1 /*------------------------------------------------------------------------- 2 * 3 * plancache.h 4 * Plan cache definitions. 5 * 6 * See plancache.c for comments. 7 * 8 * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group 9 * Portions Copyright (c) 1994, Regents of the University of California 10 * 11 * src/include/utils/plancache.h 12 * 13 *------------------------------------------------------------------------- 14 */ 15 #ifndef PLANCACHE_H 16 #define PLANCACHE_H 17 18 #include "access/tupdesc.h" 19 #include "nodes/params.h" 20 21 #define CACHEDPLANSOURCE_MAGIC 195726186 22 #define CACHEDPLAN_MAGIC 953717834 23 24 /* 25 * CachedPlanSource (which might better have been called CachedQuery) 26 * represents a SQL query that we expect to use multiple times. It stores 27 * the query source text, the raw parse tree, and the analyzed-and-rewritten 28 * query tree, as well as adjunct data. Cache invalidation can happen as a 29 * result of DDL affecting objects used by the query. In that case we discard 30 * the analyzed-and-rewritten query tree, and rebuild it when next needed. 31 * 32 * An actual execution plan, represented by CachedPlan, is derived from the 33 * CachedPlanSource when we need to execute the query. The plan could be 34 * either generic (usable with any set of plan parameters) or custom (for a 35 * specific set of parameters). plancache.c contains the logic that decides 36 * which way to do it for any particular execution. If we are using a generic 37 * cached plan then it is meant to be re-used across multiple executions, so 38 * callers must always treat CachedPlans as read-only. 39 * 40 * Once successfully built and "saved", CachedPlanSources typically live 41 * for the life of the backend, although they can be dropped explicitly. 42 * CachedPlans are reference-counted and go away automatically when the last 43 * reference is dropped. A CachedPlan can outlive the CachedPlanSource it 44 * was created from. 45 * 46 * An "unsaved" CachedPlanSource can be used for generating plans, but it 47 * lives in transient storage and will not be updated in response to sinval 48 * events. 49 * 50 * CachedPlans made from saved CachedPlanSources are likewise in permanent 51 * storage, so to avoid memory leaks, the reference-counted references to them 52 * must be held in permanent data structures or ResourceOwners. CachedPlans 53 * made from unsaved CachedPlanSources are in children of the caller's 54 * memory context, so references to them should not be longer-lived than 55 * that context. (Reference counting is somewhat pro forma in that case, 56 * though it may be useful if the CachedPlan can be discarded early.) 57 * 58 * A CachedPlanSource has two associated memory contexts: one that holds the 59 * struct itself, the query source text and the raw parse tree, and another 60 * context that holds the rewritten query tree and associated data. This 61 * allows the query tree to be discarded easily when it is invalidated. 62 * 63 * Some callers wish to use the CachedPlan API even with one-shot queries 64 * that have no reason to be saved at all. We therefore support a "oneshot" 65 * variant that does no data copying or invalidation checking. In this case 66 * there are no separate memory contexts: the CachedPlanSource struct and 67 * all subsidiary data live in the caller's CurrentMemoryContext, and there 68 * is no way to free memory short of clearing that entire context. A oneshot 69 * plan is always treated as unsaved. 70 * 71 * Note: the string referenced by commandTag is not subsidiary storage; 72 * it is assumed to be a compile-time-constant string. As with portals, 73 * commandTag shall be NULL if and only if the original query string (before 74 * rewriting) was an empty string. 