resowner.h

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/*-------------------------------------------------------------------------
 *
 * resowner.h
 *    POSTGRES resource owner definitions.
 *
 * Query-lifespan resources are tracked by associating them with
 * ResourceOwner objects.  This provides a simple mechanism for ensuring
 * that such resources are freed at the right time.
 * See utils/resowner/README for more info.
 *
 *
 * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/utils/resowner.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef RESOWNER_H
#define RESOWNER_H


/*
 * ResourceOwner objects are an opaque data structure known only within
 * resowner.c.
 */
typedef struct ResourceOwnerData *ResourceOwner;


/*
 * Globally known ResourceOwners
 */
extern PGDLLIMPORT ResourceOwner CurrentResourceOwner;
extern PGDLLIMPORT ResourceOwner CurTransactionResourceOwner;
extern PGDLLIMPORT ResourceOwner TopTransactionResourceOwner;

/*
 * Resource releasing is done in three phases: pre-locks, locks, and
 * post-locks.  The pre-lock phase must release any resources that are
 * visible to other backends (such as pinned buffers); this ensures that
 * when we release a lock that another backend may be waiting on, it will
 * see us as being fully out of our transaction.  The post-lock phase
 * should be used for backend-internal cleanup.
 */
typedef enum
{
    RESOURCE_RELEASE_BEFORE_LOCKS,
    RESOURCE_RELEASE_LOCKS,
    RESOURCE_RELEASE_AFTER_LOCKS
} ResourceReleasePhase;

/*
 *  Dynamically loaded modules can get control during ResourceOwnerRelease
 *  by providing a callback of this form.
 */
typedef void (*ResourceReleaseCallback) (ResourceReleasePhase phase,
                                                     bool isCommit,
                                                     bool isTopLevel,
                                                     void *arg);


/*
 * Functions in resowner.c
 */

/* generic routines */
extern ResourceOwner ResourceOwnerCreate(ResourceOwner parent,
                    const char *name);
extern void ResourceOwnerRelease(ResourceOwner owner,
                     ResourceReleasePhase phase,
                     bool isCommit,
                     bool isTopLevel);
extern void ResourceOwnerDelete(ResourceOwner owner);
extern ResourceOwner ResourceOwnerGetParent(ResourceOwner owner);
extern void ResourceOwnerNewParent(ResourceOwner owner,
                       ResourceOwner newparent);
extern void RegisterResourceReleaseCallback(ResourceReleaseCallback callback,
                                void *arg);
extern void UnregisterResourceReleaseCallback(ResourceReleaseCallback callback,
                                  void *arg);

#endif   /* RESOWNER_H */