diff options
Diffstat (limited to 'src/backend/optimizer/path/costsize.c')
| -rw-r--r-- | src/backend/optimizer/path/costsize.c | 67 |
1 files changed, 62 insertions, 5 deletions
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c index 1d5e66337ce..e45e454a375 100644 --- a/src/backend/optimizer/path/costsize.c +++ b/src/backend/optimizer/path/costsize.c @@ -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; @@ -644,6 +666,34 @@ cost_tidscan(Path *path, PlannerInfo *root, } /* + * 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)) { |