src/include/storage/bufmgr.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * bufmgr.h
   4  *        POSTGRES buffer manager definitions.
   5  *
   6  *
   7  * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
   8  * Portions Copyright (c) 1994, Regents of the University of California
   9  *
  10  * src/include/storage/bufmgr.h
  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 #include "utils/snapmgr.h"
  23
  24 typedef void *Block;
  25
  26 /* Possible arguments for GetAccessStrategy() */
  27 typedef enum BufferAccessStrategyType
  28 {
  29         BAS_NORMAL,                                     /* Normal random access */
  30         BAS_BULKREAD,                           /* Large read-only scan (hint bit updates are
  31                                                                  * ok) */
  32         BAS_BULKWRITE,                          /* Large multi-block write (e.g. COPY IN) */
  33         BAS_VACUUM                                      /* VACUUM */
  34 } BufferAccessStrategyType;
  35
  36 /* Possible modes for ReadBufferExtended() */
  37 typedef enum
  38 {
  39         RBM_NORMAL,                                     /* Normal read */
  40         RBM_ZERO_AND_LOCK,                      /* Don't read from disk, caller will
  41                                                                  * initialize. Also locks the page. */
  42         RBM_ZERO_AND_CLEANUP_LOCK,      /* Like RBM_ZERO_AND_LOCK, but locks the page
  43                                                                  * in "cleanup" mode */
  44         RBM_ZERO_ON_ERROR,                      /* Read, but return an all-zeros page on error */
  45         RBM_NORMAL_NO_LOG                       /* Don't log page as invalid during WAL
  46                                                                  * replay; otherwise same as RBM_NORMAL */
  47 } ReadBufferMode;
  48
  49 /*
  50  * Type returned by PrefetchBuffer().
  51  */
  52 typedef struct PrefetchBufferResult
  53 {
  54         Buffer          recent_buffer;  /* If valid, a hit (recheck needed!) */
  55         bool            initiated_io;   /* If true, a miss resulting in async I/O */
  56 } PrefetchBufferResult;
  57
  58 /* forward declared, to avoid having to expose buf_internals.h here */
  59 struct WritebackContext;
  60
  61 /* forward declared, to avoid including smgr.h here */
  62 struct SMgrRelationData;
  63
  64 /* in globals.c ... this duplicates miscadmin.h */
  65 extern PGDLLIMPORT int NBuffers;
  66
  67 /* in bufmgr.c */
  68 extern bool zero_damaged_pages;
  69 extern int      bgwriter_lru_maxpages;
  70 extern double bgwriter_lru_multiplier;
  71 extern bool track_io_timing;
  72 extern int      effective_io_concurrency;
  73 extern int      maintenance_io_concurrency;
  74
  75 extern int      checkpoint_flush_after;
  76 extern int      backend_flush_after;
  77 extern int      bgwriter_flush_after;
  78
  79 /* in buf_init.c */
  80 extern PGDLLIMPORT char *BufferBlocks;
  81
  82 /* in localbuf.c */
  83 extern PGDLLIMPORT int NLocBuffer;
  84 extern PGDLLIMPORT Block *LocalBufferBlockPointers;
  85 extern PGDLLIMPORT int32 *LocalRefCount;
  86
  87 /* upper limit for effective_io_concurrency */
  88 #define MAX_IO_CONCURRENCY 1000
  89
  90 /* special block number for ReadBuffer() */
  91 #define P_NEW   InvalidBlockNumber      /* grow the file to get a new page */
  92
  93 /*
  94  * Buffer content lock modes (mode argument for LockBuffer())
  95  */
  96 #define BUFFER_LOCK_UNLOCK              0
  97 #define BUFFER_LOCK_SHARE               1
  98 #define BUFFER_LOCK_EXCLUSIVE   2
  99
 100 /*
 101  * These routines are beaten on quite heavily, hence the macroization.
 102  */
 103
 104 /*
 105  * BufferIsValid
 106  *              True iff the given buffer number is valid (either as a shared
 107  *              or local buffer).
 108  *
 109  * Note: For a long time this was defined the same as BufferIsPinned,
 110  * that is it would say False if you didn't hold a pin on the buffer.
 111  * I believe this was bogus and served only to mask logic errors.
 112  * Code should always know whether it has a buffer reference,
 113  * independently of the pin state.
