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87bd956385
the relcache, and so the notion of 'blind write' is gone. This should improve efficiency in bgwriter and background checkpoint processes. Internal restructuring in md.c to remove the not-very-useful array of MdfdVec objects --- might as well just use pointers. Also remove the long-dead 'persistent main memory' storage manager (mm.c), since it seems quite unlikely to ever get resurrected.
109 lines
4.4 KiB
C
109 lines
4.4 KiB
C
/*-------------------------------------------------------------------------
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*
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* sinval.h
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* POSTGRES shared cache invalidation communication definitions.
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*
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*
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* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/storage/sinval.h,v 1.33 2004/02/10 01:55:26 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef SINVAL_H
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#define SINVAL_H
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#include "storage/backendid.h"
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#include "storage/itemptr.h"
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#include "storage/relfilenode.h"
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/*
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* We currently support two types of shared-invalidation messages: one that
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* invalidates an entry in a catcache, and one that invalidates a relcache
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* entry. More types could be added if needed. The message type is
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* identified by the first "int16" field of the message struct. Zero or
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* positive means a catcache inval message (and also serves as the catcache
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* ID field). -1 means a relcache inval message. Other negative values
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* are available to identify other inval message types.
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*
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* Relcache invalidation messages usually also cause invalidation of entries
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* in the smgr's relation cache. This means they must carry both logical
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* and physical relation ID info (ie, both dbOID/relOID and RelFileNode).
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* In some cases RelFileNode information is not available so the sender fills
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* those fields with zeroes --- this is okay so long as no smgr cache flush
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* is required.
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*
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* Shared-inval events are initially driven by detecting tuple inserts,
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* updates and deletions in system catalogs (see CacheInvalidateHeapTuple).
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* An update generates two inval events, one for the old tuple and one for
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* the new --- this is needed to get rid of both positive entries for the
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* old tuple, and negative cache entries associated with the new tuple's
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* cache key. (This could perhaps be optimized down to one event when the
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* cache key is not changing, but for now we don't bother to try.) Note that
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* the inval events themselves don't actually say whether the tuple is being
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* inserted or deleted.
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*
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* Note that some system catalogs have multiple caches on them (with different
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* indexes). On detecting a tuple invalidation in such a catalog, separate
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* catcache inval messages must be generated for each of its caches. The
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* catcache inval messages carry the hash value for the target tuple, so
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* that the catcache only needs to search one hash chain not all its chains,
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* and so that negative cache entries can be recognized with good accuracy.
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* (Of course this assumes that all the backends are using identical hashing
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* code, but that should be OK.)
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*/
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typedef struct
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{
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/* note: field layout chosen with an eye to alignment concerns */
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int16 id; /* cache ID --- must be first */
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ItemPointerData tuplePtr; /* tuple identifier in cached relation */
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Oid dbId; /* database ID, or 0 if a shared relation */
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uint32 hashValue; /* hash value of key for this catcache */
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} SharedInvalCatcacheMsg;
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#define SHAREDINVALRELCACHE_ID (-1)
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typedef struct
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{
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int16 id; /* type field --- must be first */
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Oid dbId; /* database ID, or 0 if a shared relation */
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Oid relId; /* relation ID */
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RelFileNode physId; /* physical file ID */
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/*
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* Note: it is likely that RelFileNode will someday be changed to
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* include database ID. In that case the dbId field will be redundant
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* and should be removed to save space.
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*/
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} SharedInvalRelcacheMsg;
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typedef union
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{
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int16 id; /* type field --- must be first */
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SharedInvalCatcacheMsg cc;
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SharedInvalRelcacheMsg rc;
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} SharedInvalidationMessage;
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extern int SInvalShmemSize(int maxBackends);
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extern void CreateSharedInvalidationState(int maxBackends);
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extern void InitBackendSharedInvalidationState(void);
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extern void SendSharedInvalidMessage(SharedInvalidationMessage *msg);
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extern void ReceiveSharedInvalidMessages(
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void (*invalFunction) (SharedInvalidationMessage *msg),
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void (*resetFunction) (void));
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extern bool DatabaseHasActiveBackends(Oid databaseId, bool ignoreMyself);
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extern bool TransactionIdIsInProgress(TransactionId xid);
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extern TransactionId GetOldestXmin(bool allDbs);
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extern int CountActiveBackends(void);
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/* Use "struct PGPROC", not PGPROC, to avoid including proc.h here */
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extern struct PGPROC *BackendIdGetProc(BackendId procId);
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extern int CountEmptyBackendSlots(void);
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#endif /* SINVAL_H */
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