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Revise implementation of SubLinks so that there is a consistent,

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documented intepretation of the lefthand and oper fields.  Fix a number of
obscure problems while at it --- for example, the old code failed if the parser
decided to insert a type-coercion function just below the operator of a
SubLink.
CAUTION: this will break stored rules that contain subplans.  You may
need to initdb.
This commit is contained in:
Tom Lane
1999-08-25 23:21:43 +00:00
parent edda70c0de
commit 42af56e1ea
8 changed files with 326 additions and 322 deletions
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32
src/include/nodes/primnodes.h
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@@ -6,7 +6,7 @@
*
* Copyright (c) 1994, Regents of the University of California
*
* $Id: primnodes.h,v 1.35 1999/08/22 20:15:00 tgl Exp $
* $Id: primnodes.h,v 1.36 1999/08/25 23:21:36 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -319,10 +319,36 @@ typedef struct Aggref
/* ----------------
* SubLink
* subLinkType - EXISTS, ALL, ANY, EXPR
* useor - TRUE for <>
* lefthand - list of Var/Const nodes on the left
* useor - TRUE for <> (combine op results with "or" not "and")
* lefthand - list of outer-query expressions on the left
* oper - list of Oper nodes
* subselect - subselect as Query* or parsetree
*
* NOTE: lefthand and oper have varying meanings depending on where you look
* in the parse/plan pipeline:
* 1. gram.y delivers a list of the (untransformed) lefthand expressions in
* lefthand, and sets oper to a one-element list containing the string
* name of the operator.
* 2. The parser's expression transformation transforms lefthand normally,
* and replaces oper with a list of Oper nodes, one per lefthand
* expression. These nodes represent the parser's resolution of exactly
* which operator to apply to each pair of lefthand and targetlist
* expressions. However, we have not constructed actual Expr trees for
* these operators yet. This is the representation seen in saved rules
* and in the rewriter.
* 3. Finally, the planner converts the oper list to a list of normal Expr
* nodes representing the application of the operator(s) to the lefthand
* expressions and values from the inner targetlist. The inner
* targetlist items are represented by placeholder Param or Const nodes.
* The lefthand field is set to NIL, since its expressions are now in
* the Expr list. This representation is passed to the executor.
*
* Planner routines that might see either representation 2 or 3 can tell
* the difference by checking whether lefthand is NIL or not. Also,
* representation 2 appears in a "bare" SubLink, while representation 3 is
* found in SubLinks that are children of SubPlan nodes.
*
* In an EXISTS SubLink, both lefthand and oper are unused and are always NIL.
* ----------------
*/
typedef enum SubLinkType