/ Check-in [671ba5fc]
Login
SQLite training in Houston TX on 2019-11-05 (details)
Part of the 2019 Tcl Conference

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

Overview
Comment:Only open a read-only connection to shared-memory if the "readonly_shm=1" option is specified as part of the database file URI (and if a read-write connection fails).
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | wal-readonly
Files: files | file ages | folders
SHA1: 671ba5fc59f7a958e5a4138d2425b1173a442ad7
User & Date: dan 2011-05-11 14:57:33
Context
2011-05-11
15:53
Merge latest trunk changes. Add a couple of readonly shm tests. check-in: cde45a03 user: dan tags: wal-readonly
14:57
Only open a read-only connection to shared-memory if the "readonly_shm=1" option is specified as part of the database file URI (and if a read-write connection fails). check-in: 671ba5fc user: dan tags: wal-readonly
2011-05-10
17:31
Add experimental support for read-only connections to WAL databases. check-in: bb59f986 user: dan tags: wal-readonly
Changes
Hide Diffs Unified Diffs Show Whitespace Changes Patch

Changes to src/attach.c.

72
73
74
75
76
77
78


79
80
81
82
83
84
85
...
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
  const char *zFile;
  char *zPath = 0;
  char *zErr = 0;
  unsigned int flags;
  Db *aNew;
  char *zErrDyn = 0;
  sqlite3_vfs *pVfs;



  UNUSED_PARAMETER(NotUsed);

  zFile = (const char *)sqlite3_value_text(argv[0]);
  zName = (const char *)sqlite3_value_text(argv[1]);
  if( zFile==0 ) zFile = "";
  if( zName==0 ) zName = "";
................................................................................
  memset(aNew, 0, sizeof(*aNew));

  /* Open the database file. If the btree is successfully opened, use
  ** it to obtain the database schema. At this point the schema may
  ** or may not be initialised.
  */
  flags = db->openFlags;
  rc = sqlite3ParseUri(db->pVfs->zName, zFile, &flags, &pVfs, &zPath, &zErr);
  if( rc!=SQLITE_OK ){
    if( rc==SQLITE_NOMEM ) db->mallocFailed = 1;
    sqlite3_result_error(context, zErr, -1);
    sqlite3_free(zErr);
    return;
  }
  assert( pVfs );
  flags |= SQLITE_OPEN_MAIN_DB;
  rc = sqlite3BtreeOpen(pVfs, zPath, db, &aNew->pBt, 0, flags);
  sqlite3_free( zPath );
  db->nDb++;
  if( rc==SQLITE_CONSTRAINT ){
    rc = SQLITE_ERROR;
    zErrDyn = sqlite3MPrintf(db, "database is already attached");
  }else if( rc==SQLITE_OK ){
    Pager *pPager;







>
>







 







|








|







72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
...
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
  const char *zFile;
  char *zPath = 0;
  char *zErr = 0;
  unsigned int flags;
  Db *aNew;
  char *zErrDyn = 0;
  sqlite3_vfs *pVfs;
  const char *zVfs = db->pVfs->zName;       /* Name of default (main) VFS */
  int btflags = 0;

  UNUSED_PARAMETER(NotUsed);

  zFile = (const char *)sqlite3_value_text(argv[0]);
  zName = (const char *)sqlite3_value_text(argv[1]);
  if( zFile==0 ) zFile = "";
  if( zName==0 ) zName = "";
................................................................................
  memset(aNew, 0, sizeof(*aNew));

  /* Open the database file. If the btree is successfully opened, use
  ** it to obtain the database schema. At this point the schema may
  ** or may not be initialised.
  */
  flags = db->openFlags;
  rc = sqlite3ParseUri(zVfs, zFile, &flags, &btflags, &pVfs, &zPath, &zErr);
  if( rc!=SQLITE_OK ){
    if( rc==SQLITE_NOMEM ) db->mallocFailed = 1;
    sqlite3_result_error(context, zErr, -1);
    sqlite3_free(zErr);
    return;
  }
  assert( pVfs );
  flags |= SQLITE_OPEN_MAIN_DB;
  rc = sqlite3BtreeOpen(pVfs, zPath, db, &aNew->pBt, btflags, flags);
  sqlite3_free( zPath );
  db->nDb++;
  if( rc==SQLITE_CONSTRAINT ){
    rc = SQLITE_ERROR;
    zErrDyn = sqlite3MPrintf(db, "database is already attached");
  }else if( rc==SQLITE_OK ){
    Pager *pPager;

Changes to src/btree.h.

