280 lines
9.1 KiB
C
280 lines
9.1 KiB
C
/*-------------------------------------------------------------------------
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*
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* bufmgr.h
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* POSTGRES buffer manager definitions.
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*
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*
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* Portions Copyright (c) 1996-2019, 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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* src/include/storage/bufmgr.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef BUFMGR_H
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#define BUFMGR_H
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#include "storage/block.h"
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#include "storage/buf.h"
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#include "storage/bufpage.h"
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#include "storage/relfilenode.h"
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#include "utils/relcache.h"
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#include "utils/snapmgr.h"
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typedef void *Block;
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/* Possible arguments for GetAccessStrategy() */
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typedef enum BufferAccessStrategyType
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{
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BAS_NORMAL, /* Normal random access */
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BAS_BULKREAD, /* Large read-only scan (hint bit updates are
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* ok) */
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BAS_BULKWRITE, /* Large multi-block write (e.g. COPY IN) */
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BAS_VACUUM /* VACUUM */
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} BufferAccessStrategyType;
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/* Possible modes for ReadBufferExtended() */
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typedef enum
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{
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RBM_NORMAL, /* Normal read */
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RBM_ZERO_AND_LOCK, /* Don't read from disk, caller will
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* initialize. Also locks the page. */
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RBM_ZERO_AND_CLEANUP_LOCK, /* Like RBM_ZERO_AND_LOCK, but locks the page
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* in "cleanup" mode */
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RBM_ZERO_ON_ERROR, /* Read, but return an all-zeros page on error */
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RBM_NORMAL_NO_LOG /* Don't log page as invalid during WAL
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* replay; otherwise same as RBM_NORMAL */
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} ReadBufferMode;
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/* forward declared, to avoid having to expose buf_internals.h here */
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struct WritebackContext;
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/* in globals.c ... this duplicates miscadmin.h */
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extern PGDLLIMPORT int NBuffers;
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/* in bufmgr.c */
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extern bool zero_damaged_pages;
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extern int bgwriter_lru_maxpages;
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extern double bgwriter_lru_multiplier;
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extern bool track_io_timing;
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extern int target_prefetch_pages;
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extern int checkpoint_flush_after;
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extern int backend_flush_after;
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extern int bgwriter_flush_after;
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/* in buf_init.c */
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extern PGDLLIMPORT char *BufferBlocks;
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/* in guc.c */
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extern int effective_io_concurrency;
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/* in localbuf.c */
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extern PGDLLIMPORT int NLocBuffer;
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extern PGDLLIMPORT Block *LocalBufferBlockPointers;
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extern PGDLLIMPORT int32 *LocalRefCount;
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/* upper limit for effective_io_concurrency */
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#define MAX_IO_CONCURRENCY 1000
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/* special block number for ReadBuffer() */
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#define P_NEW InvalidBlockNumber /* grow the file to get a new page */
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/*
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* Buffer content lock modes (mode argument for LockBuffer())
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*/
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#define BUFFER_LOCK_UNLOCK 0
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#define BUFFER_LOCK_SHARE 1
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#define BUFFER_LOCK_EXCLUSIVE 2
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/*
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* These routines are beaten on quite heavily, hence the macroization.
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*/
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/*
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* BufferIsValid
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* True iff the given buffer number is valid (either as a shared
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* or local buffer).
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*
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* Note: For a long time this was defined the same as BufferIsPinned,
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* that is it would say False if you didn't hold a pin on the buffer.
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* I believe this was bogus and served only to mask logic errors.
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* Code should always know whether it has a buffer reference,
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* independently of the pin state.
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*
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* Note: For a further long time this was not quite the inverse of the
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* BufferIsInvalid() macro, in that it also did sanity checks to verify
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* that the buffer number was in range. Most likely, this macro was
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* originally intended only to be used in assertions, but its use has
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* since expanded quite a bit, and the overhead of making those checks
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* even in non-assert-enabled builds can be significant. Thus, we've
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* now demoted the range checks to assertions within the macro itself.
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*/
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#define BufferIsValid(bufnum) \
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( \
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AssertMacro((bufnum) <= NBuffers && (bufnum) >= -NLocBuffer), \
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(bufnum) != InvalidBuffer \
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)
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/*
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* BufferGetBlock
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* Returns a reference to a disk page image associated with a buffer.
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*
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* Note:
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* Assumes buffer is valid.
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*/
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#define BufferGetBlock(buffer) \
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( \
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AssertMacro(BufferIsValid(buffer)), \
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BufferIsLocal(buffer) ? \
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LocalBufferBlockPointers[-(buffer) - 1] \
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: \
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(Block) (BufferBlocks + ((Size) ((buffer) - 1)) * BLCKSZ) \
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)
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/*
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* BufferGetPageSize
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* Returns the page size within a buffer.
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*
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* Notes:
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* Assumes buffer is valid.
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*
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* The buffer can be a raw disk block and need not contain a valid
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* (formatted) disk page.
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*/
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/* XXX should dig out of buffer descriptor */
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#define BufferGetPageSize(buffer) \
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( \
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AssertMacro(BufferIsValid(buffer)), \
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(Size)BLCKSZ \
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)
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/*
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* BufferGetPage
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* Returns the page associated with a buffer.
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*
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* When this is called as part of a scan, there may be a need for a nearby
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* call to TestForOldSnapshot(). See the definition of that for details.
