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COALESCE() and NULLIF() are now first-class expressions, not macros

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that turn into CASE expressions.  They evaluate their arguments at most
once.  Patch by Kris Jurka, review and (very light) editorializing by me.
This commit is contained in:
Tom Lane
2003-02-16 02:30:39 +00:00
parent de25638d2f
commit 51972a9d5d
22 changed files with 644 additions and 107 deletions
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5
src/backend/optimizer/path/costsize.c
View File

@@ -49,7 +49,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.106 2003/02/15 21:39:58 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.107 2003/02/16 02:30:38 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -1468,7 +1468,8 @@ cost_qual_eval_walker(Node *node, QualCost *total)
*/
if (IsA(node, FuncExpr) ||
IsA(node, OpExpr) ||
IsA(node, DistinctExpr))
IsA(node, DistinctExpr) ||
IsA(node, NullIfExpr))
{
total->per_tuple += cpu_operator_cost;
}

6
src/backend/optimizer/plan/setrefs.c
View File

@@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/setrefs.c,v 1.91 2003/01/20 18:54:52 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/setrefs.c,v 1.92 2003/02/16 02:30:38 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -284,6 +284,8 @@ fix_expr_references_walker(Node *node, void *context)
set_opfuncid((OpExpr *) node);
else if (IsA(node, DistinctExpr))
set_opfuncid((OpExpr *) node); /* rely on struct equivalence */
else if (IsA(node, NullIfExpr))
set_opfuncid((OpExpr *) node); /* rely on struct equivalence */
else if (IsA(node, SubPlan))
{
SubPlan *sp = (SubPlan *) node;
@@ -736,5 +738,7 @@ fix_opfuncids_walker(Node *node, void *context)
set_opfuncid((OpExpr *) node);
else if (IsA(node, DistinctExpr))
set_opfuncid((OpExpr *) node); /* rely on struct equivalence */
else if (IsA(node, NullIfExpr))
set_opfuncid((OpExpr *) node); /* rely on struct equivalence */
return expression_tree_walker(node, fix_opfuncids_walker, context);
}

97
src/backend/optimizer/util/clauses.c
View File

@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/util/clauses.c,v 1.129 2003/02/09 06:56:27 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/util/clauses.c,v 1.130 2003/02/16 02:30:38 tgl Exp $
*
* HISTORY
* AUTHOR DATE MAJOR EVENT
@@ -451,24 +451,22 @@ expression_returns_set_walker(Node *node, void *context)
return true;
/* else fall through to check args */
}
if (IsA(node, DistinctExpr))
{
DistinctExpr *expr = (DistinctExpr *) node;
if (expr->opretset)
return true;
/* else fall through to check args */
}
/* Avoid recursion for some cases that can't return a set */
if (IsA(node, BoolExpr))
return false;
if (IsA(node, Aggref))
return false;
if (IsA(node, DistinctExpr))
return false;
if (IsA(node, BoolExpr))
return false;
if (IsA(node, SubLink))
return false;
if (IsA(node, SubPlan))
return false;
if (IsA(node, CoalesceExpr))
return false;
if (IsA(node, NullIfExpr))
return false;
return expression_tree_walker(node, expression_returns_set_walker,
context);
@@ -559,6 +557,14 @@ contain_mutable_functions_walker(Node *node, void *context)
return true;
/* else fall through to check args */
}
if (IsA(node, NullIfExpr))
{
NullIfExpr *expr = (NullIfExpr *) node;
if (op_volatile(expr->opno) != PROVOLATILE_IMMUTABLE)
return true;
/* else fall through to check args */
}
if (IsA(node, SubLink))
{
SubLink *sublink = (SubLink *) node;
@@ -626,6 +632,14 @@ contain_volatile_functions_walker(Node *node, void *context)
return true;
/* else fall through to check args */
}
if (IsA(node, NullIfExpr))
{
NullIfExpr *expr = (NullIfExpr *) node;
if (op_volatile(expr->opno) == PROVOLATILE_VOLATILE)
return true;
/* else fall through to check args */
}
if (IsA(node, SubLink))
{
SubLink *sublink = (SubLink *) node;
@@ -707,6 +721,10 @@ contain_nonstrict_functions_walker(Node *node, void *context)
}
if (IsA(node, CaseExpr))
return true;
if (IsA(node, CoalesceExpr))
return true;
if (IsA(node, NullIfExpr))
return true;
if (IsA(node, NullTest))
return true;
if (IsA(node, BooleanTest))
@@ -1446,6 +1464,39 @@ eval_const_expressions_mutator(Node *node, List *active_fns)
newcase->defresult = (Expr *) defresult;
return (Node *) newcase;
}
if (IsA(node, CoalesceExpr))
{
CoalesceExpr *coalesceexpr = (CoalesceExpr *) node;
CoalesceExpr *newcoalesce;
List *newargs = NIL;
List *arg;
foreach(arg, coalesceexpr->args)
{
Node *e;
e = eval_const_expressions_mutator((Node *) lfirst(arg),
active_fns);
/*
* We can remove null constants from the list.
* For a non-null constant, if it has not been preceded by any
* other non-null-constant expressions then that is the result.
*/
if (IsA(e, Const))
{
if (((Const *) e)->constisnull)
continue; /* drop null constant */
if (newargs == NIL)
return e; /* first expr */
}
newargs = lappend(newargs, e);
}
newcoalesce = makeNode(CoalesceExpr);
newcoalesce->coalescetype = coalesceexpr->coalescetype;
newcoalesce->args = newargs;
return (Node *) newcoalesce;
}
/*
* For any node type not handled above, we recurse using
@@ -2109,6 +2160,10 @@ expression_tree_walker(Node *node,
return true;
}
break;
case T_CoalesceExpr:
return walker(((CoalesceExpr *) node)->args, context);
case T_NullIfExpr:
return walker(((NullIfExpr *) node)->args, context);
case T_NullTest:
return walker(((NullTest *) node)->arg, context);
case T_BooleanTest:
@@ -2481,6 +2536,26 @@ expression_tree_mutator(Node *node,
return (Node *) newnode;
}
break;
case T_CoalesceExpr:
{
CoalesceExpr *coalesceexpr = (CoalesceExpr *) node;
CoalesceExpr *newnode;
FLATCOPY(newnode, coalesceexpr, CoalesceExpr);
MUTATE(newnode->args, coalesceexpr->args, List *);
return (Node *) newnode;
}
break;
case T_NullIfExpr:
{
NullIfExpr *expr = (NullIfExpr *) node;
NullIfExpr *newnode;
FLATCOPY(newnode, expr, NullIfExpr);
MUTATE(newnode->args, expr->args, List *);
return (Node *) newnode;
}
break;
case T_NullTest:
{
NullTest *ntest = (NullTest *) node;