diff options
Diffstat (limited to 'src/include/nodes/primnodes.h')
| -rw-r--r-- | src/include/nodes/primnodes.h | 35 |
1 files changed, 27 insertions, 8 deletions
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h index e2ef42218fc..2d585bdcc5a 100644 --- a/src/include/nodes/primnodes.h +++ b/src/include/nodes/primnodes.h @@ -6,7 +6,7 @@ * * Copyright (c) 1994, Regents of the University of California * - * $Id: primnodes.h,v 1.36 1999/08/25 23:21:36 tgl Exp $ + * $Id: primnodes.h,v 1.37 1999/11/15 02:00:15 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -98,8 +98,7 @@ typedef struct Fjoin * Expr * typeOid - oid of the type of this expression * opType - type of this expression - * oper - the Oper node if it is an OPER_EXPR or the - * Func node if it is a FUNC_EXPR + * oper - operator node if needed (Oper, Func, or SubPlan) * args - arguments to this expression * ---------------- */ @@ -318,12 +317,31 @@ typedef struct Aggref /* ---------------- * SubLink - * subLinkType - EXISTS, ALL, ANY, EXPR - * useor - TRUE for <> (combine op results with "or" not "and") + * subLinkType - EXISTS, ALL, ANY, MULTIEXPR, EXPR + * useor - TRUE to combine column results with "OR" not "AND" * lefthand - list of outer-query expressions on the left - * oper - list of Oper nodes + * oper - list of Oper nodes for combining operators * subselect - subselect as Query* or parsetree * + * A SubLink represents a subselect appearing in an expression, and in some + * cases also the combining operator(s) just above it. The subLinkType + * indicates the form of the expression represented: + * EXISTS_SUBLINK EXISTS(SELECT ...) + * ALL_SUBLINK (lefthand) op ALL (SELECT ...) + * ANY_SUBLINK (lefthand) op ANY (SELECT ...) + * MULTIEXPR_SUBLINK (lefthand) op (SELECT ...) + * EXPR_SUBLINK (SELECT with single targetlist item ...) + * For ALL, ANY, and MULTIEXPR, the lefthand is a list of expressions of the + * same length as the subselect's targetlist. MULTIEXPR will *always* have + * a list with more than one entry; if the subselect has just one target + * then the parser will create an EXPR_SUBLINK instead (and any operator + * above the subselect will be represented separately). Note that both + * MULTIEXPR and EXPR require the subselect to deliver only one row. + * ALL, ANY, and MULTIEXPR require the combining operators to deliver boolean + * results. These are reduced to one result per row using OR or AND semantics + * depending on the "useor" flag. ALL and ANY combine the per-row results + * using AND and OR semantics respectively. + * * 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 @@ -348,12 +366,13 @@ typedef struct Aggref * 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. + * In EXISTS and EXPR SubLinks, both lefthand and oper are unused and are + * always NIL. useor is not significant either for these sublink types. * ---------------- */ typedef enum SubLinkType { - EXISTS_SUBLINK, ALL_SUBLINK, ANY_SUBLINK, EXPR_SUBLINK + EXISTS_SUBLINK, ALL_SUBLINK, ANY_SUBLINK, MULTIEXPR_SUBLINK, EXPR_SUBLINK } SubLinkType; |