diff options
Diffstat (limited to 'src/include/nodes/primnodes.h')
| -rw-r--r-- | src/include/nodes/primnodes.h | 88 |
1 files changed, 49 insertions, 39 deletions
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h index 01a6dbf8d64..285a0008fdc 100644 --- a/src/include/nodes/primnodes.h +++ b/src/include/nodes/primnodes.h @@ -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 1.74 2002/12/13 19:46:00 tgl Exp $ + * $Id: primnodes.h,v 1.75 2002/12/14 00:17:59 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -378,32 +378,21 @@ typedef struct BoolExpr * using AND and OR semantics respectively. * * SubLink is classed as an Expr node, but it is not actually executable; - * it must be replaced in the expression tree by a SubPlanExpr node during + * it must be replaced in the expression tree by a SubPlan node during * planning. * - * 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 single A_Expr (not a list!) containing - * the string name of the operator, but no arguments. - * 2. The parser's expression transformation transforms lefthand normally, - * and replaces oper with a list of OpExpr 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 complete Expr trees for - * these operations yet: the args fields of the OpExpr nodes are NIL. - * 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 OpExpr - * 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 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 SubPlanExpr nodes. + * NOTE: in the raw output of gram.y, lefthand contains a list of (raw) + * expressions, and oper contains a single A_Expr (not a list!) containing + * the string name of the operator, but no arguments. Also, subselect is + * a raw parsetree. During parse analysis, the parser transforms the + * lefthand expression list using normal expression transformation rules. + * It replaces oper with a list of OpExpr 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 complete Expr trees for these operations yet: + * the args fields of the OpExpr nodes are NIL. And subselect is transformed + * to a Query. This is the representation seen in saved rules and in the + * rewriter. * * In EXISTS and EXPR SubLinks, both lefthand and oper are unused and are * always NIL. useor is not significant either for these sublink types. @@ -423,37 +412,58 @@ typedef struct SubLink * "OR" not "AND" */ List *lefthand; /* list of outer-query expressions on the * left */ - List *oper; /* list of OpExpr nodes for combining - * operators, or final list of executable - * expressions */ + List *oper; /* list of arg-less OpExpr nodes for + * combining operators */ Node *subselect; /* subselect as Query* or parsetree */ } SubLink; /* - * SubPlanExpr - executable expression node for a subplan (sub-SELECT) - * - * The planner replaces SubLink nodes in expression trees with SubPlanExpr - * nodes after it has finished planning the subquery. See notes above. - */ -typedef struct SubPlanExpr + * SubPlan - executable expression node for a subplan (sub-SELECT) + * + * The planner replaces SubLink nodes in expression trees with SubPlan + * nodes after it has finished planning the subquery. SubPlan contains + * a sub-plantree and rtable instead of a sub-Query. Its "oper" field + * corresponds to the original SubLink's oper list, but has been expanded + * into valid executable expressions representing the application of the + * combining operator(s) to the lefthand expressions and values from the + * inner targetlist. The original lefthand expressions now appear as + * left-hand arguments of the OpExpr nodes, while the inner targetlist items + * are represented by PARAM_EXEC Param nodes. (Note: if the sub-select + * becomes an InitPlan rather than a SubPlan, the rebuilt oper list is + * part of the outer plan tree and so is not stored in the oper field.) + * + * The planner also derives lists of the values that need to be passed into + * and out of the subplan. Input values are represented as a list "args" of + * expressions to be evaluated in the outer-query context (currently these + * args are always just Vars, but in principle they could be any expression). + * The values are assigned to the global PARAM_EXEC params indexed by parParam + * (the parParam and args lists must have the same length). setParam is a + * list of the PARAM_EXEC params that are computed by the sub-select, if it + * is an initPlan. + */ +typedef struct SubPlan { Expr xpr; - Oid typeOid; /* PG_TYPE OID of the expression result */ + /* Fields copied from original SubLink: */ + SubLinkType subLinkType; /* EXISTS, ALL, ANY, MULTIEXPR, EXPR */ + bool useor; /* TRUE to combine column results with + * "OR" not "AND" */ + List *oper; /* list of executable expressions for + * combining operators (with arguments) */ + /* The subselect, transformed to a Plan: */ struct Plan *plan; /* subselect plan itself */ int plan_id; /* dummy thing because of we haven't equal * funcs for plan nodes... actually, we * could put *plan itself somewhere else * (TopPlan node ?)... */ List *rtable; /* range table for subselect */ + /* Information for passing params into and out of the subselect: */ /* setParam and parParam are lists of integers (param IDs) */ List *setParam; /* non-correlated EXPR & EXISTS subqueries * have to set some Params for paren Plan */ List *parParam; /* indices of input Params from parent plan */ List *args; /* exprs to pass as parParam values */ - SubLink *sublink; /* SubLink node from parser; holds info - * about what to do with subselect's - * results */ -} SubPlanExpr; +} SubPlan; /* ---------------- * FieldSelect |