOptInfo *index = (IndexOptInfo *) PG_GETARG_POINTER(2);
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List *indexQuals = (List *) PG_GETARG_POINTER(3);
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Cost *indexStartupCost = (Cost *) PG_GETARG_POINTER(4);
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Cost *indexTotalCost = (Cost *) PG_GETARG_POINTER(5);
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Selectivity *indexSelectivity = (Selectivity *) PG_GETARG_POINTER(6);
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double *indexCorrelation = (double *) PG_GETARG_POINTER(7);
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genericcostestimate(root, rel, index, indexQuals,
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indexStartupCost, indexTotalCost,
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indexSelectivity, indexCorrelation);
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PG_RETURN_VOID();
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}
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Datum
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hashcostestimate(PG_FUNCTION_ARGS)
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{
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return genericcostestimate(fcinfo);
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Query *root = (Query *) PG_GETARG_POINTER(0);
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RelOptInfo *rel = (RelOptInfo *) PG_GETARG_POINTER(1);
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IndexOptInfo *index = (IndexOptInfo *) PG_GETARG_POINTER(2);
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List *indexQuals = (List *) PG_GETARG_POINTER(3);
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Cost *indexStartupCost = (Cost *) PG_GETARG_POINTER(4);
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Cost *indexTotalCost = (Cost *) PG_GETARG_POINTER(5);
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Selectivity *indexSelectivity = (Selectivity *) PG_GETARG_POINTER(6);
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double *indexCorrelation = (double *) PG_GETARG_POINTER(7);
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genericcostestimate(root, rel, index, indexQuals,
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indexStartupCost, indexTotalCost,
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indexSelectivity, indexCorrelation);
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PG_RETURN_VOID();
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}
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Datum
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gistcostestimate(PG_FUNCTION_ARGS)
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{
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return genericcostestimate(fcinfo);
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Query *root = (Query *) PG_GETARG_POINTER(0);
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RelOptInfo *rel = (RelOptInfo *) PG_GETARG_POINTER(1);
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IndexOptInfo *index = (IndexOptInfo *) PG_GETARG_POINTER(2);
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List *indexQuals = (List *) PG_GETARG_POINTER(3);
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Cost *indexStartupCost = (Cost *) PG_GETARG_POINTER(4);
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Cost *indexTotalCost = (Cost *) PG_GETARG_POINTER(5);
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Selectivity *indexSelectivity = (Selectivity *) PG_GETARG_POINTER(6);
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double *indexCorrelation = (double *) PG_GETARG_POINTER(7);
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genericcostestimate(root, rel, index, indexQuals,
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indexStartupCost, indexTotalCost,
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indexSelectivity, indexCorrelation);
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PG_RETURN_VOID();
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}
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32
src/backend/utils/cache/lsyscache.c
vendored
32
src/backend/utils/cache/lsyscache.c
vendored
@@ -7,7 +7,7 @@
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/utils/cache/lsyscache.c,v 1.54 2001/05/09 00:35:09 tgl Exp $
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* $Header: /cvsroot/pgsql/src/backend/utils/cache/lsyscache.c,v 1.55 2001/05/09 23:13:35 tgl Exp $
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*
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* NOTES
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* Eventually, the index information should go through here, too.
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@@ -185,6 +185,36 @@ get_atttypmod(Oid relid, AttrNumber attnum)
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return -1;
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}
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/*
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* get_atttypetypmod
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*
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* A two-fer: given the relation id and the attribute number,
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* fetch both type OID and atttypmod in a single cache lookup.
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*
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* Unlike the otherwise-similar get_atttype/get_atttypmod, this routine
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* raises an error if it can't obtain the information.
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*/
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void
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get_atttypetypmod(Oid relid, AttrNumber attnum,
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Oid *typid, int32 *typmod)
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{
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HeapTuple tp;
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Form_pg_attribute att_tup;
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tp = SearchSysCache(ATTNUM,
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ObjectIdGetDatum(relid),
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Int16GetDatum(attnum),
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0, 0);
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if (!HeapTupleIsValid(tp))
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elog(ERROR, "cache lookup failed for relation %u attribute %d",
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relid, attnum);
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att_tup = (Form_pg_attribute) GETSTRUCT(tp);
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*typid = att_tup->atttypid;
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*typmod = att_tup->atttypmod;
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ReleaseSysCache(tp);
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}
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/* ---------- INDEX CACHE ---------- */
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/* watch this space...
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