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/*-------------------------------------------------------------------------
*
* plancache.h
* Plan cache definitions.
*
* See plancache.c for comments.
*
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/utils/plancache.h,v 1.16 2009/11/04 22:26:07 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#ifndef PLANCACHE_H
#define PLANCACHE_H
#include "access/tupdesc.h"
#include "nodes/params.h"
/*
* 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.
*
* 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.
*
* 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.
*
* Note: the string referenced by commandTag is not subsidiary storage;
* it is assumed to be a compile-time-constant string. As with portals,
* commandTag shall be NULL if and only if the original query string (before
* rewriting) was an empty string.
*/
typedef struct CachedPlanSource
{
Node *raw_parse_tree; /* output of raw_parser() */
char *query_string; /* text of query (as of 8.4, never NULL) */
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 */
} 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.
* 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 */
TransactionId saved_xmin; /* if valid, replan when TransactionXmin
* changes from this value */
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 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,
ParserSetupHook parserSetup,
void *parserSetupArg);
extern void DropCachedPlan(CachedPlanSource *plansource);
extern CachedPlan *RevalidateCachedPlan(CachedPlanSource *plansource,
bool useResOwner);
extern void ReleaseCachedPlan(CachedPlan *plan, bool useResOwner);
extern bool CachedPlanIsValid(CachedPlanSource *plansource);
extern TupleDesc PlanCacheComputeResultDesc(List *stmt_list);
extern void ResetPlanCache(void);
#endif /* PLANCACHE_H */
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