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Commit0aed62f

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Better solution to the IN-list issue: instead of having an arbitrary cutoff,
treat Var and non-Var IN-list items differently. Only non-Var items arecandidates to go into an ANY(ARRAY) construct --- we put all Vars as separateOR conditions on the grounds that that leaves more scope for optimization.Per suggestion from Robert Haas.
1 parentaa0fb53 commit0aed62f

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‎src/backend/parser/parse_expr.c

Lines changed: 30 additions & 34 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/parser/parse_expr.c,v 1.236 2008/10/25 17:19:09 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/parser/parse_expr.c,v 1.237 2008/10/26 02:46:25 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -939,11 +939,13 @@ transformAExprOf(ParseState *pstate, A_Expr *a)
939939
staticNode*
940940
transformAExprIn(ParseState*pstate,A_Expr*a)
941941
{
942+
Node*result=NULL;
942943
Node*lexpr;
943944
List*rexprs;
945+
List*rvars;
946+
List*rnonvars;
944947
booluseOr;
945948
boolhaveRowExpr;
946-
Node*result;
947949
ListCell*l;
948950

949951
/*
@@ -959,41 +961,33 @@ transformAExprIn(ParseState *pstate, A_Expr *a)
959961
* possible if the inputs are all scalars (no RowExprs) and there is a
960962
* suitable array type available. If not, we fall back to a boolean
961963
* condition tree with multiple copies of the lefthand expression.
964+
* Also, any IN-list items that contain Vars are handled as separate
965+
* boolean conditions, because that gives the planner more scope for
966+
* optimization on such clauses.
962967
*
963968
* First step: transform all the inputs, and detect whether any are
964-
* RowExprs.
969+
* RowExprs or contain Vars.
965970
*/
966971
lexpr=transformExpr(pstate,a->lexpr);
967972
haveRowExpr= (lexpr&&IsA(lexpr,RowExpr));
968-
rexprs=NIL;
973+
rexprs=rvars=rnonvars=NIL;
969974
foreach(l, (List*)a->rexpr)
970975
{
971976
Node*rexpr=transformExpr(pstate,lfirst(l));
972977

973978
haveRowExpr |= (rexpr&&IsA(rexpr,RowExpr));
974979
rexprs=lappend(rexprs,rexpr);
980+
if (contain_vars_of_level(rexpr,0))
981+
rvars=lappend(rvars,rexpr);
982+
else
983+
rnonvars=lappend(rnonvars,rexpr);
975984
}
976985

977986
/*
978-
* We prefer a boolean tree to ScalarArrayOpExpr if any of these are true:
979-
*
980-
* 1. We have a RowExpr anywhere.
981-
*
982-
* 2. There's only one righthand expression --- best to just generate a
983-
* simple = comparison.
984-
*
985-
* 3. There's a reasonably small number of righthand expressions and
986-
* they contain any Vars. This is a heuristic to support cases like
987-
* WHERE '555-1212' IN (tab.home_phone, tab.work_phone), which can be
988-
* optimized into an OR of indexscans on different indexes so long as
989-
* it's left as an OR tree. (It'd be better to leave this decision
990-
* to the planner, no doubt, but the amount of code required to reformat
991-
* the expression later on seems out of proportion to the benefit.)
987+
* ScalarArrayOpExpr is only going to be useful if there's more than
988+
* one non-Var righthand item. Also, it won't work for RowExprs.
992989
*/
993-
if (!(haveRowExpr||
994-
list_length(rexprs)==1||
995-
(list_length(rexprs) <=32&&
996-
contain_vars_of_level((Node*)rexprs,0))))
990+
if (!haveRowExpr&&list_length(rnonvars)>1)
997991
{
998992
List*allexprs;
999993
Oidscalar_type;
@@ -1004,9 +998,9 @@ transformAExprIn(ParseState *pstate, A_Expr *a)
1004998
* since the LHS' type is first in the list, it will be preferred when
1005999
* there is doubt (eg, when all the RHS items are unknown literals).
10061000
*
1007-
* Note: use list_concat here not lcons, to avoid damagingrexprs.
1001+
* Note: use list_concat here not lcons, to avoid damagingrnonvars.
10081002
*/
1009-
allexprs=list_concat(list_make1(lexpr),rexprs);
1003+
allexprs=list_concat(list_make1(lexpr),rnonvars);
10101004
scalar_type=select_common_type(pstate,allexprs,NULL,NULL);
10111005

10121006
/* Do we have an array type to use? */
@@ -1017,14 +1011,14 @@ transformAExprIn(ParseState *pstate, A_Expr *a)
10171011
if (array_type!=InvalidOid)
10181012
{
10191013
/*
1020-
* OK: coerce all the right-hand inputs to the common type and
1021-
* build an ArrayExpr for them.
1014+
* OK: coerce all the right-handnon-Varinputs to the common type
1015+
*andbuild an ArrayExpr for them.
10221016
*/
10231017
List*aexprs;
10241018
ArrayExpr*newa;
10251019

10261020
aexprs=NIL;
1027-
foreach(l,rexprs)
1021+
foreach(l,rnonvars)
10281022
{
10291023
Node*rexpr= (Node*)lfirst(l);
10301024

@@ -1040,19 +1034,21 @@ transformAExprIn(ParseState *pstate, A_Expr *a)
10401034
newa->multidims= false;
10411035
newa->location=-1;
10421036

1043-
return (Node*)make_scalar_array_op(pstate,
1044-
a->name,
1045-
useOr,
1046-
lexpr,
1047-
(Node*)newa,
1048-
a->location);
1037+
result= (Node*)make_scalar_array_op(pstate,
1038+
a->name,
1039+
useOr,
1040+
lexpr,
1041+
(Node*)newa,
1042+
a->location);
1043+
1044+
/* Consider only the Vars (if any) in the loop below */
1045+
rexprs=rvars;
10491046
}
10501047
}
10511048

10521049
/*
10531050
* Must do it the hard way, ie, with a boolean expression tree.
10541051
*/
1055-
result=NULL;
10561052
foreach(l,rexprs)
10571053
{
10581054
Node*rexpr= (Node*)lfirst(l);

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