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/*-------------------------------------------------------------------------
*
* sinval.h
* POSTGRES shared cache invalidation communication definitions.
*
*
* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: sinval.h,v 1.22 2001/09/29 04:02:27 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#ifndef SINVAL_H
#define SINVAL_H
#include "storage/backendid.h"
#include "storage/itemptr.h"
/*
* We currently support two types of shared-invalidation messages: one that
* invalidates an entry in a catcache, and one that invalidates a relcache
* entry. More types could be added if needed. The message type is
* identified by the first "int16" field of the message struct. Zero or
* positive means a catcache inval message (and also serves as the catcache
* ID field). -1 means a relcache inval message. Other negative values
* are available to identify other inval message types.
*
* Shared-inval events are initially driven by detecting tuple inserts,
* updates and deletions in system catalogs (see RelationInvalidateHeapTuple
* and RelationMark4RollbackHeapTuple). Note that some system catalogs have
* multiple caches on them (with different indexes). On detecting a tuple
* invalidation in such a catalog, a separate catcache inval message must be
* generated for each of its caches. The catcache inval message carries the
* hash index for the target tuple, so that the catcache only needs to search
* one hash chain not all its chains. Of course this assumes that all the
* backends are using identical hashing code, but that should be OK.
*/
typedef struct
{
int16 id; /* cache ID --- must be first */
uint16 hashIndex; /* hashchain index within this catcache */
Oid dbId; /* database ID, or 0 if a shared relation */
ItemPointerData tuplePtr; /* tuple identifier in cached relation */
} SharedInvalCatcacheMsg;
#define SHAREDINVALRELCACHE_ID (-1)
typedef struct
{
int16 id; /* type field --- must be first */
Oid dbId; /* database ID, or 0 if a shared relation */
Oid relId; /* relation ID */
} SharedInvalRelcacheMsg;
typedef union
{
int16 id; /* type field --- must be first */
SharedInvalCatcacheMsg cc;
SharedInvalRelcacheMsg rc;
} SharedInvalidationMessage;
extern int SInvalShmemSize(int maxBackends);
extern void CreateSharedInvalidationState(int maxBackends);
extern void InitBackendSharedInvalidationState(void);
extern void SendSharedInvalidMessage(SharedInvalidationMessage *msg);
extern void ReceiveSharedInvalidMessages(
void (*invalFunction) (SharedInvalidationMessage *msg),
void (*resetFunction) (void));
extern bool DatabaseHasActiveBackends(Oid databaseId, bool ignoreMyself);
extern bool TransactionIdIsInProgress(TransactionId xid);
extern TransactionId GetOldestXmin(bool allDbs);
extern int CountActiveBackends(void);
/* Use "struct PROC", not PROC, to avoid including proc.h here */
extern struct PROC *BackendIdGetProc(BackendId procId);
#endif /* SINVAL_H */
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