57
58
59
60
61
62
63

64
65
66
67
68
69
70
** pager.h.
*/
#define BTREE_OMIT_JOURNAL  1  /* Do not create or use a rollback journal */
#define BTREE_NO_READLOCK   2  /* Omit readlocks on readonly files */
#define BTREE_MEMORY        4  /* This is an in-memory DB */
#define BTREE_SINGLE        8  /* The file contains at most 1 b-tree */
#define BTREE_UNORDERED    16  /* Use of a hash implementation is OK */


int sqlite3BtreeClose(Btree*);
int sqlite3BtreeSetCacheSize(Btree*,int);
int sqlite3BtreeSetSafetyLevel(Btree*,int,int,int);
int sqlite3BtreeSyncDisabled(Btree*);
int sqlite3BtreeSetPageSize(Btree *p, int nPagesize, int nReserve, int eFix);
int sqlite3BtreeGetPageSize(Btree*);







>







57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
** pager.h.
*/
#define BTREE_OMIT_JOURNAL  1  /* Do not create or use a rollback journal */
#define BTREE_NO_READLOCK   2  /* Omit readlocks on readonly files */
#define BTREE_MEMORY        4  /* This is an in-memory DB */
#define BTREE_SINGLE        8  /* The file contains at most 1 b-tree */
#define BTREE_UNORDERED    16  /* Use of a hash implementation is OK */
#define BTREE_READONLYSHM  32  /* Read-only SHM access is acceptable */

int sqlite3BtreeClose(Btree*);
int sqlite3BtreeSetCacheSize(Btree*,int);
int sqlite3BtreeSetSafetyLevel(Btree*,int,int,int);
int sqlite3BtreeSyncDisabled(Btree*);
int sqlite3BtreeSetPageSize(Btree *p, int nPagesize, int nReserve, int eFix);
int sqlite3BtreeGetPageSize(Btree*);

Changes to src/main.c.

1814
1815
1816
1817
1818
1819
1820

1821
1822
1823
1824
1825
1826
1827
....
1929
1930
1931
1932
1933
1934
1935






1936
1937
1938
1939
1940
1941
1942
....
2032
2033
2034
2035
2036
2037
2038

2039
2040
2041
2042
2043
2044
2045
....
2159
2160
2161
2162
2163
2164
2165
2166

2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
** message. It is the responsibility of the caller to eventually release
** this buffer by calling sqlite3_free().
*/
int sqlite3ParseUri(
  const char *zDefaultVfs,        /* VFS to use if no "vfs=xxx" query option */
  const char *zUri,               /* Nul-terminated URI to parse */
  unsigned int *pFlags,           /* IN/OUT: SQLITE_OPEN_XXX flags */

  sqlite3_vfs **ppVfs,            /* OUT: VFS to use */ 
  char **pzFile,                  /* OUT: Filename component of URI */
  char **pzErrMsg                 /* OUT: Error message (if rc!=SQLITE_OK) */
){
  int rc = SQLITE_OK;
  unsigned int flags = *pFlags;
  const char *zVfs = zDefaultVfs;
................................................................................
    while( zOpt[0] ){
      int nOpt = sqlite3Strlen30(zOpt);
      char *zVal = &zOpt[nOpt+1];
      int nVal = sqlite3Strlen30(zVal);

      if( nOpt==3 && memcmp("vfs", zOpt, 3)==0 ){
        zVfs = zVal;






      }else{
        struct OpenMode {
          const char *z;
          int mode;
        } *aMode = 0;
        char *zModeType;
        int mask;
................................................................................
  const char *zVfs       /* Name of the VFS to use */
){
  sqlite3 *db;                    /* Store allocated handle here */
  int rc;                         /* Return code */
  int isThreadsafe;               /* True for threadsafe connections */
  char *zOpen = 0;                /* Filename argument to pass to BtreeOpen() */
  char *zErrMsg = 0;              /* Error message from sqlite3ParseUri() */


