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/*-------------------------------------------------------------------------
*
* bufmgr.h
* POSTGRES buffer manager definitions.
*
*
* Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/storage/bufmgr.h
*
*-------------------------------------------------------------------------
*/
#ifndef BUFMGR_H
#define BUFMGR_H
#include "storage/block.h"
#include "storage/buf.h"
#include "storage/bufpage.h"
#include "storage/relfilelocator.h"
#include "utils/relcache.h"
#include "utils/snapmgr.h"
typedef void *Block;
/*
* Possible arguments for GetAccessStrategy().
*
* If adding a new BufferAccessStrategyType, also add a new IOContext so
* IO statistics using this strategy are tracked.
*/
typedef enum BufferAccessStrategyType
{
BAS_NORMAL, /* Normal random access */
BAS_BULKREAD, /* Large read-only scan (hint bit updates are
* ok) */
BAS_BULKWRITE, /* Large multi-block write (e.g. COPY IN) */
BAS_VACUUM /* VACUUM */
} BufferAccessStrategyType;
/* Possible modes for ReadBufferExtended() */
typedef enum
{
RBM_NORMAL, /* Normal read */
RBM_ZERO_AND_LOCK, /* Don't read from disk, caller will
* initialize. Also locks the page. */
RBM_ZERO_AND_CLEANUP_LOCK, /* Like RBM_ZERO_AND_LOCK, but locks the page
* in "cleanup" mode */
RBM_ZERO_ON_ERROR, /* Read, but return an all-zeros page on error */
RBM_NORMAL_NO_LOG /* Don't log page as invalid during WAL
* replay; otherwise same as RBM_NORMAL */
} ReadBufferMode;
/*
* Type returned by PrefetchBuffer().
*/
typedef struct PrefetchBufferResult
{
Buffer recent_buffer; /* If valid, a hit (recheck needed!) */
bool initiated_io; /* If true, a miss resulting in async I/O */
} PrefetchBufferResult;
/*
* Flags influencing the behaviour of ExtendBufferedRel*
*/
typedef enum ExtendBufferedFlags
{
/*
* Don't acquire extension lock. This is safe only if the relation isn't
* shared, an access exclusive lock is held or if this is the startup
* process.
*/
EB_SKIP_EXTENSION_LOCK = (1 << 0),
/* Is this extension part of recovery? */
EB_PERFORMING_RECOVERY = (1 << 1),
/*
* Should the fork be created if it does not currently exist? This likely
* only ever makes sense for relation forks.
*/
EB_CREATE_FORK_IF_NEEDED = (1 << 2),
/* Should the first (possibly only) return buffer be returned locked? */
EB_LOCK_FIRST = (1 << 3),
/* Should the smgr size cache be cleared? */
EB_CLEAR_SIZE_CACHE = (1 << 4),
/* internal flags follow */
EB_LOCK_TARGET = (1 << 5),
} ExtendBufferedFlags;
/*
* Some functions identify relations either by relation or smgr +
* relpersistence. Used via the BMR_REL()/BMR_SMGR() macros below. This
* allows us to use the same function for both recovery and normal operation.
*/
typedef struct BufferManagerRelation
{
Relation rel;
struct SMgrRelationData *smgr;
char relpersistence;
} BufferManagerRelation;
#define BMR_REL(p_rel) ((BufferManagerRelation){.rel = p_rel})
#define BMR_SMGR(p_smgr, p_relpersistence) ((BufferManagerRelation){.smgr = p_smgr, .relpersistence = p_relpersistence})
/* forward declared, to avoid having to expose buf_internals.h here */
struct WritebackContext;
/* forward declared, to avoid including smgr.h here */
struct SMgrRelationData;
/* in globals.c ... this duplicates miscadmin.h */
extern PGDLLIMPORT int NBuffers;
/* in bufmgr.c */
extern PGDLLIMPORT bool zero_damaged_pages;
extern PGDLLIMPORT int bgwriter_lru_maxpages;
extern PGDLLIMPORT double bgwriter_lru_multiplier;
extern PGDLLIMPORT bool track_io_timing;
/* only applicable when prefetching is available */
#ifdef USE_PREFETCH
#define DEFAULT_EFFECTIVE_IO_CONCURRENCY 1
#define DEFAULT_MAINTENANCE_IO_CONCURRENCY 10
#else
#define DEFAULT_EFFECTIVE_IO_CONCURRENCY 0
#define DEFAULT_MAINTENANCE_IO_CONCURRENCY 0
#endif
extern PGDLLIMPORT int effective_io_concurrency;
extern PGDLLIMPORT int maintenance_io_concurrency;
extern PGDLLIMPORT int checkpoint_flush_after;
extern PGDLLIMPORT int backend_flush_after;
extern PGDLLIMPORT int bgwriter_flush_after;
/* in buf_init.c */
extern PGDLLIMPORT char *BufferBlocks;
/* in localbuf.c */
extern PGDLLIMPORT int NLocBuffer;
extern PGDLLIMPORT Block *LocalBufferBlockPointers;
extern PGDLLIMPORT int32 *LocalRefCount;
/* upper limit for effective_io_concurrency */
#define MAX_IO_CONCURRENCY 1000
/* special block number for ReadBuffer() */
#define P_NEW InvalidBlockNumber /* grow the file to get a new page */
/*
