1/*-------------------------------------------------------------------------
2 *
3 * fsm_internal.h
4 * internal functions for free space map
5 *
6 *
7 * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
8 * Portions Copyright (c) 1994, Regents of the University of California
9 *
10 * src/include/storage/fsm_internals.h
11 *
12 *-------------------------------------------------------------------------
13 */
14#ifndef FSM_INTERNALS_H
15#define FSM_INTERNALS_H
16
17#include "storage/buf.h"
18#include "storage/bufpage.h"
19
20/*
21 * Structure of a FSM page. See src/backend/storage/freespace/README for
22 * details.
23 */
24typedef struct
25{
26 /*
27 * fsm_search_avail() tries to spread the load of multiple backends by
28 * returning different pages to different backends in a round-robin
29 * fashion. fp_next_slot points to the next slot to be returned (assuming
30 * there's enough space on it for the request). It's defined as an int,
31 * because it's updated without an exclusive lock. uint16 would be more
32 * appropriate, but int is more likely to be atomically
33 * fetchable/storable.
34 */
35 int fp_next_slot;
36
37 /*
38 * fp_nodes contains the binary tree, stored in array. The first
39 * NonLeafNodesPerPage elements are upper nodes, and the following
40 * LeafNodesPerPage elements are leaf nodes. Unused nodes are zero.
41 */
42 uint8 fp_nodes[FLEXIBLE_ARRAY_MEMBER];
43} FSMPageData;
44
45typedef FSMPageData *FSMPage;
46
47/*
48 * Number of non-leaf and leaf nodes, and nodes in total, on an FSM page.
49 * These definitions are internal to fsmpage.c.
50 */
51#define NodesPerPage (BLCKSZ - MAXALIGN(SizeOfPageHeaderData) - \
52 offsetof(FSMPageData, fp_nodes))
53
54#define NonLeafNodesPerPage (BLCKSZ / 2 - 1)
55#define LeafNodesPerPage (NodesPerPage - NonLeafNodesPerPage)
56
57/*
58 * Number of FSM "slots" on a FSM page. This is what should be used
59 * outside fsmpage.c.
60 */
61#define SlotsPerFSMPage LeafNodesPerPage
62
63/* Prototypes for functions in fsmpage.c */
64extern int fsm_search_avail(Buffer buf, uint8 min_cat, bool advancenext,
65 bool exclusive_lock_held);
66extern uint8 fsm_get_avail(Page page, int slot);
67extern uint8 fsm_get_max_avail(Page page);
68extern bool fsm_set_avail(Page page, int slot, uint8 value);
69extern bool fsm_truncate_avail(Page page, int nslots);
70extern bool fsm_rebuild_page(Page page);
71
72#endif /* FSM_INTERNALS_H */
73