 114  *
 115  * Note: For a further long time this was not quite the inverse of the
 116  * BufferIsInvalid() macro, in that it also did sanity checks to verify
 117  * that the buffer number was in range.  Most likely, this macro was
 118  * originally intended only to be used in assertions, but its use has
 119  * since expanded quite a bit, and the overhead of making those checks
 120  * even in non-assert-enabled builds can be significant.  Thus, we've
 121  * now demoted the range checks to assertions within the macro itself.
 122  */
 123 #define BufferIsValid(bufnum) \
 124 ( \
 125         AssertMacro((bufnum) <= NBuffers && (bufnum) >= -NLocBuffer), \
 126         (bufnum) != InvalidBuffer  \
 127 )
 128
 129 /*
 130  * BufferGetBlock
 131  *              Returns a reference to a disk page image associated with a buffer.
 132  *
 133  * Note:
 134  *              Assumes buffer is valid.
 135  */
 136 #define BufferGetBlock(buffer) \
 137 ( \
 138         AssertMacro(BufferIsValid(buffer)), \
 139         BufferIsLocal(buffer) ? \
 140                 LocalBufferBlockPointers[-(buffer) - 1] \
 141         : \
 142                 (Block) (BufferBlocks + ((Size) ((buffer) - 1)) * BLCKSZ) \
 143 )
 144
 145 /*
 146  * BufferGetPageSize
 147  *              Returns the page size within a buffer.
 148  *
 149  * Notes:
 150  *              Assumes buffer is valid.
 151  *
 152  *              The buffer can be a raw disk block and need not contain a valid
 153  *              (formatted) disk page.
 154  */
 155 /* XXX should dig out of buffer descriptor */
 156 #define BufferGetPageSize(buffer) \
 157 ( \
 158         AssertMacro(BufferIsValid(buffer)), \
 159         (Size)BLCKSZ \
 160 )
 161
 162 /*
 163  * BufferGetPage
 164  *              Returns the page associated with a buffer.
 165  *
 166  * When this is called as part of a scan, there may be a need for a nearby
 167  * call to TestForOldSnapshot().  See the definition of that for details.
 168  */
 169 #define BufferGetPage(buffer) ((Page)BufferGetBlock(buffer))
 170
 171 /*
 172  * prototypes for functions in bufmgr.c
 173  */
 174 extern PrefetchBufferResult PrefetchSharedBuffer(struct SMgrRelationData *smgr_reln,
 175                                                                                                  ForkNumber forkNum,
 176                                                                                                  BlockNumber blockNum);
 177 extern PrefetchBufferResult PrefetchBuffer(Relation reln, ForkNumber forkNum,
 178                                                                                    BlockNumber blockNum);
 179 extern bool ReadRecentBuffer(RelFileNode rnode, ForkNumber forkNum,
 180                                                          BlockNumber blockNum, Buffer recent_buffer);
 181 extern Buffer ReadBuffer(Relation reln, BlockNumber blockNum);
 182 extern Buffer ReadBufferExtended(Relation reln, ForkNumber forkNum,
 183                                                                  BlockNumber blockNum, ReadBufferMode mode,
 184                                                                  BufferAccessStrategy strategy);
 185 extern Buffer ReadBufferWithoutRelcache(RelFileNode rnode,
 186                                                                                 ForkNumber forkNum, BlockNumber blockNum,
 187                                                                                 ReadBufferMode mode, BufferAccessStrategy strategy);
 188 extern void ReleaseBuffer(Buffer buffer);
 189 extern void UnlockReleaseBuffer(Buffer buffer);
 190 extern void MarkBufferDirty(Buffer buffer);
 191 extern void IncrBufferRefCount(Buffer buffer);
 192 extern Buffer ReleaseAndReadBuffer(Buffer buffer, Relation relation,
 193                                                                    BlockNumber blockNum);
 194
 195 extern void InitBufferPool(void);
 196 extern void InitBufferPoolAccess(void);
 197 extern void AtEOXact_Buffers(bool isCommit);
 198 extern void PrintBufferLeakWarning(Buffer buffer);
 199 extern void CheckPointBuffers(int flags);
 200 extern BlockNumber BufferGetBlockNumber(Buffer buffer);
 201 extern BlockNumber RelationGetNumberOfBlocksInFork(Relation relation,
