1 /*-------------------------------------------------------------------------
2  *
3  * resowner.h
4  *	  POSTGRES resource owner definitions.
5  *
6  * Query-lifespan resources are tracked by associating them with
7  * ResourceOwner objects.  This provides a simple mechanism for ensuring
8  * that such resources are freed at the right time.
9  * See utils/resowner/README for more info.
10  *
11  *
12  * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
13  * Portions Copyright (c) 1994, Regents of the University of California
14  *
15  * src/include/utils/resowner.h
16  *
17  *-------------------------------------------------------------------------
18  */
19 #ifndef RESOWNER_H
20 #define RESOWNER_H
21 
22 
23 /*
24  * ResourceOwner objects are an opaque data structure known only within
25  * resowner.c.
26  */
27 typedef struct ResourceOwnerData *ResourceOwner;
28 
29 
30 /*
31  * Globally known ResourceOwners
32  */
33 extern PGDLLIMPORT ResourceOwner CurrentResourceOwner;
34 extern PGDLLIMPORT ResourceOwner CurTransactionResourceOwner;
35 extern PGDLLIMPORT ResourceOwner TopTransactionResourceOwner;
36 
37 /*
38  * Resource releasing is done in three phases: pre-locks, locks, and
39  * post-locks.  The pre-lock phase must release any resources that are
40  * visible to other backends (such as pinned buffers); this ensures that
41  * when we release a lock that another backend may be waiting on, it will
42  * see us as being fully out of our transaction.  The post-lock phase
43  * should be used for backend-internal cleanup.
44  */
45 typedef enum
46 {
47 	RESOURCE_RELEASE_BEFORE_LOCKS,
48 	RESOURCE_RELEASE_LOCKS,
49 	RESOURCE_RELEASE_AFTER_LOCKS
50 } ResourceReleasePhase;
51 
52 /*
53  *	Dynamically loaded modules can get control during ResourceOwnerRelease
54  *	by providing a callback of this form.
55  */
56 typedef void (*ResourceReleaseCallback) (ResourceReleasePhase phase,
57 										 bool isCommit,
58 										 bool isTopLevel,
59 										 void *arg);
60 
61 
62 /*
63  * Functions in resowner.c
64  */
65 
66 /* generic routines */
67 extern ResourceOwner ResourceOwnerCreate(ResourceOwner parent,
68 					const char *name);
69 extern void ResourceOwnerRelease(ResourceOwner owner,
70 					 ResourceReleasePhase phase,
71 					 bool isCommit,
72 					 bool isTopLevel);
73 extern void ResourceOwnerDelete(ResourceOwner owner);
74 extern ResourceOwner ResourceOwnerGetParent(ResourceOwner owner);
75 extern void ResourceOwnerNewParent(ResourceOwner owner,
76 					   ResourceOwner newparent);
77 extern void RegisterResourceReleaseCallback(ResourceReleaseCallback callback,
78 								void *arg);
79 extern void UnregisterResourceReleaseCallback(ResourceReleaseCallback callback,
80 								  void *arg);
81 
82 #endif							/* RESOWNER_H */
83