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/*-------------------------------------------------------------------------
*
* fsm_internals.h
* internal functions for free space map
*
*
* Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/storage/fsm_internals.h
*
*-------------------------------------------------------------------------
*/
#ifndef FSM_INTERNALS_H
#define FSM_INTERNALS_H
#include "storage/buf.h"
#include "storage/bufpage.h"
/*
* Structure of a FSM page. See src/backend/storage/freespace/README for
* details.
*/
typedef struct
{
/*
* fsm_search_avail() tries to spread the load of multiple backends by
* returning different pages to different backends in a round-robin
* fashion. fp_next_slot points to the next slot to be returned (assuming
* there's enough space on it for the request). It's defined as an int,
* because it's updated without an exclusive lock. uint16 would be more
* appropriate, but int is more likely to be atomically
* fetchable/storable.
*/
int fp_next_slot;
/*
* fp_nodes contains the binary tree, stored in array. The first
* NonLeafNodesPerPage elements are upper nodes, and the following
* LeafNodesPerPage elements are leaf nodes. Unused nodes are zero.
*/
uint8 fp_nodes[FLEXIBLE_ARRAY_MEMBER];
} FSMPageData;
typedef FSMPageData *FSMPage;
/*
* Number of non-leaf and leaf nodes, and nodes in total, on an FSM page.
* These definitions are internal to fsmpage.c.
*/
#define NodesPerPage (BLCKSZ - MAXALIGN(SizeOfPageHeaderData) - \
offsetof(FSMPageData, fp_nodes))
#define NonLeafNodesPerPage (BLCKSZ / 2 - 1)
#define LeafNodesPerPage (NodesPerPage - NonLeafNodesPerPage)
/*
* Number of FSM "slots" on a FSM page. This is what should be used
* outside fsmpage.c.
*/
#define SlotsPerFSMPage LeafNodesPerPage
/* Prototypes for functions in fsmpage.c */
extern int fsm_search_avail(Buffer buf, uint8 min_cat, bool advancenext,
bool exclusive_lock_held);
extern uint8 fsm_get_avail(Page page, int slot);
extern uint8 fsm_get_max_avail(Page page);
extern bool fsm_set_avail(Page page, int slot, uint8 value);
extern bool fsm_truncate_avail(Page page, int nslots);
extern bool fsm_rebuild_page(Page page);
#endif /* FSM_INTERNALS_H */
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