  *ppDb = 0;
#ifndef SQLITE_OMIT_AUTOINIT
  rc = sqlite3_initialize();
  if( rc ) return rc;
#endif

................................................................................
  assert( db->pDfltColl!=0 );

  /* Also add a UTF-8 case-insensitive collation sequence. */
  createCollation(db, "NOCASE", SQLITE_UTF8, SQLITE_COLL_NOCASE, 0,
                  nocaseCollatingFunc, 0);

  /* Parse the filename/URI argument. */
  rc = sqlite3ParseUri(zVfs, zFilename, &flags, &db->pVfs, &zOpen, &zErrMsg);

  if( rc!=SQLITE_OK ){
    if( rc==SQLITE_NOMEM ) db->mallocFailed = 1;
    sqlite3Error(db, rc, zErrMsg ? "%s" : 0, zErrMsg);
    sqlite3_free(zErrMsg);
    goto opendb_out;
  }

  /* Open the backend database driver */
  db->openFlags = flags;
  rc = sqlite3BtreeOpen(db->pVfs, zOpen, db, &db->aDb[0].pBt, 0,
                        flags | SQLITE_OPEN_MAIN_DB);
  if( rc!=SQLITE_OK ){
    if( rc==SQLITE_IOERR_NOMEM ){
      rc = SQLITE_NOMEM;
    }
    sqlite3Error(db, rc, 0);
    goto opendb_out;







>







 







>
>
>
>
>
>







 







>







 







|
>









|







1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
....
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
....
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
....
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
** message. It is the responsibility of the caller to eventually release
** this buffer by calling sqlite3_free().
*/
int sqlite3ParseUri(
  const char *zDefaultVfs,        /* VFS to use if no "vfs=xxx" query option */
  const char *zUri,               /* Nul-terminated URI to parse */
  unsigned int *pFlags,           /* IN/OUT: SQLITE_OPEN_XXX flags */
  int *pBtflags,                  /* IN/OUT: BTREE_XXX flags */
  sqlite3_vfs **ppVfs,            /* OUT: VFS to use */ 
  char **pzFile,                  /* OUT: Filename component of URI */
  char **pzErrMsg                 /* OUT: Error message (if rc!=SQLITE_OK) */
){
  int rc = SQLITE_OK;
  unsigned int flags = *pFlags;
  const char *zVfs = zDefaultVfs;
................................................................................
    while( zOpt[0] ){
      int nOpt = sqlite3Strlen30(zOpt);
      char *zVal = &zOpt[nOpt+1];
      int nVal = sqlite3Strlen30(zVal);

      if( nOpt==3 && memcmp("vfs", zOpt, 3)==0 ){
        zVfs = zVal;
      }else if( nOpt==12 && memcmp("readonly_shm", zOpt, 12)==0 ){
        if( sqlite3Atoi(zVal) ){
          *pBtflags |= BTREE_READONLYSHM;
        }else{
          *pBtflags &= ~BTREE_READONLYSHM;
        }
      }else{
        struct OpenMode {
          const char *z;
          int mode;
        } *aMode = 0;
        char *zModeType;
        int mask;
................................................................................
  const char *zVfs       /* Name of the VFS to use */
){
  sqlite3 *db;                    /* Store allocated handle here */
  int rc;                         /* Return code */
  int isThreadsafe;               /* True for threadsafe connections */
  char *zOpen = 0;                /* Filename argument to pass to BtreeOpen() */
  char *zErrMsg = 0;              /* Error message from sqlite3ParseUri() */
  int btflags = 0;                /* Mask of BTREE_XXX flags */

  *ppDb = 0;
#ifndef SQLITE_OMIT_AUTOINIT
  rc = sqlite3_initialize();
  if( rc ) return rc;
#endif

................................................................................
  assert( db->pDfltColl!=0 );

