1 /*------------------------------------------------------------------------- 2 * 3 * plancache.h 4 * Plan cache definitions. 5 * 6 * See plancache.c for comments. 7 * 8 * Portions Copyright (c) 1996-2020, 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 "lib/ilist.h" 20 #include "nodes/params.h" 21 #include "tcop/cmdtag.h" 22 #include "utils/queryenvironment.h" 23 #include "utils/resowner.h" 24 25 26 /* Forward declaration, to avoid including parsenodes.h here */ 27 struct RawStmt; 28 29 /* possible values for plan_cache_mode */ 30 typedef enum 31 { 32 PLAN_CACHE_MODE_AUTO, 33 PLAN_CACHE_MODE_FORCE_GENERIC_PLAN, 34 PLAN_CACHE_MODE_FORCE_CUSTOM_PLAN 35 } PlanCacheMode; 36 37 /* GUC parameter */ 38 extern int plan_cache_mode; 39 40 #define CACHEDPLANSOURCE_MAGIC 195726186 41 #define CACHEDPLAN_MAGIC 953717834 42 #define CACHEDEXPR_MAGIC 838275847 43 44 /* 45 * CachedPlanSource (which might better have been called CachedQuery) 46 * represents a SQL query that we expect to use multiple times. It stores 47 * the query source text, the raw parse tree, and the analyzed-and-rewritten 48 * query tree, as well as adjunct data. Cache invalidation can happen as a 49 * result of DDL affecting objects used by the query. In that case we discard 50 * the analyzed-and-rewritten query tree, and rebuild it when next needed. 51 * 52 * An actual execution plan, represented by CachedPlan, is derived from the 53 * CachedPlanSource when we need to execute the query. The plan could be 54 * either generic (usable with any set of plan parameters) or custom (for a 55 * specific set of parameters). plancache.c contains the logic that decides 56 * which way to do it for any particular execution. If we are using a generic 57 * cached plan then it is meant to be re-used across multiple executions, so 58 * callers must always treat CachedPlans as read-only. 59 * 60 * Once successfully built and "saved", CachedPlanSources typically live 61 * for the life of the backend, although they can be dropped explicitly. 62 * CachedPlans are reference-counted and go away automatically when the last 63 * reference is dropped. A CachedPlan can outlive the CachedPlanSource it 64 * was created from. 65 * 66 * An "unsaved" CachedPlanSource can be used for generating plans, but it 67 * lives in transient storage and will not be updated in response to sinval 68 * events. 69 * 70 * CachedPlans made from saved CachedPlanSources are likewise in permanent 71 * storage, so to avoid memory leaks, the reference-counted references to them 72 * must be held in permanent data structures or ResourceOwners. CachedPlans 73 * made from unsaved CachedPlanSources are in children of the caller's 74 * memory context, so references to them should not be longer-lived than 75 * that context. (Reference counting is somewhat pro forma in that case, 76 * though it may be useful if the CachedPlan can be discarded early.) 77 * 78 * A CachedPlanSource has two associated memory contexts: one that holds the 79 * struct itself, the query source text and the raw parse tree, and another 80 * context that holds the rewritten query tree and associated data. This 81 * allows the query tree to be discarded easily when it is invalidated. 82 * 83 * Some callers wish to use the CachedPlan API even with one-shot queries 84 * that have no reason to be saved at all. We therefore support a "oneshot" 85 * variant that does no data copying or invalidation checking. In this case 86 * there are no separate memory contexts: the CachedPlanSource struct and 87 * all subsidiary data live in the caller's CurrentMemoryContext, and there 88 * is no way to free memory short of clearing that entire context. A oneshot 89 * plan is always treated as unsaved. 90 * 91 * Note: the string referenced by commandTag is not subsidiary storage; 92 * it is assumed to be a compile-time-constant string. As with portals, 93 * commandTag shall be NULL if and only if the original query string (before 94 * rewriting) was an empty string. 95 */ 96 typedef struct CachedPlanSource 97 { 98 int magic; /* should equal CACHEDPLANSOURCE_MAGIC */ 99 struct RawStmt *raw_parse_tree; /* output of raw_parser(), or NULL */ 100 const char *query_string; /* source text of query */ 101 CommandTag commandTag; /* 'nuff said */ 102 Oid *param_types; /* array of parameter type OIDs, or NULL */ 103 int num_params; /* length of param_types array */ 104 ParserSetupHook parserSetup; /* alternative parameter spec method */ 105 void *parserSetupArg; 106 int cursor_options; /* cursor options used for planning */ 107 bool fixed_result; /* disallow change in result tupdesc? */ 108 TupleDesc resultDesc; /* result type; NULL = doesn't return tuples */ 109 MemoryContext context; /* memory context holding all above */ 110 /* These fields describe the current analyzed-and-rewritten query tree: */ 111 List *query_list; /* list of Query nodes, or NIL if not valid */ 112 List *relationOids; /* OIDs of relations the queries depend on */ 113 List *invalItems; /* other dependencies, as PlanInvalItems */ 114 struct OverrideSearchPath *search_path; /* search_path used for parsing 115 * and planning */ 116 MemoryContext query_context; /* context holding the above, or NULL */ 117 Oid rewriteRoleId; /* Role ID we did rewriting for */ 118 bool rewriteRowSecurity; /* row_security used during rewrite */ 119 bool dependsOnRLS; /* is rewritten query specific