SQLite

Check-in [a38858a24c]
Login

Many hyperlinks are disabled.
Use anonymous login to enable hyperlinks.

Overview
Comment:Avoid running recovery while there is another read/write client.
Downloads: Tarball | ZIP archive
Timelines: family | ancestors | descendants | both | server-edition
Files: files | file ages | folders
SHA3-256: a38858a24c6edaa05966b7e158e603bcbde8b05c6233e3bb005cfb32bc91ea06
User & Date: dan 2017-05-13 19:07:10.813
Context
2017-05-15
19:32
Avoid writer starvation by adding a RESERVED state to page locks. (check-in: 9b7f80246f user: dan tags: server-edition)
2017-05-13
19:07
Avoid running recovery while there is another read/write client. (check-in: a38858a24c user: dan tags: server-edition)
2017-05-12
18:52
Require exclusive access to the db to wrap the wal file. Have "PRAGMA wal_checkpoint = restart" block for this. (check-in: cbf44ed975 user: dan tags: server-edition)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/server.c.
508
509
510
511
512
513
514








515
516
      v = *pSlot;
    }
  }

server_lock_out:
  return rc;
}









#endif /* ifdef SQLITE_SERVER_EDITION */







>
>
>
>
>
>
>
>


508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
      v = *pSlot;
    }
  }

server_lock_out:
  return rc;
}

int sqlite3ServerHasLock(Server *p, Pgno pgno, int bWrite){
  u32 v = *serverPageLockSlot(p, pgno);
  if( bWrite ){
    return (v>>HMA_CLIENT_SLOTS)==(p->iClient+1);
  }
  return (v & (1 << p->iClient))!=0;
}

#endif /* ifdef SQLITE_SERVER_EDITION */
Changes to src/server.h.
24
25
26
27
28
29
30


31
32
33
34
void sqlite3ServerDisconnect(Server *p, sqlite3_file *dbfd);

int sqlite3ServerBegin(Server *p);
int sqlite3ServerEnd(Server *p);
int sqlite3ServerReleaseWriteLocks(Server *p);

int sqlite3ServerLock(Server *p, Pgno pgno, int bWrite, int bBlock);



#endif /* SQLITE_SERVER_H */

#endif /* SQLITE_SERVER_EDITION */







>
>




24
25
26
27
28
29
30
31
32
33
34
35
36
void sqlite3ServerDisconnect(Server *p, sqlite3_file *dbfd);

int sqlite3ServerBegin(Server *p);
int sqlite3ServerEnd(Server *p);
int sqlite3ServerReleaseWriteLocks(Server *p);

int sqlite3ServerLock(Server *p, Pgno pgno, int bWrite, int bBlock);

int sqlite3ServerHasLock(Server *p, Pgno pgno, int bWrite);

#endif /* SQLITE_SERVER_H */

#endif /* SQLITE_SERVER_EDITION */
Changes to src/wal.c.
2066
2067
2068
2069
2070
2071
2072








2073
2074
2075
2076
2077
2078
2079
    testcase( pWal->szPage<=32768 );
    testcase( pWal->szPage>=65536 );
  }

  /* The header was successfully read. Return zero. */
  return 0;
}









/*
** Read the wal-index header from the wal-index and into pWal->hdr.
** If the wal-header appears to be corrupt, try to reconstruct the
** wal-index from the WAL before returning.
**
** Set *pChanged to 1 if the wal-index header value in pWal->hdr is







>
>
>
>
>
>
>
>







2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
    testcase( pWal->szPage<=32768 );
    testcase( pWal->szPage>=65536 );
  }

  /* The header was successfully read. Return zero. */
  return 0;
}

static int walIndexWriteLock(Wal *pWal){
  if( walIsServer(pWal) ){
    return sqlite3ServerLock(pWal->pServer, 0, 1, 0);
  }else{
    return walLockExclusive(pWal, WAL_WRITE_LOCK, 1);
  }
}

/*
** Read the wal-index header from the wal-index and into pWal->hdr.
** If the wal-header appears to be corrupt, try to reconstruct the
** wal-index from the WAL before returning.
**
** Set *pChanged to 1 if the wal-index header value in pWal->hdr is
2107
2108
2109
2110
2111
2112
2113

2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131

2132

2133
2134
2135
2136
2137
2138
2139

  /* If the first attempt failed, it might have been due to a race
  ** with a writer.  So get a WRITE lock and try again.
  */
  assert( badHdr==0 || pWal->writeLock==0 );
  if( badHdr ){
    if( pWal->readOnly & WAL_SHM_RDONLY ){

      if( SQLITE_OK==(rc = walLockShared(pWal, WAL_WRITE_LOCK)) ){
        walUnlockShared(pWal, WAL_WRITE_LOCK);
        rc = SQLITE_READONLY_RECOVERY;
      }
    }else if( SQLITE_OK==(rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1)) ){
      pWal->writeLock = 1;
      if( SQLITE_OK==(rc = walIndexPage(pWal, 0, &page0)) ){
        badHdr = walIndexTryHdr(pWal, pChanged);
        if( badHdr ){
          /* If the wal-index header is still malformed even while holding
          ** a WRITE lock, it can only mean that the header is corrupted and
          ** needs to be reconstructed.  So run recovery to do exactly that.
          */
          rc = walIndexRecover(pWal);
          *pChanged = 1;
        }
      }
      pWal->writeLock = 0;

      walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1);