  /* Also add a UTF-8 case-insensitive collation sequence. */
  createCollation(db, "NOCASE", SQLITE_UTF8, SQLITE_COLL_NOCASE, 0,
                  nocaseCollatingFunc, 0);

  /* Parse the filename/URI argument. */
  rc = sqlite3ParseUri(
      zVfs, zFilename, &flags, &btflags, &db->pVfs, &zOpen, &zErrMsg);
  if( rc!=SQLITE_OK ){
    if( rc==SQLITE_NOMEM ) db->mallocFailed = 1;
    sqlite3Error(db, rc, zErrMsg ? "%s" : 0, zErrMsg);
    sqlite3_free(zErrMsg);
    goto opendb_out;
  }

  /* Open the backend database driver */
  db->openFlags = flags;
  rc = sqlite3BtreeOpen(db->pVfs, zOpen, db, &db->aDb[0].pBt, btflags,
                        flags | SQLITE_OPEN_MAIN_DB);
  if( rc!=SQLITE_OK ){
    if( rc==SQLITE_IOERR_NOMEM ){
      rc = SQLITE_NOMEM;
    }
    sqlite3Error(db, rc, 0);
    goto opendb_out;

Changes to src/pager.c.

616
617
618
619
620
621
622

623
624
625
626
627
628
629
....
3013
3014
3015
3016
3017
3018
3019

3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
....
4410
4411
4412
4413
4414
4415
4416

4417
4418
4419
4420
4421
4422
4423
  u8 noSync;                  /* Do not sync the journal if true */
  u8 fullSync;                /* Do extra syncs of the journal for robustness */
  u8 ckptSyncFlags;           /* SYNC_NORMAL or SYNC_FULL for checkpoint */
  u8 syncFlags;               /* SYNC_NORMAL or SYNC_FULL otherwise */
  u8 tempFile;                /* zFilename is a temporary file */
  u8 readOnly;                /* True for a read-only database */
  u8 memDb;                   /* True to inhibit all file I/O */


  /**************************************************************************
  ** The following block contains those class members that change during
  ** routine opertion.  Class members not in this block are either fixed
  ** when the pager is first created or else only change when there is a
  ** significant mode change (such as changing the page_size, locking_mode,
  ** or the journal_mode).  From another view, these class members describe
................................................................................
** makes a snapshot of the database at the current point in time and preserves
** that snapshot for use by the reader in spite of concurrently changes by
** other writers or checkpointers.
*/
static int pagerBeginReadTransaction(Pager *pPager){
  int rc;                         /* Return code */
  int changed = 0;                /* True if cache must be reset */


  assert( pagerUseWal(pPager) );
  assert( pPager->eState==PAGER_OPEN || pPager->eState==PAGER_READER );

  /* sqlite3WalEndReadTransaction() was not called for the previous
  ** transaction in locking_mode=EXCLUSIVE.  So call it now.  If we
  ** are in locking_mode=NORMAL and EndRead() was previously called,
  ** the duplicate call is harmless.
  */
  sqlite3WalEndReadTransaction(pPager->pWal);

  rc = sqlite3WalBeginReadTransaction(pPager->pWal, &changed);
  if( rc!=SQLITE_OK || changed ){
    pager_reset(pPager);
  }

  return rc;
}
#endif
................................................................................
    memcpy(pPager->zWal, zPathname, nPathname);
    memcpy(&pPager->zWal[nPathname], "-wal", 4);
#endif
    sqlite3_free(zPathname);
  }
  pPager->pVfs = pVfs;
  pPager->vfsFlags = vfsFlags;


  /* Open the pager file.
  */
  if( zFilename && zFilename[0] ){
    int fout = 0;                    /* VFS flags returned by xOpen() */
    rc = sqlite3OsOpen(pVfs, pPager->zFilename, pPager->fd, vfsFlags, &fout);
    assert( !memDb );







>







 







>









|

|







 







