diff options
Diffstat (limited to 'src/include/utils/plancache.h')
| -rw-r--r-- | src/include/utils/plancache.h | 156 |
1 files changed, 96 insertions, 60 deletions
diff --git a/src/include/utils/plancache.h b/src/include/utils/plancache.h index b8639a59a0e..c8c27bbb207 100644 --- a/src/include/utils/plancache.h +++ b/src/include/utils/plancache.h @@ -18,26 +18,47 @@ #include "access/tupdesc.h" #include "nodes/params.h" +#define CACHEDPLANSOURCE_MAGIC 195726186 +#define CACHEDPLAN_MAGIC 953717834 + /* - * CachedPlanSource represents the portion of a cached plan that persists - * across invalidation/replan cycles. It stores a raw parse tree (required), - * the original source text (also required, as of 8.4), and adjunct data. + * CachedPlanSource (which might better have been called CachedQuery) + * represents a SQL query that we expect to use multiple times. It stores + * the query source text, the raw parse tree, and the analyzed-and-rewritten + * query tree, as well as adjunct data. Cache invalidation can happen as a + * result of DDL affecting objects used by the query. In that case we discard + * the analyzed-and-rewritten query tree, and rebuild it when next needed. + * + * An actual execution plan, represented by CachedPlan, is derived from the + * CachedPlanSource when we need to execute the query. The plan could be + * either generic (usable with any set of plan parameters) or custom (for a + * specific set of parameters). plancache.c contains the logic that decides + * which way to do it for any particular execution. If we are using a generic + * cached plan then it is meant to be re-used across multiple executions, so + * callers must always treat CachedPlans as read-only. + * + * Once successfully built and "saved", CachedPlanSources typically live + * for the life of the backend, although they can be dropped explicitly. + * CachedPlans are reference-counted and go away automatically when the last + * reference is dropped. A CachedPlan can outlive the CachedPlanSource it + * was created from. * - * Normally, both the struct itself and the subsidiary data live in the - * context denoted by the context field, while the linked-to CachedPlan, if - * any, has its own context. Thus an invalidated CachedPlan can be dropped - * when no longer needed, and conversely a CachedPlanSource can be dropped - * without worrying whether any portals depend on particular instances of - * its plan. + * An "unsaved" CachedPlanSource can be used for generating plans, but it + * lives in transient storage and will not be updated in response to sinval + * events. * - * But for entries created by FastCreateCachedPlan, the CachedPlanSource - * and the initial version of the CachedPlan share the same memory context. - * In this case, we treat the memory context as belonging to the CachedPlan. - * The CachedPlanSource has an extra reference-counted link (orig_plan) - * to the CachedPlan, and the memory context goes away when the CachedPlan's - * reference count goes to zero. This arrangement saves overhead for plans - * that aren't expected to live long enough to need replanning, while not - * losing any flexibility if a replan turns out to be necessary. + * CachedPlans made from saved CachedPlanSources are likewise in permanent + * storage, so to avoid memory leaks, the reference-counted references to them + * must be held in permanent data structures or ResourceOwners. CachedPlans + * made from unsaved CachedPlanSources are in children of the caller's + * memory context, so references to them should not be longer-lived than + * that context. (Reference counting is somewhat pro forma in that case, + * though it may be useful if the CachedPlan can be discarded early.) + * + * A CachedPlanSource has two associated memory contexts: one that holds the + * struct itself, the query source text and the raw parse tree, and another + * context that holds the rewritten query tree and associated data. This + * allows the query tree to be discarded easily when it is invalidated. * * Note: the string referenced by commandTag is not subsidiary storage; * it is assumed to be a compile-time-constant string. As with portals, @@ -46,78 +67,93 @@ */ typedef struct CachedPlanSource { + int magic; /* should equal CACHEDPLANSOURCE_MAGIC */ Node *raw_parse_tree; /* output of raw_parser() */ - char *query_string; /* text of query (as of 8.4, never NULL) */ + char *query_string; /* source text of query */ const char *commandTag; /* command tag (a constant!), or NULL */ Oid *param_types; /* array of parameter type OIDs, or NULL */ int num_params; /* length of param_types array */ ParserSetupHook parserSetup; /* alternative parameter spec method */ void *parserSetupArg; int cursor_options; /* cursor options used for planning */ - bool fully_planned; /* do we cache planner or rewriter output? */ bool fixed_result; /* disallow change in result tupdesc? */ - struct OverrideSearchPath *search_path; /* saved search_path */ - int generation; /* counter, starting at 1, for replans */ TupleDesc resultDesc; /* result type; NULL = doesn't return tuples */ - struct CachedPlan *plan; /* link to plan, or NULL if not