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Teach tid-scan code to make use of "ctid = ANY (array)" clauses, so that

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"ctid IN (list)" will still work after we convert IN to ScalarArrayOpExpr.
Make some minor efficiency improvements while at it, such as ensuring that
multiple TIDs are fetched in physical heap order.  And fix EXPLAIN so that
it shows what's really going on for a TID scan.
This commit is contained in:
Tom Lane
2005-11-26 22:14:57 +00:00
parent a66e2c8885
commit da27c0a1ef
15 changed files with 378 additions and 147 deletions
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67
src/backend/optimizer/path/costsize.c
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@@ -49,7 +49,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.150 2005/11/22 18:17:12 momjian Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.151 2005/11/26 22:14:56 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -66,6 +66,7 @@
#include "optimizer/pathnode.h"
#include "optimizer/plancat.h"
#include "parser/parsetree.h"
#include "utils/array.h"
#include "utils/selfuncs.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"
@@ -104,6 +105,7 @@ bool enable_hashjoin = true;
static bool cost_qual_eval_walker(Node *node, QualCost *total);
static int estimate_array_length(Node *arrayexpr);
static Selectivity approx_selectivity(PlannerInfo *root, List *quals,
JoinType jointype);
static Selectivity join_in_selectivity(JoinPath *path, PlannerInfo *root);
@@ -617,12 +619,13 @@ cost_bitmap_or_node(BitmapOrPath *path, PlannerInfo *root)
*/
void
cost_tidscan(Path *path, PlannerInfo *root,
RelOptInfo *baserel, List *tideval)
RelOptInfo *baserel, List *tidquals)
{
Cost startup_cost = 0;
Cost run_cost = 0;
Cost cpu_per_tuple;
int ntuples = list_length(tideval);
int ntuples;
ListCell *l;
/* Should only be applied to base relations */
Assert(baserel->relid > 0);
@@ -631,6 +634,25 @@ cost_tidscan(Path *path, PlannerInfo *root,
if (!enable_tidscan)
startup_cost += disable_cost;
/* Count how many tuples we expect to retrieve */
ntuples = 0;
foreach(l, tidquals)
{
if (IsA(lfirst(l), ScalarArrayOpExpr))
{
/* Each element of the array yields 1 tuple */
ScalarArrayOpExpr *saop = (ScalarArrayOpExpr *) lfirst(l);
Node *arraynode = (Node *) lsecond(saop->args);
ntuples += estimate_array_length(arraynode);
}
else
{
/* It's just CTID = something, count 1 tuple */
ntuples++;
}
}
/* disk costs --- assume each tuple on a different page */
run_cost += random_page_cost * ntuples;
@@ -643,6 +665,34 @@ cost_tidscan(Path *path, PlannerInfo *root,
path->total_cost = startup_cost + run_cost;
}
/*
* Estimate number of elements in the array yielded by an expression.
*/
static int
estimate_array_length(Node *arrayexpr)
{
if (arrayexpr && IsA(arrayexpr, Const))
{
Datum arraydatum = ((Const *) arrayexpr)->constvalue;
bool arrayisnull = ((Const *) arrayexpr)->constisnull;
ArrayType *arrayval;
if (arrayisnull)
return 0;
arrayval = DatumGetArrayTypeP(arraydatum);
return ArrayGetNItems(ARR_NDIM(arrayval), ARR_DIMS(arrayval));
}
else if (arrayexpr && IsA(arrayexpr, ArrayExpr))
{
return list_length(((ArrayExpr *) arrayexpr)->elements);
}
else
{
/* default guess */
return 10;
}
}
/*
* cost_subqueryscan
* Determines and returns the cost of scanning a subquery RTE.
@@ -1549,8 +1599,15 @@ cost_qual_eval_walker(Node *node, QualCost *total)
total->per_tuple += cpu_operator_cost;
else if (IsA(node, ScalarArrayOpExpr))
{
/* should charge more than 1 op cost, but how many? */
total->per_tuple += cpu_operator_cost * 10;
/*
* Estimate that the operator will be applied to about half of the
* array elements before the answer is determined.
*/
ScalarArrayOpExpr *saop = (ScalarArrayOpExpr *) node;
Node *arraynode = (Node *) lsecond(saop->args);
total->per_tuple +=
cpu_operator_cost * estimate_array_length(arraynode) * 0.5;
}
else if (IsA(node, SubLink))
{