>







616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
....
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
....
4412
4413
4414
4415
4416
4417
4418
4419
4420
4421
4422
4423
4424
4425
4426
  u8 noSync;                  /* Do not sync the journal if true */
  u8 fullSync;                /* Do extra syncs of the journal for robustness */
  u8 ckptSyncFlags;           /* SYNC_NORMAL or SYNC_FULL for checkpoint */
  u8 syncFlags;               /* SYNC_NORMAL or SYNC_FULL otherwise */
  u8 tempFile;                /* zFilename is a temporary file */
  u8 readOnly;                /* True for a read-only database */
  u8 memDb;                   /* True to inhibit all file I/O */
  u8 readOnlyShm;             /* True if read-only shm access is Ok */

  /**************************************************************************
  ** The following block contains those class members that change during
  ** routine opertion.  Class members not in this block are either fixed
  ** when the pager is first created or else only change when there is a
  ** significant mode change (such as changing the page_size, locking_mode,
  ** or the journal_mode).  From another view, these class members describe
................................................................................
** makes a snapshot of the database at the current point in time and preserves
** that snapshot for use by the reader in spite of concurrently changes by
** other writers or checkpointers.
*/
static int pagerBeginReadTransaction(Pager *pPager){
  int rc;                         /* Return code */
  int changed = 0;                /* True if cache must be reset */
  Wal *pWal = pPager->pWal;

  assert( pagerUseWal(pPager) );
  assert( pPager->eState==PAGER_OPEN || pPager->eState==PAGER_READER );

  /* sqlite3WalEndReadTransaction() was not called for the previous
  ** transaction in locking_mode=EXCLUSIVE.  So call it now.  If we
  ** are in locking_mode=NORMAL and EndRead() was previously called,
  ** the duplicate call is harmless.
  */
  sqlite3WalEndReadTransaction(pWal);

  rc = sqlite3WalBeginReadTransaction(pWal, pPager->readOnlyShm, &changed);
  if( rc!=SQLITE_OK || changed ){
    pager_reset(pPager);
  }

  return rc;
}
#endif
................................................................................
    memcpy(pPager->zWal, zPathname, nPathname);
    memcpy(&pPager->zWal[nPathname], "-wal", 4);
#endif
    sqlite3_free(zPathname);
  }
  pPager->pVfs = pVfs;
  pPager->vfsFlags = vfsFlags;
  pPager->readOnlyShm = (flags & PAGER_READONLYSHM)!=0;

  /* Open the pager file.
  */
  if( zFilename && zFilename[0] ){
    int fout = 0;                    /* VFS flags returned by xOpen() */
    rc = sqlite3OsOpen(pVfs, pPager->zFilename, pPager->fd, vfsFlags, &fout);
    assert( !memDb );

Changes to src/pager.h.

56
57
58
59
60
61
62

63
64
65
66
67
68
69
** Allowed values for the flags parameter to sqlite3PagerOpen().
**
** NOTE: These values must match the corresponding BTREE_ values in btree.h.
*/
#define PAGER_OMIT_JOURNAL  0x0001    /* Do not use a rollback journal */
#define PAGER_NO_READLOCK   0x0002    /* Omit readlocks on readonly files */
#define PAGER_MEMORY        0x0004    /* In-memory database */


/*
** Valid values for the second argument to sqlite3PagerLockingMode().
*/
#define PAGER_LOCKINGMODE_QUERY      -1
#define PAGER_LOCKINGMODE_NORMAL      0
#define PAGER_LOCKINGMODE_EXCLUSIVE   1







>







56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
** Allowed values for the flags parameter to sqlite3PagerOpen().
**
** NOTE: These values must match the corresponding BTREE_ values in btree.h.
*/
#define PAGER_OMIT_JOURNAL  0x0001    /* Do not use a rollback journal */
#define PAGER_NO_READLOCK   0x0002    /* Omit readlocks on readonly files */
#define PAGER_MEMORY        0x0004    /* In-memory database */
#define PAGER_READONLYSHM   0x0020    /* Read-only SHM access is acceptable */

/*
** Valid values for the second argument to sqlite3PagerLockingMode().
*/
#define PAGER_LOCKINGMODE_QUERY      -1
#define PAGER_LOCKINGMODE_NORMAL      0
#define PAGER_LOCKINGMODE_EXCLUSIVE   1

Changes to src/sqliteInt.h.

