src/include/storage/bufmgr.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * bufmgr.h
   4  *        POSTGRES buffer manager definitions.
   5  *
   6  *
   7  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
   8  * Portions Copyright (c) 1994, Regents of the University of California
   9  *
  10  * $PostgreSQL$
  11  *
  12  *-------------------------------------------------------------------------
  13  */
  14 #ifndef BUFMGR_H
  15 #define BUFMGR_H
  16
  17 #include "storage/block.h"
  18 #include "storage/buf.h"
  19 #include "storage/bufpage.h"
  20 #include "storage/relfilenode.h"
  21 #include "utils/relcache.h"
  22
  23 typedef void *Block;
  24
  25 /* Possible arguments for GetAccessStrategy() */
  26 typedef enum BufferAccessStrategyType
  27 {
  28         BAS_NORMAL,                                     /* Normal random access */
  29         BAS_BULKREAD,                           /* Large read-only scan (hint bit updates are
  30                                                                  * ok) */
  31         BAS_VACUUM                                      /* VACUUM */
  32 } BufferAccessStrategyType;
  33
  34 /* Possible modes for ReadBufferExtended() */
  35 typedef enum
  36 {
  37         RBM_NORMAL,                     /* Normal read */
  38         RBM_ZERO,                       /* Don't read from disk, caller will initialize */
  39         RBM_ZERO_ON_ERROR       /* Read, but return an all-zeros page on error */
  40 } ReadBufferMode;
  41
  42 /* in globals.c ... this duplicates miscadmin.h */
  43 extern PGDLLIMPORT int NBuffers;
  44
  45 /* in bufmgr.c */
  46 extern bool zero_damaged_pages;
  47 extern int      bgwriter_lru_maxpages;
  48 extern double bgwriter_lru_multiplier;
  49
  50 /* in buf_init.c */
  51 extern PGDLLIMPORT char *BufferBlocks;
  52 extern PGDLLIMPORT int32 *PrivateRefCount;
  53
  54 /* in localbuf.c */
  55 extern PGDLLIMPORT int NLocBuffer;
  56 extern PGDLLIMPORT Block *LocalBufferBlockPointers;
  57 extern PGDLLIMPORT int32 *LocalRefCount;
  58
  59 /* special block number for ReadBuffer() */
  60 #define P_NEW   InvalidBlockNumber              /* grow the file to get a new page */
  61
  62 /*
  63  * Buffer content lock modes (mode argument for LockBuffer())
  64  */
  65 #define BUFFER_LOCK_UNLOCK              0
  66 #define BUFFER_LOCK_SHARE               1
  67 #define BUFFER_LOCK_EXCLUSIVE   2
  68
  69 /*
  70  * These routines are beaten on quite heavily, hence the macroization.
  71  */
  72
  73 /*
  74  * BufferIsValid
  75  *              True iff the given buffer number is valid (either as a shared
  76  *              or local buffer).
  77  *
  78  * This is not quite the inverse of the BufferIsInvalid() macro, since this
  79  * adds sanity rangechecks on the buffer number.
  80  *
  81  * Note: For a long time this was defined the same as BufferIsPinned,
  82  * that is it would say False if you didn't hold a pin on the buffer.
  83  * I believe this was bogus and served only to mask logic errors.
  84  * Code should always know whether it has a buffer reference,
  85  * independently of the pin state.
  86  */
  87 #define BufferIsValid(bufnum) \
  88 ( \
  89         (bufnum) != InvalidBuffer && \
  90         (bufnum) >= -NLocBuffer && \
  91         (bufnum) <= NBuffers \
  92 )
  93
  94 /*
  95  * BufferIsPinned
  96  *              True iff the buffer is pinned (also checks for valid buffer number).
  97  *
  98  *              NOTE: what we check here is that *this* backend holds a pin on
  99  *              the buffer.  We do not care whether some other backend does.
 100  */
 101 #define BufferIsPinned(bufnum) \
 102 ( \
 103         !BufferIsValid(bufnum) ? \
 104                 false \
 105         : \
 106                 BufferIsLocal(bufnum) ? \
 107                         (LocalRefCount[-(bufnum) - 1] > 0) \
 108                 : \
 109                         (PrivateRefCount[(bufnum) - 1] > 0) \
 110 )
 111
 112 /*
 113  * BufferGetBlock
 114  *              Returns a reference to a disk page image associated with a buffer.
 115  *
 116  * Note:
 117  *              Assumes buffer is valid.
