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/*-------------------------------------------------------------------------
* slot.h
* Replication slot management.
*
* Copyright (c) 2012-2014, PostgreSQL Global Development Group
*
*-------------------------------------------------------------------------
*/
#ifndef SLOT_H
#define SLOT_H
#include "fmgr.h"
#include "access/xlog.h"
#include "access/xlogreader.h"
#include "storage/lwlock.h"
#include "storage/shmem.h"
#include "storage/spin.h"
typedef struct ReplicationSlotPersistentData
{
/* The slot's identifier */
NameData name;
/* database the slot is active on */
Oid database;
/*
* xmin horizon for data
*
* NB: This may represent a value that hasn't been written to disk yet;
* see notes for effective_xmin, below.
*/
TransactionId xmin;
/* oldest LSN that might be required by this replication slot */
XLogRecPtr restart_lsn;
} ReplicationSlotPersistentData;
/*
* Shared memory state of a single replication slot.
*/
typedef struct ReplicationSlot
{
/* lock, on same cacheline as effective_xmin */
slock_t mutex;
/* is this slot defined */
bool in_use;
/* is somebody streaming out changes for this slot */
bool active;
/* any outstanding modifications? */
bool just_dirtied;
bool dirty;
/*
* For logical decoding, it's extremely important that we never remove any
* data that's still needed for decoding purposes, even after a crash;
* otherwise, decoding will produce wrong answers. Ordinary streaming
* replication also needs to prevent old row versions from being removed
* too soon, but the worst consequence we might encounter there is unwanted
* query cancellations on the standby. Thus, for logical decoding,
* this value represents the latest xmin that has actually been
* written to disk, whereas for streaming replication, it's just the
* same as the persistent value (data.xmin).
*/
TransactionId effective_xmin;
/* data surviving shutdowns and crashes */
ReplicationSlotPersistentData data;
/* is somebody performing io on this slot? */
LWLock *io_in_progress_lock;
} ReplicationSlot;
/*
* Shared memory control area for all of replication slots.
*/
typedef struct ReplicationSlotCtlData
{
ReplicationSlot replication_slots[1];
} ReplicationSlotCtlData;
/*
* Pointers to shared memory
*/
extern ReplicationSlotCtlData *ReplicationSlotCtl;
extern ReplicationSlot *MyReplicationSlot;
/* GUCs */
extern PGDLLIMPORT int max_replication_slots;
/* shmem initialization functions */
extern Size ReplicationSlotsShmemSize(void);
extern void ReplicationSlotsShmemInit(void);
/* management of individual slots */
extern void ReplicationSlotCreate(const char *name, bool db_specific);
extern void ReplicationSlotDrop(const char *name);
extern void ReplicationSlotAcquire(const char *name);
extern void ReplicationSlotRelease(void);
extern void ReplicationSlotSave(void);
extern void ReplicationSlotMarkDirty(void);
/* misc stuff */
extern bool ReplicationSlotValidateName(const char *name, int elevel);
extern void ReplicationSlotsComputeRequiredXmin(void);
extern void ReplicationSlotsComputeRequiredLSN(void);
extern void StartupReplicationSlots(XLogRecPtr checkPointRedo);
extern void CheckPointReplicationSlots(void);
extern void CheckSlotRequirements(void);
extern void ReplicationSlotAtProcExit(void);
/* SQL callable functions */
extern Datum pg_get_replication_slots(PG_FUNCTION_ARGS);
#endif /* SLOT_H */
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