* Buffer content lock modes (mode argument for LockBuffer())
*/
#define BUFFER_LOCK_UNLOCK 0
#define BUFFER_LOCK_SHARE 1
#define BUFFER_LOCK_EXCLUSIVE 2
/*
* prototypes for functions in bufmgr.c
*/
extern PrefetchBufferResult PrefetchSharedBuffer(struct SMgrRelationData *smgr_reln,
ForkNumber forkNum,
BlockNumber blockNum);
extern PrefetchBufferResult PrefetchBuffer(Relation reln, ForkNumber forkNum,
BlockNumber blockNum);
extern bool ReadRecentBuffer(RelFileLocator rlocator, ForkNumber forkNum,
BlockNumber blockNum, Buffer recent_buffer);
extern Buffer ReadBuffer(Relation reln, BlockNumber blockNum);
extern Buffer ReadBufferExtended(Relation reln, ForkNumber forkNum,
BlockNumber blockNum, ReadBufferMode mode,
BufferAccessStrategy strategy);
extern Buffer ReadBufferWithoutRelcache(RelFileLocator rlocator,
ForkNumber forkNum, BlockNumber blockNum,
ReadBufferMode mode, BufferAccessStrategy strategy,
bool permanent);
extern void ReleaseBuffer(Buffer buffer);
extern void UnlockReleaseBuffer(Buffer buffer);
extern void MarkBufferDirty(Buffer buffer);
extern void IncrBufferRefCount(Buffer buffer);
extern void CheckBufferIsPinnedOnce(Buffer buffer);
extern Buffer ReleaseAndReadBuffer(Buffer buffer, Relation relation,
BlockNumber blockNum);
extern Buffer ExtendBufferedRel(BufferManagerRelation bmr,
ForkNumber forkNum,
BufferAccessStrategy strategy,
uint32 flags);
extern BlockNumber ExtendBufferedRelBy(BufferManagerRelation bmr,
ForkNumber fork,
BufferAccessStrategy strategy,
uint32 flags,
uint32 extend_by,
Buffer *buffers,
uint32 *extended_by);
extern Buffer ExtendBufferedRelTo(BufferManagerRelation bmr,
ForkNumber fork,
BufferAccessStrategy strategy,
uint32 flags,
BlockNumber extend_to,
ReadBufferMode mode);
extern void InitBufferPoolAccess(void);
extern void AtEOXact_Buffers(bool isCommit);
extern void PrintBufferLeakWarning(Buffer buffer);
extern void CheckPointBuffers(int flags);
extern BlockNumber BufferGetBlockNumber(Buffer buffer);
extern BlockNumber RelationGetNumberOfBlocksInFork(Relation relation,
ForkNumber forkNum);
extern void FlushOneBuffer(Buffer buffer);
extern void FlushRelationBuffers(Relation rel);
extern void FlushRelationsAllBuffers(struct SMgrRelationData **smgrs, int nrels);
extern void CreateAndCopyRelationData(RelFileLocator src_rlocator,
RelFileLocator dst_rlocator,
bool permanent);
extern void FlushDatabaseBuffers(Oid dbid);
extern void DropRelationBuffers(struct SMgrRelationData *smgr_reln,
ForkNumber *forkNum,
int nforks, BlockNumber *firstDelBlock);
extern void DropRelationsAllBuffers(struct SMgrRelationData **smgr_reln,
int nlocators);
extern void DropDatabaseBuffers(Oid dbid);
#define RelationGetNumberOfBlocks(reln) \
RelationGetNumberOfBlocksInFork(reln, MAIN_FORKNUM)
extern bool BufferIsPermanent(Buffer buffer);
extern XLogRecPtr BufferGetLSNAtomic(Buffer buffer);
#ifdef NOT_USED
extern void PrintPinnedBufs(void);
#endif
extern void BufferGetTag(Buffer buffer, RelFileLocator *rlocator,
ForkNumber *forknum, BlockNumber *blknum);
extern void MarkBufferDirtyHint(Buffer buffer, bool buffer_std);
extern void UnlockBuffers(void);
extern void LockBuffer(Buffer buffer, int mode);
extern bool ConditionalLockBuffer(Buffer buffer);
extern void LockBufferForCleanup(Buffer buffer);
extern bool ConditionalLockBufferForCleanup(Buffer buffer);
extern bool IsBufferCleanupOK(Buffer buffer);
extern bool HoldingBufferPinThatDelaysRecovery(void);
extern void AbortBufferIO(Buffer buffer);
extern bool BgBufferSync(struct WritebackContext *wb_context);
extern void TestForOldSnapshot_impl(Snapshot snapshot, Relation relation);
/* in buf_init.c */
extern void InitBufferPool(void);
extern Size BufferShmemSize(void);
/* in localbuf.c */
extern void AtProcExit_LocalBuffers(void);
/* in freelist.c */
extern BufferAccessStrategy GetAccessStrategy(BufferAccessStrategyType btype);
extern BufferAccessStrategy GetAccessStrategyWithSize(BufferAccessStrategyType btype,
int ring_size_kb);
extern int GetAccessStrategyBufferCount(BufferAccessStrategy strategy);
extern void FreeAccessStrategy(BufferAccessStrategy strategy);
/* inline functions */
/*
* Although this header file is nominally backend-only, certain frontend
* programs like pg_waldump include it. For compilers that emit static
* inline functions even when they're unused, that leads to unsatisfied
* external references; hence hide these with #ifndef FRONTEND.
