sinval.h

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/*-------------------------------------------------------------------------
 *
 * sinval.h
 *    POSTGRES shared cache invalidation communication definitions.
 *
 *
 * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/storage/sinval.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef SINVAL_H
#define SINVAL_H
 
#include <signal.h>
 
#include "storage/relfilelocator.h"
 
/*
 * We support several types of shared-invalidation messages:
 *  * invalidate a specific tuple in a specific catcache
 *  * invalidate all catcache entries from a given system catalog
 *  * invalidate a relcache entry for a specific logical relation
 *  * invalidate all relcache entries
 *  * invalidate an smgr cache entry for a specific physical relation
 *  * invalidate the mapped-relation mapping for a given database
 *  * invalidate any saved snapshot that might be used to scan a given relation
 * More types could be added if needed.  The message type is identified by
 * the first "int8" field of the message struct.  Zero or positive means a
 * specific-catcache inval message (and also serves as the catcache ID field).
 * Negative values identify the other message types, as per codes below.
 *
 * Catcache inval events are initially driven by detecting tuple inserts,
 * updates and deletions in system catalogs (see CacheInvalidateHeapTuple).
 * An update can generate two inval events, one for the old tuple and one for
 * the new, but this is reduced to one event if the tuple's hash key doesn't
 * change.  Note that the inval events themselves don't actually say whether
 * the tuple is being inserted or deleted.  Also, since we transmit only a
 * hash key, there is a small risk of unnecessary invalidations due to chance
 * matches of hash keys.
 *
 * Note that some system catalogs have multiple caches on them (with different
 * indexes).  On detecting a tuple invalidation in such a catalog, separate
 * catcache inval messages must be generated for each of its caches, since
 * the hash keys will generally be different.
 *
 * Catcache, relcache, and snapshot invalidations are transactional, and so
 * are sent to other backends upon commit.  Internally to the generating
 * backend, they are also processed at CommandCounterIncrement so that later
 * commands in the same transaction see the new state.  The generating backend
 * also has to process them at abort, to flush out any cache state it's loaded
 * from no-longer-valid entries.
 *
 * smgr and relation mapping invalidations are non-transactional: they are
 * sent immediately when the underlying file change is made.
 */
 
typedef struct
{
    int8        id;             /* cache ID --- must be first */
    Oid         dbId;           /* database ID, or 0 if a shared relation */
    uint32      hashValue;      /* hash value of key for this catcache */
} SharedInvalCatcacheMsg;
 
#define SHAREDINVALCATALOG_ID   (-1)
 
typedef struct
{
    int8        id;             /* type field --- must be first */
    Oid         dbId;           /* database ID, or 0 if a shared catalog */
    Oid         catId;          /* ID of catalog whose contents are invalid */
} SharedInvalCatalogMsg;
 
#define SHAREDINVALRELCACHE_ID  (-2)
 
typedef struct
{
    int8        id;             /* type field --- must be first */
    Oid         dbId;           /* database ID, or 0 if a shared relation */
    Oid         relId;          /* relation ID, or 0 if whole relcache */
} SharedInvalRelcacheMsg;
 
#define SHAREDINVALSMGR_ID      (-3)
 
typedef struct
{
    /* note: field layout chosen to pack into 16 bytes */
    int8        id;             /* type field --- must be first */
    int8        backend_hi;     /* high bits of backend procno, if temprel */
    uint16      backend_lo;     /* low bits of backend procno, if temprel */
    RelFileLocator rlocator;    /* spcOid, dbOid, relNumber */
} SharedInvalSmgrMsg;
 
#define SHAREDINVALRELMAP_ID    (-4)
 
typedef struct
{
    int8        id;             /* type field --- must be first */
    Oid         dbId;           /* database ID, or 0 for shared catalogs */
} SharedInvalRelmapMsg;
 
#define SHAREDINVALSNAPSHOT_ID  (-5)
 
typedef struct
{
    int8        id;             /* type field --- must be first */
    Oid         dbId;           /* database ID, or 0 if a shared relation */
    Oid         relId;          /* relation ID */
} SharedInvalSnapshotMsg;
 
typedef union
{
    int8        id;             /* type field --- must be first */
    SharedInvalCatcacheMsg cc;
    SharedInvalCatalogMsg cat;
    SharedInvalRelcacheMsg rc;
    SharedInvalSmgrMsg sm;
    SharedInvalRelmapMsg rm;
    SharedInvalSnapshotMsg sn;
} SharedInvalidationMessage;
 
 
/* Counter of messages processed; don't worry about overflow. */
extern PGDLLIMPORT uint64 SharedInvalidMessageCounter;
 
extern PGDLLIMPORT volatile sig_atomic_t catchupInterruptPending;
 
extern void SendSharedInvalidMessages(const SharedInvalidationMessage *msgs,
                                      int n);
extern void ReceiveSharedInvalidMessages(void (*invalFunction) (SharedInvalidationMessage *msg),
                                         void (*resetFunction) (void));
 
/* signal handler for catchup events (PROCSIG_CATCHUP_INTERRUPT) */
extern void HandleCatchupInterrupt(void);
 
/*
 * enable/disable processing of catchup events directly from signal handler.
 * The enable routine first performs processing of any catchup events that
 * have occurred since the last disable.
 */
extern void ProcessCatchupInterrupt(void);
 
extern int  xactGetCommittedInvalidationMessages(SharedInvalidationMessage **msgs,
                                                 bool *RelcacheInitFileInval);
extern void ProcessCommittedInvalidationMessages(SharedInvalidationMessage *msgs,
                                                 int nmsgs, bool RelcacheInitFileInval,
                                                 Oid dbid, Oid tsid);
 
extern void LocalExecuteInvalidationMessage(SharedInvalidationMessage *msg);
 
#endif                          /* SINVAL_H */