2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
void sqlite3AddNotNull(Parse*, int);
void sqlite3AddPrimaryKey(Parse*, ExprList*, int, int, int);
void sqlite3AddCheckConstraint(Parse*, Expr*);
void sqlite3AddColumnType(Parse*,Token*);
void sqlite3AddDefaultValue(Parse*,ExprSpan*);
void sqlite3AddCollateType(Parse*, Token*);
void sqlite3EndTable(Parse*,Token*,Token*,Select*);
int sqlite3ParseUri(const char*,const char*,unsigned int*,
                    sqlite3_vfs**,char**,char **);

Bitvec *sqlite3BitvecCreate(u32);
int sqlite3BitvecTest(Bitvec*, u32);
int sqlite3BitvecSet(Bitvec*, u32);
void sqlite3BitvecClear(Bitvec*, u32, void*);
void sqlite3BitvecDestroy(Bitvec*);







|







2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
void sqlite3AddNotNull(Parse*, int);
void sqlite3AddPrimaryKey(Parse*, ExprList*, int, int, int);
void sqlite3AddCheckConstraint(Parse*, Expr*);
void sqlite3AddColumnType(Parse*,Token*);
void sqlite3AddDefaultValue(Parse*,ExprSpan*);
void sqlite3AddCollateType(Parse*, Token*);
void sqlite3EndTable(Parse*,Token*,Token*,Select*);
int sqlite3ParseUri(const char*,const char*,unsigned int*,int*,
                    sqlite3_vfs**,char**,char **);

Bitvec *sqlite3BitvecCreate(u32);
int sqlite3BitvecTest(Bitvec*, u32);
int sqlite3BitvecSet(Bitvec*, u32);
void sqlite3BitvecClear(Bitvec*, u32, void*);
void sqlite3BitvecDestroy(Bitvec*);

Changes to src/wal.c.

525
526
527
528
529
530
531
532

533
534
535
536
537
538
539
540
541
542
543
544
545

546

547
548
549
550
551
552
553
....
1905
1906
1907
1908
1909
1910
1911

1912
1913
1914
1915
1916
1917
1918
....
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206




2207
2208
2209

2210
2211
2212
2213
2214
2215
2216
    if( pWal->exclusiveMode==WAL_HEAPMEMORY_MODE ){
      pWal->apWiData[iPage] = (u32 volatile *)sqlite3MallocZero(WALINDEX_PGSZ);
      if( !pWal->apWiData[iPage] ) rc = SQLITE_NOMEM;
    }else{
      rc = sqlite3OsShmMap(pWal->pDbFd, iPage, WALINDEX_PGSZ, 
          pWal->writeLock, (void volatile **)&pWal->apWiData[iPage]
      );
      if( rc==SQLITE_CANTOPEN && iPage==0 ){

        sqlite3OsFileControl(pWal->pDbFd, SQLITE_FCNTL_READONLY_SHM, (void*)1);
        rc = sqlite3OsShmMap(pWal->pDbFd, iPage, WALINDEX_PGSZ, 
            pWal->writeLock, (void volatile **)&pWal->apWiData[iPage]
        );
        if( rc==SQLITE_OK ){
          pWal->readOnly = pWal->readOnlyShm = 1;
        }
        sqlite3OsFileControl(pWal->pDbFd, SQLITE_FCNTL_READONLY_SHM, (void*)0);
      }
    }
  }

  *ppPage = pWal->apWiData[iPage];

  assert( iPage==0 || *ppPage || rc!=SQLITE_OK );

  return rc;
}

/*
** Return a pointer to the WalCkptInfo structure in the wal-index.
*/
static volatile WalCkptInfo *walCkptInfo(Wal *pWal){
................................................................................
  */
  assert( pChanged );
  rc = walIndexPage(pWal, 0, &page0);
  if( rc!=SQLITE_OK ){
    return rc;
  };
  assert( page0 || pWal->writeLock==0 );


