diff options
Diffstat (limited to 'src/include/nodes/relation.h')
| -rw-r--r-- | src/include/nodes/relation.h | 51 |
1 files changed, 33 insertions, 18 deletions
diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h index b6c598ff7cc..0323db0b82f 100644 --- a/src/include/nodes/relation.h +++ b/src/include/nodes/relation.h @@ -62,7 +62,7 @@ typedef struct PlannerGlobal ParamListInfo boundParams; /* Param values provided to planner() */ - List *paramlist; /* to keep track of cross-level Params */ + List *paramlist; /* unused, will be removed in 9.3 */ List *subplans; /* Plans for SubPlan nodes */ @@ -85,6 +85,9 @@ typedef struct PlannerGlobal Index lastRowMarkId; /* highest PlanRowMark ID assigned */ bool transientPlan; /* redo plan when TransactionXmin changes? */ + + /* Added post-release, will be in a saner place in 9.3: */ + int nParamExec; /* number of PARAM_EXEC Params used */ } PlannerGlobal; /* macro for fetching the Plan associated with a SubPlan node */ @@ -213,6 +216,9 @@ typedef struct PlannerInfo /* optional private data for join_search_hook, e.g., GEQO */ void *join_search_private; + + /* Added post-release, will be in a saner place in 9.3: */ + List *plan_params; /* list of PlannerParamItems, see below */ } PlannerInfo; @@ -1349,22 +1355,25 @@ typedef struct PlaceHolderInfo } 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 - * of subqueries (for the results of a subplan). The n'th entry in the list - * (n counts from 0) corresponds to Param->paramid = n. + * At runtime, PARAM_EXEC slots are used to pass values around from one plan + * node to another. They can be used to pass values down into subqueries (for + * outer references in subqueries), or up out of subqueries (for the results + * of a subplan). + * The planner is responsible for assigning nonconflicting PARAM_EXEC IDs to + * the PARAM_EXEC Params it generates. * - * Each paramlist item shows the absolute query level it is associated with, - * where the outermost query is level 1 and nested subqueries have higher - * numbers. The item the parameter slot represents can be one of four kinds: + * Outer references are managed via root->plan_params, which is a list of + * PlannerParamItems. While planning a subquery, each parent query level's + * plan_params contains the values required from it by the current subquery. * - * A Var: the slot represents a variable of that level that must be passed + * The item a PlannerParamItem represents can be one of three kinds: + * + * A Var: the slot represents a variable of this level that must be passed * down because subqueries have outer references to it. The varlevelsup * value in the Var will always be zero. * * A PlaceHolderVar: this works much like the Var case, except that the - * entry is a PlaceHolderVar node with a contained expression. The PHV + * entry is a PlaceHolderVar node with a contained expression. The PHV * will have phlevelsup = 0, and the contained expression is adjusted * to match in level. * @@ -1373,19 +1382,25 @@ typedef struct PlaceHolderInfo * subquery. The Aggref itself has agglevelsup = 0, and its argument tree * is adjusted to match in level. * - * A Param: the slot holds the result of a subplan (it is a setParam item - * for that subplan). The absolute level shown for such items corresponds - * to the parent query of the subplan. - * * Note: we detect duplicate Var and PlaceHolderVar parameters and coalesce - * them into one slot, but we do not do this for Aggref or Param slots. + * them into one slot, but we do not bother to do that for Aggrefs. + * The scope of duplicate-elimination only extends across the set of + * parameters passed from one query level into a single subquery. So there is + * no possibility of a PARAM_EXEC slot being used for conflicting purposes. + * + * In addition, PARAM_EXEC slots are assigned for Params representing outputs + * from subplans (values that are setParam items for those subplans). These + * IDs need not be tracked via PlannerParamItems, since we do not need any + * duplicate-elimination nor later processing of the represented expressions. + * Instead, we just record the assignment of the slot number by incrementing + * root->glob->nParamExec. */ typedef struct PlannerParamItem { NodeTag type; - Node *item; /* the Var, PlaceHolderVar, Aggref, or Param */ - Index abslevel; /* its absolute query level */ + Node *item; /* the Var, PlaceHolderVar, or Aggref */ + int paramId; /* its assigned PARAM_EXEC slot number */ } PlannerParamItem; #endif /* RELATION_H */ |