 202                                                                                                    ForkNumber forkNum);
 203 extern void FlushOneBuffer(Buffer buffer);
 204 extern void FlushRelationBuffers(Relation rel);
 205 extern void FlushRelationsAllBuffers(struct SMgrRelationData **smgrs, int nrels);
 206 extern void FlushDatabaseBuffers(Oid dbid);
 207 extern void DropRelFileNodeBuffers(struct SMgrRelationData *smgr_reln, ForkNumber *forkNum,
 208                                                                    int nforks, BlockNumber *firstDelBlock);
 209 extern void DropRelFileNodesAllBuffers(struct SMgrRelationData **smgr_reln, int nnodes);
 210 extern void DropDatabaseBuffers(Oid dbid);
 211
 212 #define RelationGetNumberOfBlocks(reln) \
 213         RelationGetNumberOfBlocksInFork(reln, MAIN_FORKNUM)
 214
 215 extern bool BufferIsPermanent(Buffer buffer);
 216 extern XLogRecPtr BufferGetLSNAtomic(Buffer buffer);
 217
 218 #ifdef NOT_USED
 219 extern void PrintPinnedBufs(void);
 220 #endif
 221 extern Size BufferShmemSize(void);
 222 extern void BufferGetTag(Buffer buffer, RelFileNode *rnode,
 223                                                  ForkNumber *forknum, BlockNumber *blknum);
 224
 225 extern void MarkBufferDirtyHint(Buffer buffer, bool buffer_std);
 226
 227 extern void UnlockBuffers(void);
 228 extern void LockBuffer(Buffer buffer, int mode);
 229 extern bool ConditionalLockBuffer(Buffer buffer);
 230 extern void LockBufferForCleanup(Buffer buffer);
 231 extern bool ConditionalLockBufferForCleanup(Buffer buffer);
 232 extern bool IsBufferCleanupOK(Buffer buffer);
 233 extern bool HoldingBufferPinThatDelaysRecovery(void);
 234
 235 extern void AbortBufferIO(void);
 236
 237 extern void BufmgrCommit(void);
 238 extern bool BgBufferSync(struct WritebackContext *wb_context);
 239
 240 extern void AtProcExit_LocalBuffers(void);
 241
 242 extern void TestForOldSnapshot_impl(Snapshot snapshot, Relation relation);
 243
 244 /* in freelist.c */
 245 extern BufferAccessStrategy GetAccessStrategy(BufferAccessStrategyType btype);
 246 extern void FreeAccessStrategy(BufferAccessStrategy strategy);
 247
 248
 249 /* inline functions */
 250
 251 /*
 252  * Although this header file is nominally backend-only, certain frontend
 253  * programs like pg_waldump include it.  For compilers that emit static
 254  * inline functions even when they're unused, that leads to unsatisfied
 255  * external references; hence hide these with #ifndef FRONTEND.
 256  */
 257
 258 #ifndef FRONTEND
 259
 260 /*
 261  * Check whether the given snapshot is too old to have safely read the given
 262  * page from the given table.  If so, throw a "snapshot too old" error.
 263  *
 264  * This test generally needs to be performed after every BufferGetPage() call
 265  * that is executed as part of a scan.  It is not needed for calls made for
 266  * modifying the page (for example, to position to the right place to insert a
 267  * new index tuple or for vacuuming).  It may also be omitted where calls to
 268  * lower-level functions will have already performed the test.
 269  *
 270  * Note that a NULL snapshot argument is allowed and causes a fast return
 271  * without error; this is to support call sites which can be called from
 272  * either scans or index modification areas.
 273  *
 274  * For best performance, keep the tests that are fastest and/or most likely to
 275  * exclude a page from old snapshot testing near the front.
 276  */
 277 static inline void
 278 TestForOldSnapshot(Snapshot snapshot, Relation relation, Page page)
 279 {
 280         Assert(relation != NULL);
 281
 282         if (old_snapshot_threshold >= 0
 283                 && (snapshot) != NULL
 284                 && ((snapshot)->snapshot_type == SNAPSHOT_MVCC
 285                         || (snapshot)->snapshot_type == SNAPSHOT_TOAST)
 286                 && !XLogRecPtrIsInvalid((snapshot)->lsn)
 287                 && PageGetLSN(page) > (snapshot)->lsn)
 288                 TestForOldSnapshot_impl(snapshot, relation);
 289 }
 290
 291 #endif                                                  /* FRONTEND */
 292
 293 #endif                                                  /* BUFMGR_H */