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Code review for IS DISTINCT FROM patch. Fix incorrect constant-folding

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logic, dissuade planner from thinking that 'x IS DISTINCT FROM 42' may
be optimized into 'x = 42' (!!), cause dependency on = operator to be
recorded correctly, minor other improvements.
This commit is contained in:
Tom Lane
2002-11-30 21:25:08 +00:00
parent 36c356e799
commit 2b7ec402c4
7 changed files with 70 additions and 115 deletions
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10
src/include/nodes/primnodes.h
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@@ -10,7 +10,7 @@
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: primnodes.h,v 1.70 2002/11/26 03:01:59 tgl Exp $
* $Id: primnodes.h,v 1.71 2002/11/30 21:25:06 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -165,6 +165,12 @@ typedef enum CoercionForm
/*
* Expr
*
* Note: DISTINCT_EXPR implements the "x IS DISTINCT FROM y" construct.
* This is similar to an OP_EXPR, except for its handling of NULL inputs.
* The oper field is always an Oper node for the "=" operator for x and y.
* (We use "=", not the more obvious "<>", because more datatypes have "="
* than "<>". This means the executor must invert the operator result.)
*/
typedef enum OpType
{
@@ -183,7 +189,7 @@ typedef struct Expr
} Expr;
/*
* Oper - Expr subnode for an OP_EXPR
* Oper - Expr subnode for an OP_EXPR (or DISTINCT_EXPR)
*
* NOTE: in the good old days 'opno' used to be both (or either, or
* neither) the pg_operator oid, and/or the pg_proc oid depending