75 */ 76 typedef struct CachedPlanSource 77 { 78 int magic; /* should equal CACHEDPLANSOURCE_MAGIC */ 79 Node *raw_parse_tree; /* output of raw_parser(), or NULL */ 80 const char *query_string; /* source text of query */ 81 const char *commandTag; /* command tag (a constant!), or NULL */ 82 Oid *param_types; /* array of parameter type OIDs, or NULL */ 83 int num_params; /* length of param_types array */ 84 ParserSetupHook parserSetup; /* alternative parameter spec method */ 85 void *parserSetupArg; 86 int cursor_options; /* cursor options used for planning */ 87 bool fixed_result; /* disallow change in result tupdesc? */ 88 TupleDesc resultDesc; /* result type; NULL = doesn't return tuples */ 89 MemoryContext context; /* memory context holding all above */ 90 /* These fields describe the current analyzed-and-rewritten query tree: */ 91 List *query_list; /* list of Query nodes, or NIL if not valid */ 92 List *relationOids; /* OIDs of relations the queries depend on */ 93 List *invalItems; /* other dependencies, as PlanInvalItems */ 94 struct OverrideSearchPath *search_path; /* search_path used for 95 * parsing and planning */ 96 MemoryContext query_context; /* context holding the above, or NULL */ 97 Oid rewriteRoleId; /* Role ID we did rewriting for */ 98 bool rewriteRowSecurity; /* row_security used during rewrite */ 99 bool dependsOnRLS; /* is rewritten query specific to the above? */ 100 /* If we have a generic plan, this is a reference-counted link to it: */ 101 struct CachedPlan *gplan; /* generic plan, or NULL if not valid */ 102 /* Some state flags: */ 103 bool is_oneshot; /* is it a "oneshot" plan? */ 104 bool is_complete; /* has CompleteCachedPlan been done? */ 105 bool is_saved; /* has CachedPlanSource been "saved"? */ 106 bool is_valid; /* is the query_list currently valid? */ 107 int generation; /* increments each time we create a plan */ 108 /* If CachedPlanSource has been saved, it is a member of a global list */ 109 struct CachedPlanSource *next_saved; /* list link, if so */ 110 /* State kept to help decide whether to use custom or generic plans: */ 111 double generic_cost; /* cost of generic plan, or -1 if not known */ 112 double total_custom_cost; /* total cost of custom plans so far */ 113 int num_custom_plans; /* number of plans included in total */ 114 } CachedPlanSource; 115 116 /* 117 * CachedPlan represents an execution plan derived from a CachedPlanSource. 118 * The reference count includes both the link from the parent CachedPlanSource 119 * (if any), and any active plan executions, so the plan can be discarded 120 * exactly when refcount goes to zero. Both the struct itself and the 121 * subsidiary data live in the context denoted by the context field. 122 * This makes it easy to free a no-longer-needed cached plan. (However, 123 * if is_oneshot is true, the context does not belong solely to the CachedPlan 124 * so no freeing is possible.) 125 */ 126 typedef struct CachedPlan 127 { 128 int magic; /* should equal CACHEDPLAN_MAGIC */ 129 List *stmt_list; /* list of statement nodes (PlannedStmts and 130 * bare utility statements) */ 131 bool is_oneshot; /* is it a "oneshot" plan? */ 132 bool is_saved; /* is CachedPlan in a long-lived context? */ 133 bool is_valid; /* is the stmt_list currently valid? */ 134 Oid planRoleId; /* Role ID the plan was created for */ 135 bool dependsOnRole; /* is plan specific to that role? */ 136 TransactionId saved_xmin; /* if valid, replan when TransactionXmin 137 * changes from this value */ 138 int generation; /* parent's generation number for this plan */ 139 int refcount; /* count of live references to this struct */ 140 MemoryContext context; /* context containing this CachedPlan */ 141 } CachedPlan; 142 143 144 extern void InitPlanCache(void); 145 extern void ResetPlanCache(void); 146 147 extern CachedPlanSource *CreateCachedPlan(Node *raw_parse_tree, 148 const char *query_string, 149 const char *commandTag); 150 extern CachedPlanSource *CreateOneShotCachedPlan(Node *raw_parse_tree, 151 const char *query_string, 152 const char *commandTag); 153 extern void CompleteCachedPlan(CachedPlanSource *plansource, 154 List *querytree_list, 155 MemoryContext querytree_context, 156 Oid *param_types, 157 int num_params, 158 ParserSetupHook parserSetup, 159 void *parserSetupArg, 160 int cursor_options, 161 bool fixed_result); 162 163 extern void SaveCachedPlan(CachedPlanSource *plansource); 164 extern void DropCachedPlan(CachedPlanSource *plansource); 165 166 extern void CachedPlanSetParentContext(CachedPlanSource *plansource, 167 MemoryContext newcontext); 168 169 extern CachedPlanSource *CopyCachedPlan(CachedPlanSource *plansource); 170 171 extern bool CachedPlanIsValid(CachedPlanSource *plansource); 172 173 extern List *CachedPlanGetTargetList(CachedPlanSource *plansource); 174 175 extern CachedPlan *GetCachedPlan(CachedPlanSource *plansource, 176 ParamListInfo boundParams, 177 bool useResOwner); 178 extern void ReleaseCachedPlan(CachedPlan *plan, bool useResOwner); 179 180 #endif /* PLANCACHE_H */ 181