diff options
Diffstat (limited to 'src/include/nodes/primnodes.h')
| -rw-r--r-- | src/include/nodes/primnodes.h | 87 |
1 files changed, 84 insertions, 3 deletions
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h index 0ef350687dc..bc17773642c 100644 --- a/src/include/nodes/primnodes.h +++ b/src/include/nodes/primnodes.h @@ -1,13 +1,16 @@ /*------------------------------------------------------------------------- * * primnodes.h - * Definitions for parse tree/query tree ("primitive") nodes. + * Definitions for "primitive" node types, those that are used in more + * than one of the parse/plan/execute stages of the query pipeline. + * Currently, these are mostly nodes for executable expressions + * and join trees. * * * Portions Copyright (c) 1996-2000, PostgreSQL, Inc * Portions Copyright (c) 1994, Regents of the University of California * - * $Id: primnodes.h,v 1.47 2000/08/24 03:29:13 tgl Exp $ + * $Id: primnodes.h,v 1.48 2000/09/12 21:07:10 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -98,6 +101,12 @@ typedef struct Fjoin BoolPtr fj_alwaysDone; } Fjoin; + +/* ---------------------------------------------------------------- + * node types for executable expressions + * ---------------------------------------------------------------- + */ + /* ---------------- * Expr * typeOid - oid of the type of this expression @@ -155,7 +164,7 @@ typedef struct Var AttrNumber varattno; Oid vartype; int32 vartypmod; - Index varlevelsup; /* erased by upper optimizer */ + Index varlevelsup; Index varnoold; /* mainly for debugging --- see above */ AttrNumber varoattno; } Var; @@ -480,4 +489,76 @@ typedef struct RelabelType int32 resulttypmod; } RelabelType; + +/* ---------------------------------------------------------------- + * node types for join trees + * + * The leaves of a join tree structure are RangeTblRef nodes. Above + * these, JoinExpr nodes can appear to denote a specific kind of join + * or qualified join. A join tree can also contain List nodes --- a list + * implies an unqualified cross-product join of its members. The planner + * is allowed to combine the elements of a list using whatever join order + * seems good to it. At present, JoinExpr nodes are always joined in + * exactly the order implied by the tree structure (except the planner + * may choose to swap inner and outer members of a join pair). + * + * NOTE: currently, the planner only supports a List at the top level of + * a join tree. Should generalize this to allow Lists at lower levels. + * + * NOTE: the qualification expressions present in JoinExpr nodes are + * *in addition to* the query's main WHERE clause. For outer joins there + * is a real semantic difference between a join qual and a WHERE clause, + * though if all joins are inner joins they are interchangeable. + * + * NOTE: in the raw output of gram.y, a join tree contains RangeVar and + * RangeSubselect nodes, which are both replaced by RangeTblRef nodes + * during the parse analysis phase. + * ---------------------------------------------------------------- + */ + +/* + * RangeTblRef - reference to an entry in the query's rangetable + * + * We could use direct pointers to the RT entries and skip having these + * nodes, but multiple pointers to the same node in a querytree cause + * lots of headaches, so it seems better to store an index into the RT. + */ +typedef struct RangeTblRef +{ + NodeTag type; + int rtindex; +} RangeTblRef; + +/*---------- + * JoinExpr - for SQL JOIN expressions + * + * isNatural, using, and quals are interdependent. The user can write only + * one of NATURAL, USING(), or ON() (this is enforced by the grammar). + * If he writes NATURAL then parse analysis generates the equivalent USING() + * list, and from that fills in "quals" with the right equality comparisons. + * If he writes USING() then "quals" is filled with equality comparisons. + * If he writes ON() then only "quals" is set. Note that NATURAL/USING + * are not equivalent to ON() since they also affect the output column list. + * + * alias is an Attr node representing the AS alias-clause attached to the + * join expression, or NULL if no clause. During parse analysis, colnames + * is filled with a list of String nodes giving the column names (real or + * alias) of the output of the join, and colvars is filled with a list of + * expressions that can be copied to reference the output columns. + *---------- + */ +typedef struct JoinExpr +{ + NodeTag type; + JoinType jointype; /* type of join */ + bool isNatural; /* Natural join? Will need to shape table */ + Node *larg; /* left subtree */ + Node *rarg; /* right subtree */ + List *using; /* USING clause, if any (list of String) */ + Node *quals; /* qualifiers on join, if any */ + struct Attr *alias; /* user-written alias clause, if any */ + List *colnames; /* output column names (list of String) */ + List *colvars; /* output column nodes (list of expressions) */ +} JoinExpr; + #endif /* PRIMNODES_H */ |