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*/
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#define BufferGetPage(buffer) ((Page)BufferGetBlock(buffer))
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/*
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* prototypes for functions in bufmgr.c
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*/
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extern bool ComputeIoConcurrency(int io_concurrency, double *target);
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extern void PrefetchBuffer(Relation reln, ForkNumber forkNum,
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BlockNumber blockNum);
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extern Buffer ReadBuffer(Relation reln, BlockNumber blockNum);
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extern Buffer ReadBufferExtended(Relation reln, ForkNumber forkNum,
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BlockNumber blockNum, ReadBufferMode mode,
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BufferAccessStrategy strategy);
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extern Buffer ReadBufferWithoutRelcache(RelFileNode rnode,
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ForkNumber forkNum, BlockNumber blockNum,
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ReadBufferMode mode, BufferAccessStrategy strategy);
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extern void ReleaseBuffer(Buffer buffer);
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extern void UnlockReleaseBuffer(Buffer buffer);
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extern void MarkBufferDirty(Buffer buffer);
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extern void IncrBufferRefCount(Buffer buffer);
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extern Buffer ReleaseAndReadBuffer(Buffer buffer, Relation relation,
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BlockNumber blockNum);
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extern void InitBufferPool(void);
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extern void InitBufferPoolAccess(void);
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extern void InitBufferPoolBackend(void);
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extern void AtEOXact_Buffers(bool isCommit);
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extern void PrintBufferLeakWarning(Buffer buffer);
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extern void CheckPointBuffers(int flags);
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extern BlockNumber BufferGetBlockNumber(Buffer buffer);
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extern BlockNumber RelationGetNumberOfBlocksInFork(Relation relation,
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ForkNumber forkNum);
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extern void FlushOneBuffer(Buffer buffer);
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extern void FlushRelationBuffers(Relation rel);
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extern void FlushDatabaseBuffers(Oid dbid);
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extern void DropRelFileNodeBuffers(RelFileNodeBackend rnode, ForkNumber *forkNum,
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int nforks, BlockNumber *firstDelBlock);
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extern void DropRelFileNodesAllBuffers(RelFileNodeBackend *rnodes, int nnodes);
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extern void DropDatabaseBuffers(Oid dbid);
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#define RelationGetNumberOfBlocks(reln) \
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RelationGetNumberOfBlocksInFork(reln, MAIN_FORKNUM)
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extern bool BufferIsPermanent(Buffer buffer);
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extern XLogRecPtr BufferGetLSNAtomic(Buffer buffer);
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#ifdef NOT_USED
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extern void PrintPinnedBufs(void);
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#endif
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extern Size BufferShmemSize(void);
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extern void BufferGetTag(Buffer buffer, RelFileNode *rnode,
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ForkNumber *forknum, BlockNumber *blknum);
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extern void MarkBufferDirtyHint(Buffer buffer, bool buffer_std);
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extern void UnlockBuffers(void);
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extern void LockBuffer(Buffer buffer, int mode);
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extern bool ConditionalLockBuffer(Buffer buffer);
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extern void LockBufferForCleanup(Buffer buffer);
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extern bool ConditionalLockBufferForCleanup(Buffer buffer);
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extern bool IsBufferCleanupOK(Buffer buffer);
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extern bool HoldingBufferPinThatDelaysRecovery(void);
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extern void AbortBufferIO(void);
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extern void BufmgrCommit(void);
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extern bool BgBufferSync(struct WritebackContext *wb_context);
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extern void AtProcExit_LocalBuffers(void);
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extern void TestForOldSnapshot_impl(Snapshot snapshot, Relation relation);
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/* in freelist.c */
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extern BufferAccessStrategy GetAccessStrategy(BufferAccessStrategyType btype);
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extern void FreeAccessStrategy(BufferAccessStrategy strategy);
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/* inline functions */
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/*
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* Although this header file is nominally backend-only, certain frontend
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* programs like pg_waldump include it. For compilers that emit static
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* inline functions even when they're unused, that leads to unsatisfied
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* external references; hence hide these with #ifndef FRONTEND.
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*/
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#ifndef FRONTEND
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/*
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* Check whether the given snapshot is too old to have safely read the given
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* page from the given table. If so, throw a "snapshot too old" error.
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*
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* This test generally needs to be performed after every BufferGetPage() call
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* that is executed as part of a scan. It is not needed for calls made for
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* modifying the page (for example, to position to the right place to insert a
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* new index tuple or for vacuuming). It may also be omitted where calls to
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* lower-level functions will have already performed the test.
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*
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* Note that a NULL snapshot argument is allowed and causes a fast return
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* without error; this is to support call sites which can be called from
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* either scans or index modification areas.
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*
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* For best performance, keep the tests that are fastest and/or most likely to
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* exclude a page from old snapshot testing near the front.
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*/
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static inline void
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TestForOldSnapshot(Snapshot snapshot, Relation relation, Page page)
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{
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Assert(relation != NULL);
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if (old_snapshot_threshold >= 0
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&& (snapshot) != NULL
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&& ((snapshot)->snapshot_type == SNAPSHOT_MVCC
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|| (snapshot)->snapshot_type == SNAPSHOT_TOAST)
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&& !XLogRecPtrIsInvalid((snapshot)->lsn)
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&& PageGetLSN(page) > (snapshot)->lsn)
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TestForOldSnapshot_impl(snapshot, relation);
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}
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#endif /* FRONTEND */
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#endif /* BUFMGR_H */
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