to the above? */ 120 /* If we have a generic plan, this is a reference-counted link to it: */ 121 struct CachedPlan *gplan; /* generic plan, or NULL if not valid */ 122 /* Some state flags: */ 123 bool is_oneshot; /* is it a "oneshot" plan? */ 124 bool is_complete; /* has CompleteCachedPlan been done? */ 125 bool is_saved; /* has CachedPlanSource been "saved"? */ 126 bool is_valid; /* is the query_list currently valid? */ 127 int generation; /* increments each time we create a plan */ 128 /* If CachedPlanSource has been saved, it is a member of a global list */ 129 dlist_node node; /* list link, if is_saved */ 130 /* State kept to help decide whether to use custom or generic plans: */ 131 double generic_cost; /* cost of generic plan, or -1 if not known */ 132 double total_custom_cost; /* total cost of custom plans so far */ 133 int num_custom_plans; /* number of plans included in total */ 134 } CachedPlanSource; 135 136 /* 137 * CachedPlan represents an execution plan derived from a CachedPlanSource. 138 * The reference count includes both the link from the parent CachedPlanSource 139 * (if any), and any active plan executions, so the plan can be discarded 140 * exactly when refcount goes to zero. Both the struct itself and the 141 * subsidiary data live in the context denoted by the context field. 142 * This makes it easy to free a no-longer-needed cached plan. (However, 143 * if is_oneshot is true, the context does not belong solely to the CachedPlan 144 * so no freeing is possible.) 145 */ 146 typedef struct CachedPlan 147 { 148 int magic; /* should equal CACHEDPLAN_MAGIC */ 149 List *stmt_list; /* list of PlannedStmts */ 150 bool is_oneshot; /* is it a "oneshot" plan? */ 151 bool is_saved; /* is CachedPlan in a long-lived context? */ 152 bool is_valid; /* is the stmt_list currently valid? */ 153 Oid planRoleId; /* Role ID the plan was created for */ 154 bool dependsOnRole; /* is plan specific to that role? */ 155 TransactionId saved_xmin; /* if valid, replan when TransactionXmin 156 * changes from this value */ 157 int generation; /* parent's generation number for this plan */ 158 int refcount; /* count of live references to this struct */ 159 MemoryContext context; /* context containing this CachedPlan */ 160 } CachedPlan; 161 162 /* 163 * CachedExpression is a low-overhead mechanism for caching the planned form 164 * of standalone scalar expressions. While such expressions are not usually 165 * subject to cache invalidation events, that can happen, for example because 166 * of replacement of a SQL function that was inlined into the expression. 167 * The plancache takes care of storing the expression tree and marking it 168 * invalid if a cache invalidation occurs, but the caller must notice the 169 * !is_valid status and discard the obsolete expression without reusing it. 170 * We do not store the original parse tree, only the planned expression; 171 * this is an optimization based on the assumption that we usually will not 172 * need to replan for the life of the session. 173 */ 174 typedef struct CachedExpression 175 { 176 int magic; /* should equal CACHEDEXPR_MAGIC */ 177 Node *expr; /* planned form of expression */ 178 bool is_valid; /* is the expression still valid? */ 179 /* remaining fields should be treated as private to plancache.c: */ 180 List *relationOids; /* OIDs of relations the expr depends on */ 181 List *invalItems; /* other dependencies, as PlanInvalItems */ 182 MemoryContext context; /* context containing this CachedExpression */ 183 dlist_node node; /* link in global list of CachedExpressions */ 184 } CachedExpression; 185 186 187 extern void InitPlanCache(void); 188 extern void ResetPlanCache(void); 189 190 extern CachedPlanSource *CreateCachedPlan(struct RawStmt *raw_parse_tree, 191 const char *query_string, 192 CommandTag commandTag); 193 extern CachedPlanSource *CreateOneShotCachedPlan(struct RawStmt *raw_parse_tree, 194 const char *query_string, 195 CommandTag commandTag); 196 extern void CompleteCachedPlan(CachedPlanSource *plansource, 197 List *querytree_list, 198 MemoryContext querytree_context, 199 Oid *param_types, 200 int num_params, 201 ParserSetupHook parserSetup, 202 void *parserSetupArg, 203 int cursor_options, 204 bool fixed_result); 205 206 extern void SaveCachedPlan(CachedPlanSource *plansource); 207 extern void DropCachedPlan(CachedPlanSource *plansource); 208 209 extern void CachedPlanSetParentContext(CachedPlanSource *plansource, 210 MemoryContext newcontext); 211 212 extern CachedPlanSource *CopyCachedPlan(CachedPlanSource *plansource); 213 214 extern bool CachedPlanIsValid(CachedPlanSource *plansource); 215 216 extern List *CachedPlanGetTargetList(CachedPlanSource *plansource, 217 QueryEnvironment *queryEnv); 218 219 extern CachedPlan *GetCachedPlan(CachedPlanSource *plansource, 220 ParamListInfo boundParams, 221 bool useResOwner, 222 QueryEnvironment *queryEnv); 223 extern void ReleaseCachedPlan(CachedPlan *plan, bool useResOwner); 224 225 extern bool CachedPlanAllowsSimpleValidityCheck(CachedPlanSource *plansource, 226 CachedPlan *plan, 227 ResourceOwner owner); 228 extern bool CachedPlanIsSimplyValid(CachedPlanSource *plansource, 229 CachedPlan *plan, 230 ResourceOwner owner); 231 232 extern CachedExpression *GetCachedExpression(Node *expr); 233 extern void FreeCachedExpression(CachedExpression *cexpr); 234 235 #endif /* PLANCACHE_H */ 236