    }
  }

  /* If the header is read successfully, check the version number to make
  ** sure the wal-index was not constructed with some future format that
  ** this version of SQLite cannot understand.
  */







>




|













>
|
>







2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150

  /* If the first attempt failed, it might have been due to a race
  ** with a writer.  So get a WRITE lock and try again.
  */
  assert( badHdr==0 || pWal->writeLock==0 );
  if( badHdr ){
    if( pWal->readOnly & WAL_SHM_RDONLY ){
      assert( walIsServer(pWal)==0 );
      if( SQLITE_OK==(rc = walLockShared(pWal, WAL_WRITE_LOCK)) ){
        walUnlockShared(pWal, WAL_WRITE_LOCK);
        rc = SQLITE_READONLY_RECOVERY;
      }
    }else if( SQLITE_OK==(rc = walIndexWriteLock(pWal)) ){
      pWal->writeLock = 1;
      if( SQLITE_OK==(rc = walIndexPage(pWal, 0, &page0)) ){
        badHdr = walIndexTryHdr(pWal, pChanged);
        if( badHdr ){
          /* If the wal-index header is still malformed even while holding
          ** a WRITE lock, it can only mean that the header is corrupted and
          ** needs to be reconstructed.  So run recovery to do exactly that.
          */
          rc = walIndexRecover(pWal);
          *pChanged = 1;
        }
      }
      pWal->writeLock = 0;
      if( walIsServer(pWal)==0 ){
        walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1);
      }
    }
  }

  /* If the header is read successfully, check the version number to make
  ** sure the wal-index was not constructed with some future format that
  ** this version of SQLite cannot understand.
  */
2609
2610
2611
2612
2613
2614
2615



2616
2617
2618
2619
2620
2621
2622
  u32 iLast = pWal->hdr.mxFrame;  /* Last page in WAL for this reader */
  int iHash;                      /* Used to loop through N hash tables */
  int iMinHash;

  /* This routine is only be called from within a read transaction. */
  assert( walIsServer(pWal) || pWal->readLock>=0 || pWal->lockError );




  if( walIsServer(pWal) && pWal->writeLock==0 ){
    /* A server mode connection must read from the most recent snapshot. */
    iLast = walIndexHdr(pWal)->mxFrame;
  }

  /* If the "last page" field of the wal-index header snapshot is 0, then
  ** no data will be read from the wal under any circumstances. Return early







>
>
>







2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
  u32 iLast = pWal->hdr.mxFrame;  /* Last page in WAL for this reader */
  int iHash;                      /* Used to loop through N hash tables */
  int iMinHash;

  /* This routine is only be called from within a read transaction. */
  assert( walIsServer(pWal) || pWal->readLock>=0 || pWal->lockError );

  assert( walIsServer(pWal)==0 || pWal->writeLock==0 
       || sqlite3ServerHasLock(pWal->pServer, 0, 1) 
  );
  if( walIsServer(pWal) && pWal->writeLock==0 ){
    /* A server mode connection must read from the most recent snapshot. */
    iLast = walIndexHdr(pWal)->mxFrame;
  }

  /* If the "last page" field of the wal-index header snapshot is 0, then
  ** no data will be read from the wal under any circumstances. Return early
3105
3106
3107
3108
3109
3110
3111

3112
3113
3114
3115
3116
3117
3118
      pWal->writeLock = 1;
      rc = walIndexTryHdr(pWal, &bDummy);
    }
    if( rc!=SQLITE_OK ){
      return rc;
    }
  }


  /* If this frame set completes a transaction, then nTruncate>0.  If
  ** nTruncate==0 then this frame set does not complete the transaction. */
  assert( (isCommit!=0)==(nTruncate!=0) );

#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
  { int cnt; for(cnt=0, p=pList; p; p=p->pDirty, cnt++){}







>







3119
3120
3121
3122
3123
3124
3125
3126
3127
3128
3129
3130
3131
3132
3133
      pWal->writeLock = 1;
      rc = walIndexTryHdr(pWal, &bDummy);
    }
    if( rc!=SQLITE_OK ){
      return rc;
    }
  }
  assert( walIsServer(pWal)==0 || sqlite3ServerHasLock(pWal->pServer, 0, 1) );

  /* If this frame set completes a transaction, then nTruncate>0.  If
  ** nTruncate==0 then this frame set does not complete the transaction. */
  assert( (isCommit!=0)==(nTruncate!=0) );

#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
  { int cnt; for(cnt=0, p=pList; p; p=p->pDirty, cnt++){}