  /* If the first page of the wal-index has been mapped, try to read the
  ** wal-index header immediately, without holding any lock. This usually
  ** works, but may fail if the wal-index header is corrupt or currently 
  ** being modified by another thread or process.
  */
  badHdr = (page0 ? walIndexTryHdr(pWal, pChanged) : 1);
................................................................................
** that extra content is ignored by the current thread.
**
** If the database contents have changes since the previous read
** transaction, then *pChanged is set to 1 before returning.  The
** Pager layer will use this to know that is cache is stale and
** needs to be flushed.
*/
int sqlite3WalBeginReadTransaction(Wal *pWal, int *pChanged){
  int rc;                         /* Return code */
  int cnt = 0;                    /* Number of TryBeginRead attempts */





  do{
    rc = walTryBeginRead(pWal, pChanged, 0, ++cnt);
  }while( rc==WAL_RETRY );

  testcase( (rc&0xff)==SQLITE_BUSY );
  testcase( (rc&0xff)==SQLITE_IOERR );
  testcase( rc==SQLITE_PROTOCOL );
  testcase( rc==SQLITE_OK );
  return rc;
}








|
>











<

>

>







 







>







 







|



>
>
>
>



>







525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544

545
546
547
548
549
550
551
552
553
554
555
....
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
....
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
    if( pWal->exclusiveMode==WAL_HEAPMEMORY_MODE ){
      pWal->apWiData[iPage] = (u32 volatile *)sqlite3MallocZero(WALINDEX_PGSZ);
      if( !pWal->apWiData[iPage] ) rc = SQLITE_NOMEM;
    }else{
      rc = sqlite3OsShmMap(pWal->pDbFd, iPage, WALINDEX_PGSZ, 
          pWal->writeLock, (void volatile **)&pWal->apWiData[iPage]
      );
      if( rc==SQLITE_CANTOPEN && pWal->readOnlyShm>1 ){
        assert( iPage==0 );
        sqlite3OsFileControl(pWal->pDbFd, SQLITE_FCNTL_READONLY_SHM, (void*)1);
        rc = sqlite3OsShmMap(pWal->pDbFd, iPage, WALINDEX_PGSZ, 
            pWal->writeLock, (void volatile **)&pWal->apWiData[iPage]
        );
        if( rc==SQLITE_OK ){
          pWal->readOnly = pWal->readOnlyShm = 1;
        }
        sqlite3OsFileControl(pWal->pDbFd, SQLITE_FCNTL_READONLY_SHM, (void*)0);
      }
    }
  }

  *ppPage = pWal->apWiData[iPage];

  assert( iPage==0 || *ppPage || rc!=SQLITE_OK );
  if( pWal->readOnlyShm>1 ) pWal->readOnlyShm = 0;
  return rc;
}

/*
** Return a pointer to the WalCkptInfo structure in the wal-index.
*/
static volatile WalCkptInfo *walCkptInfo(Wal *pWal){
................................................................................
  */
  assert( pChanged );
  rc = walIndexPage(pWal, 0, &page0);
  if( rc!=SQLITE_OK ){
    return rc;
  };
  assert( page0 || pWal->writeLock==0 );
  assert( pWal->readOnlyShm==0 || pWal->readOnlyShm==1 );

  /* If the first page of the wal-index has been mapped, try to read the
  ** wal-index header immediately, without holding any lock. This usually
  ** works, but may fail if the wal-index header is corrupt or currently 
  ** being modified by another thread or process.
  */
  badHdr = (page0 ? walIndexTryHdr(pWal, pChanged) : 1);
................................................................................
** that extra content is ignored by the current thread.
**
** If the database contents have changes since the previous read
** transaction, then *pChanged is set to 1 before returning.  The
** Pager layer will use this to know that is cache is stale and
** needs to be flushed.
*/
int sqlite3WalBeginReadTransaction(Wal *pWal, int readOnlyShm, int *pChanged){
  int rc;                         /* Return code */
  int cnt = 0;                    /* Number of TryBeginRead attempts */

  if( pWal->nWiData==0 || pWal->apWiData[0]==0 ){
    assert( readOnlyShm==0 || readOnlyShm==1 );
    pWal->readOnlyShm = readOnlyShm*2;
  }
  do{
    rc = walTryBeginRead(pWal, pChanged, 0, ++cnt);
  }while( rc==WAL_RETRY );
  assert( rc || pWal->readOnlyShm==0 || (readOnlyShm && pWal->readOnlyShm==1) );
  testcase( (rc&0xff)==SQLITE_BUSY );
  testcase( (rc&0xff)==SQLITE_IOERR );
  testcase( rc==SQLITE_PROTOCOL );
  testcase( rc==SQLITE_OK );
  return rc;
}

Changes to src/wal.h.

