diff options
Diffstat (limited to 'src/include/nodes/primnodes.h')
| -rw-r--r-- | src/include/nodes/primnodes.h | 26 |
1 files changed, 24 insertions, 2 deletions
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h index f0c55112cbc..f6da1adbfa0 100644 --- a/src/include/nodes/primnodes.h +++ b/src/include/nodes/primnodes.h @@ -10,7 +10,7 @@ * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $PostgreSQL: pgsql/src/include/nodes/primnodes.h,v 1.138 2008/08/02 21:32:00 tgl Exp $ + * $PostgreSQL: pgsql/src/include/nodes/primnodes.h,v 1.139 2008/08/22 00:16:04 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -445,7 +445,8 @@ typedef struct SubLink * * If the sub-select becomes an initplan rather than a subplan, the executable * expression is part of the outer plan's expression tree (and the SubPlan - * node itself is not). In this case testexpr is NULL to avoid duplication. + * node itself is not, but rather is found in the outer plan's initPlan + * list). In this case testexpr is NULL to avoid duplication. * * 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 @@ -457,6 +458,10 @@ typedef struct SubLink * is an initplan; they are listed in order by sub-select output column * position. (parParam and setParam are integer Lists, not Bitmapsets, * because their ordering is significant.) + * + * Also, the planner computes startup and per-call costs for use of the + * SubPlan. Note that these include the cost of the subquery proper, + * evaluation of the testexpr if any, and any hashtable management overhead. */ typedef struct SubPlan { @@ -482,8 +487,25 @@ typedef struct SubPlan * Params for parent plan */ List *parParam; /* indices of input Params from parent plan */ List *args; /* exprs to pass as parParam values */ + /* Estimated execution costs: */ + Cost startup_cost; /* one-time setup cost */ + Cost per_call_cost; /* cost for each subplan evaluation */ } SubPlan; +/* + * AlternativeSubPlan - expression node for a choice among SubPlans + * + * The subplans are given as a List so that the node definition need not + * change if there's ever more than two alternatives. For the moment, + * though, there are always exactly two; and the first one is the fast-start + * plan. + */ +typedef struct AlternativeSubPlan +{ + Expr xpr; + List *subplans; /* SubPlan(s) with equivalent results */ +} AlternativeSubPlan; + /* ---------------- * FieldSelect * |