valid */ - MemoryContext context; /* context containing this CachedPlanSource */ - struct CachedPlan *orig_plan; /* link to plan owning my context */ + struct OverrideSearchPath *search_path; /* saved search_path */ + MemoryContext context; /* memory context holding all above */ + /* These fields describe the current analyzed-and-rewritten query tree: */ + List *query_list; /* list of Query nodes, or NIL if not valid */ + List *relationOids; /* OIDs of relations the queries depend on */ + List *invalItems; /* other dependencies, as PlanInvalItems */ + MemoryContext query_context; /* context holding the above, or NULL */ + /* If we have a generic plan, this is a reference-counted link to it: */ + struct CachedPlan *gplan; /* generic plan, or NULL if not valid */ + /* Some state flags: */ + bool is_complete; /* has CompleteCachedPlan been done? */ + bool is_saved; /* has CachedPlanSource been "saved"? */ + bool is_valid; /* is the query_list currently valid? */ + int generation; /* increments each time we create a plan */ + /* If CachedPlanSource has been saved, it is a member of a global list */ + struct CachedPlanSource *next_saved; /* list link, if so */ + /* State kept to help decide whether to use custom or generic plans: */ + double generic_cost; /* cost of generic plan, or -1 if not known */ + double total_custom_cost; /* total cost of custom plans so far */ + int num_custom_plans; /* number of plans included in total */ } CachedPlanSource; /* - * CachedPlan represents the portion of a cached plan that is discarded when - * invalidation occurs. The reference count includes both the link(s) from the - * parent CachedPlanSource, and any active plan executions, so the plan can be - * discarded exactly when refcount goes to zero. Both the struct itself and - * the subsidiary data live in the context denoted by the context field. + * CachedPlan represents an execution plan derived from a CachedPlanSource. + * The reference count includes both the link from the parent CachedPlanSource + * (if any), and any active plan executions, so the plan can be discarded + * exactly when refcount goes to zero. Both the struct itself and the + * subsidiary data live in the context denoted by the context field. * This makes it easy to free a no-longer-needed cached plan. */ typedef struct CachedPlan { - List *stmt_list; /* list of statement or Query nodes */ - bool fully_planned; /* do we cache planner or rewriter output? */ - bool dead; /* if true, do not use */ + int magic; /* should equal CACHEDPLAN_MAGIC */ + List *stmt_list; /* list of statement nodes (PlannedStmts + * and bare utility statements) */ + bool is_saved; /* is CachedPlan in a long-lived context? */ + bool is_valid; /* is the stmt_list currently valid? */ TransactionId saved_xmin; /* if valid, replan when TransactionXmin * changes from this value */ + int generation; /* parent's generation number for this plan */ int refcount; /* count of live references to this struct */ - int generation; /* counter, starting at 1, for replans */ MemoryContext context; /* context containing this CachedPlan */ - /* These fields are used only in the not-fully-planned case: */ - List *relationOids; /* OIDs of relations the stmts depend on */ - List *invalItems; /* other dependencies, as PlanInvalItems */ } CachedPlan; extern void InitPlanCache(void); +extern void ResetPlanCache(void); + extern CachedPlanSource *CreateCachedPlan(Node *raw_parse_tree, const char *query_string, - const char *commandTag, - Oid *param_types, - int num_params, - int cursor_options, - List *stmt_list, - bool fully_planned, - bool fixed_result); -extern CachedPlanSource *FastCreateCachedPlan(Node *raw_parse_tree, - char *query_string, - const char *commandTag, - Oid *param_types, - int num_params, - int cursor_options, - List *stmt_list, - bool fully_planned, - bool fixed_result, - MemoryContext context); -extern void CachedPlanSetParserHook(CachedPlanSource *plansource, + const char *commandTag); +extern void CompleteCachedPlan(CachedPlanSource *plansource, + List *querytree_list, + MemoryContext querytree_context, + Oid *param_types, + int num_params, ParserSetupHook parserSetup, - void *parserSetupArg); + void *parserSetupArg, + int cursor_options, + bool fixed_result); + +extern void SaveCachedPlan(CachedPlanSource *plansource); extern void DropCachedPlan(CachedPlanSource *plansource); -extern CachedPlan *RevalidateCachedPlan(CachedPlanSource *plansource, - bool useResOwner); -extern void ReleaseCachedPlan(CachedPlan *plan, bool useResOwner); + +extern void CachedPlanSetParentContext(CachedPlanSource *plansource, + MemoryContext newcontext); + +extern CachedPlanSource *CopyCachedPlan(CachedPlanSource *plansource); + extern bool CachedPlanIsValid(CachedPlanSource *plansource); -extern TupleDesc PlanCacheComputeResultDesc(List *stmt_list); -extern void ResetPlanCache(void); +extern List *CachedPlanGetTargetList(CachedPlanSource *plansource); + +extern CachedPlan *GetCachedPlan(CachedPlanSource *plansource, + ParamListInfo boundParams, + bool useResOwner); +extern void ReleaseCachedPlan(CachedPlan *plan, bool useResOwner); #endif /* PLANCACHE_H */ |