diff options
Diffstat (limited to 'src/include/nodes/relation.h')
| -rw-r--r-- | src/include/nodes/relation.h | 63 |
1 files changed, 58 insertions, 5 deletions
diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h index 9934daa64a..b5eb00a7a6 100644 --- a/src/include/nodes/relation.h +++ b/src/include/nodes/relation.h @@ -7,7 +7,7 @@ * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.161 2008/10/17 20:23:45 tgl Exp $ + * $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.162 2008/10/21 20:42:53 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -76,6 +76,8 @@ typedef struct PlannerGlobal List *invalItems; /* other dependencies, as PlanInvalItems */ + Index lastPHId; /* highest PlaceHolderVar ID assigned */ + bool transientPlan; /* redo plan when TransactionXmin changes? */ } PlannerGlobal; @@ -163,6 +165,8 @@ typedef struct PlannerInfo List *append_rel_list; /* list of AppendRelInfos */ + List *placeholder_list; /* list of PlaceHolderInfos */ + List *query_pathkeys; /* desired pathkeys for query_planner(), and * actual pathkeys afterwards */ @@ -243,11 +247,12 @@ typedef struct PlannerInfo * clauses have been applied (ie, output rows of a plan for it) * width - avg. number of bytes per tuple in the relation after the * appropriate projections have been done (ie, output width) - * reltargetlist - List of Var nodes for the attributes we need to - * output from this relation (in no particular order, - * but all rels of an appendrel set must use same order) + * reltargetlist - List of Var and PlaceHolderVar nodes for the values + * we need to output from this relation. + * List is in no particular order, but all rels of an + * appendrel set must use corresponding orders. * NOTE: in a child relation, may contain RowExpr or - * ConvertRowtypeExpr representing a whole-row Var + * ConvertRowtypeExpr representing a whole-row Var. * pathlist - List of Path nodes, one for each potentially useful * method of generating the relation * cheapest_startup_path - the pathlist member with lowest startup cost @@ -1090,6 +1095,29 @@ typedef struct FlattenedSubLink } FlattenedSubLink; /* + * Placeholder node for an expression to be evaluated below the top level + * of a plan tree. This is used during planning to represent the contained + * expression. At the end of the planning process it is replaced by either + * the contained expression or a Var referring to a lower-level evaluation of + * the contained expression. Typically the evaluation occurs below an outer + * join, and Var references above the outer join might thereby yield NULL + * instead of the expression value. + * + * Although the planner treats this as an expression node type, it is not + * recognized by the parser or executor, so we declare it here rather than + * in primnodes.h. + */ + +typedef struct PlaceHolderVar +{ + Expr xpr; + Expr *phexpr; /* the represented expression */ + Relids phrels; /* base relids syntactically within expr src */ + Index phid; /* ID for PHV (unique within planner run) */ + Index phlevelsup; /* > 0 if PHV belongs to outer query */ +} PlaceHolderVar; + +/* * "Special join" info. * * One-sided outer joins constrain the order of joining partially but not @@ -1251,6 +1279,31 @@ typedef struct AppendRelInfo } AppendRelInfo; /* + * For each distinct placeholder expression generated during planning, we + * store a PlaceHolderInfo node in the PlannerInfo node's placeholder_list. + * This stores info that is needed centrally rather than in each copy of the + * PlaceHolderVar. The phid fields identify which PlaceHolderInfo goes with + * each PlaceHolderVar. Note that phid is unique throughout a planner run, + * not just within a query level --- this is so that we need not reassign ID's + * when pulling a subquery into its parent. + * + * The idea is to evaluate the expression at (only) the ph_eval_at join level, + * then allow it to bubble up like a Var until the ph_needed join level. + * ph_needed has the same definition as attr_needed for a regular Var. + */ + +typedef struct PlaceHolderInfo +{ + NodeTag type; + + Index phid; /* ID for PH (unique within planner run) */ + PlaceHolderVar *ph_var; /* copy of PlaceHolderVar tree */ + Relids ph_eval_at; /* lowest level we can evaluate value at */ + Relids ph_needed; /* highest level the value is needed at */ + int32 ph_width; /* estimated attribute width */ +} PlaceHolderInfo; + +/* * glob->paramlist keeps track of the PARAM_EXEC slots that we have decided * we need for the query. At runtime these slots are used to pass values * either down into subqueries (for outer references in subqueries) or up out |