 118  */
 119 #define BufferGetBlock(buffer) \
 120 ( \
 121         AssertMacro(BufferIsValid(buffer)), \
 122         BufferIsLocal(buffer) ? \
 123                 LocalBufferBlockPointers[-(buffer) - 1] \
 124         : \
 125                 (Block) (BufferBlocks + ((Size) ((buffer) - 1)) * BLCKSZ) \
 126 )
 127
 128 /*
 129  * BufferGetPageSize
 130  *              Returns the page size within a buffer.
 131  *
 132  * Notes:
 133  *              Assumes buffer is valid.
 134  *
 135  *              The buffer can be a raw disk block and need not contain a valid
 136  *              (formatted) disk page.
 137  */
 138 /* XXX should dig out of buffer descriptor */
 139 #define BufferGetPageSize(buffer) \
 140 ( \
 141         AssertMacro(BufferIsValid(buffer)), \
 142         (Size)BLCKSZ \
 143 )
 144
 145 /*
 146  * BufferGetPage
 147  *              Returns the page associated with a buffer.
 148  */
 149 #define BufferGetPage(buffer) ((Page)BufferGetBlock(buffer))
 150
 151 /*
 152  * prototypes for functions in bufmgr.c
 153  */
 154 extern Buffer ReadBuffer(Relation reln, BlockNumber blockNum);
 155 extern Buffer ReadBufferExtended(Relation reln, ForkNumber forkNum,
 156                                                                  BlockNumber blockNum, ReadBufferMode mode,
 157                                                                  BufferAccessStrategy strategy);
 158 extern Buffer ReadBufferWithoutRelcache(RelFileNode rnode, bool isTemp,
 159                                                 ForkNumber forkNum, BlockNumber blockNum,
 160                                                 ReadBufferMode mode, BufferAccessStrategy strategy);
 161 extern void ReleaseBuffer(Buffer buffer);
 162 extern void UnlockReleaseBuffer(Buffer buffer);
 163 extern void MarkBufferDirty(Buffer buffer);
 164 extern void IncrBufferRefCount(Buffer buffer);
 165 extern Buffer ReleaseAndReadBuffer(Buffer buffer, Relation relation,
 166                                          BlockNumber blockNum);
 167
 168 extern void InitBufferPool(void);
 169 extern void InitBufferPoolAccess(void);
 170 extern void InitBufferPoolBackend(void);
 171 extern char *ShowBufferUsage(void);
 172 extern void ResetBufferUsage(void);
 173 extern void AtEOXact_Buffers(bool isCommit);
 174 extern void PrintBufferLeakWarning(Buffer buffer);
 175 extern void CheckPointBuffers(int flags);
 176 extern BlockNumber BufferGetBlockNumber(Buffer buffer);
 177 extern BlockNumber RelationGetNumberOfBlocks(Relation relation);
 178 extern void RelationTruncate(Relation rel, BlockNumber nblocks);
 179 extern void FlushRelationBuffers(Relation rel);
 180 extern void FlushDatabaseBuffers(Oid dbid);
 181 extern void DropRelFileNodeBuffers(RelFileNode rnode, ForkNumber forkNum,
 182                                            bool istemp, BlockNumber firstDelBlock);
 183 extern void DropDatabaseBuffers(Oid dbid);
 184
 185 #ifdef NOT_USED
 186 extern void PrintPinnedBufs(void);
 187 #endif
 188 extern Size BufferShmemSize(void);
 189 extern void BufferGetTag(Buffer buffer, RelFileNode *rnode,
 190                                                  ForkNumber *forknum, BlockNumber *blknum);
 191
 192 extern void SetBufferCommitInfoNeedsSave(Buffer buffer);
 193
 194 extern void UnlockBuffers(void);
 195 extern void LockBuffer(Buffer buffer, int mode);
 196 extern bool ConditionalLockBuffer(Buffer buffer);
 197 extern void LockBufferForCleanup(Buffer buffer);
 198 extern bool ConditionalLockBufferForCleanup(Buffer buffer);
 199
 200 extern void AbortBufferIO(void);
 201
 202 extern void BufmgrCommit(void);
 203 extern void BgBufferSync(void);
 204
 205 extern void AtProcExit_LocalBuffers(void);
 206
 207 /* in freelist.c */
 208 extern BufferAccessStrategy GetAccessStrategy(BufferAccessStrategyType btype);
 209 extern void FreeAccessStrategy(BufferAccessStrategy strategy);
 210
 211 #endif