*/
#ifndef FRONTEND
/*
* BufferIsValid
* True iff the given buffer number is valid (either as a shared
* or local buffer).
*
* Note: For a long time this was defined the same as BufferIsPinned,
* that is it would say False if you didn't hold a pin on the buffer.
* I believe this was bogus and served only to mask logic errors.
* Code should always know whether it has a buffer reference,
* independently of the pin state.
*
* Note: For a further long time this was not quite the inverse of the
* BufferIsInvalid() macro, in that it also did sanity checks to verify
* that the buffer number was in range. Most likely, this macro was
* originally intended only to be used in assertions, but its use has
* since expanded quite a bit, and the overhead of making those checks
* even in non-assert-enabled builds can be significant. Thus, we've
* now demoted the range checks to assertions within the macro itself.
*/
static inline bool
BufferIsValid(Buffer bufnum)
{
Assert(bufnum <= NBuffers);
Assert(bufnum >= -NLocBuffer);
return bufnum != InvalidBuffer;
}
/*
* BufferGetBlock
* Returns a reference to a disk page image associated with a buffer.
*
* Note:
* Assumes buffer is valid.
*/
static inline Block
BufferGetBlock(Buffer buffer)
{
Assert(BufferIsValid(buffer));
if (BufferIsLocal(buffer))
return LocalBufferBlockPointers[-buffer - 1];
else
return (Block) (BufferBlocks + ((Size) (buffer - 1)) * BLCKSZ);
}
/*
* BufferGetPageSize
* Returns the page size within a buffer.
*
* Notes:
* Assumes buffer is valid.
*
* The buffer can be a raw disk block and need not contain a valid
* (formatted) disk page.
*/
/* XXX should dig out of buffer descriptor */
static inline Size
BufferGetPageSize(Buffer buffer)
{
AssertMacro(BufferIsValid(buffer));
return (Size) BLCKSZ;
}
/*
* BufferGetPage
* Returns the page associated with a buffer.
*
* When this is called as part of a scan, there may be a need for a nearby
* call to TestForOldSnapshot(). See the definition of that for details.
*/
static inline Page
BufferGetPage(Buffer buffer)
{
return (Page) BufferGetBlock(buffer);
}
/*
* Check whether the given snapshot is too old to have safely read the given
* page from the given table. If so, throw a "snapshot too old" error.
*
* This test generally needs to be performed after every BufferGetPage() call
* that is executed as part of a scan. It is not needed for calls made for
* modifying the page (for example, to position to the right place to insert a
* new index tuple or for vacuuming). It may also be omitted where calls to
* lower-level functions will have already performed the test.
*
* Note that a NULL snapshot argument is allowed and causes a fast return
* without error; this is to support call sites which can be called from
* either scans or index modification areas.
*
* For best performance, keep the tests that are fastest and/or most likely to
* exclude a page from old snapshot testing near the front.
*/
static inline void
TestForOldSnapshot(Snapshot snapshot, Relation relation, Page page)
{
Assert(relation != NULL);
if (old_snapshot_threshold >= 0
&& (snapshot) != NULL
&& ((snapshot)->snapshot_type == SNAPSHOT_MVCC
|| (snapshot)->snapshot_type == SNAPSHOT_TOAST)
&& !XLogRecPtrIsInvalid((snapshot)->lsn)
&& PageGetLSN(page) > (snapshot)->lsn)
TestForOldSnapshot_impl(snapshot, relation);
}
#endif /* FRONTEND */
#endif /* BUFMGR_H */