18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
..
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
#define _WAL_H_

#include "sqliteInt.h"

#ifdef SQLITE_OMIT_WAL
# define sqlite3WalOpen(x,y,z)                   0
# define sqlite3WalClose(w,x,y,z)                0
# define sqlite3WalBeginReadTransaction(y,z)     0
# define sqlite3WalEndReadTransaction(z)
# define sqlite3WalRead(v,w,x,y,z)               0
# define sqlite3WalDbsize(y)                     0
# define sqlite3WalBeginWriteTransaction(y)      0
# define sqlite3WalEndWriteTransaction(x)        0
# define sqlite3WalUndo(x,y,z)                   0
# define sqlite3WalSavepoint(y,z)
................................................................................
/* Used by readers to open (lock) and close (unlock) a snapshot.  A 
** snapshot is like a read-transaction.  It is the state of the database
** at an instant in time.  sqlite3WalOpenSnapshot gets a read lock and
** preserves the current state even if the other threads or processes
** write to or checkpoint the WAL.  sqlite3WalCloseSnapshot() closes the
** transaction and releases the lock.
*/
int sqlite3WalBeginReadTransaction(Wal *pWal, int *);
void sqlite3WalEndReadTransaction(Wal *pWal);

/* Read a page from the write-ahead log, if it is present. */
int sqlite3WalRead(Wal *pWal, Pgno pgno, int *pInWal, int nOut, u8 *pOut);

/* If the WAL is not empty, return the size of the database. */
Pgno sqlite3WalDbsize(Wal *pWal);







|







 







|







18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
..
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
#define _WAL_H_

#include "sqliteInt.h"

#ifdef SQLITE_OMIT_WAL
# define sqlite3WalOpen(x,y,z)                   0
# define sqlite3WalClose(w,x,y,z)                0
# define sqlite3WalBeginReadTransaction(x,y,z)   0
# define sqlite3WalEndReadTransaction(z)
# define sqlite3WalRead(v,w,x,y,z)               0
# define sqlite3WalDbsize(y)                     0
# define sqlite3WalBeginWriteTransaction(y)      0
# define sqlite3WalEndWriteTransaction(x)        0
# define sqlite3WalUndo(x,y,z)                   0
# define sqlite3WalSavepoint(y,z)
................................................................................
/* Used by readers to open (lock) and close (unlock) a snapshot.  A 
** snapshot is like a read-transaction.  It is the state of the database
** at an instant in time.  sqlite3WalOpenSnapshot gets a read lock and
** preserves the current state even if the other threads or processes
** write to or checkpoint the WAL.  sqlite3WalCloseSnapshot() closes the
** transaction and releases the lock.
*/
int sqlite3WalBeginReadTransaction(Wal *pWal, int, int *);
void sqlite3WalEndReadTransaction(Wal *pWal);

/* Read a page from the write-ahead log, if it is present. */
int sqlite3WalRead(Wal *pWal, Pgno pgno, int *pInWal, int nOut, u8 *pOut);

/* If the WAL is not empty, return the size of the database. */
Pgno sqlite3WalDbsize(Wal *pWal);

Changes to test/walro.test.

30
31
32
33
34
35
36







37
38
39
40
41
42
43
..
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
..
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
  # Close all connections and delete the database.
  #
  code1 { db close  }
  code2 { db2 close }
  code3 { db3 close }
  forcedelete test.db
  forcedelete walro








  file mkdir walro

  do_test 1.1.1 {
    code2 { sqlite3 db2 test.db }
    sql2 { 
      PRAGMA journal_mode = WAL;
................................................................................
      INSERT INTO t1 VALUES('a', 'b');
    }
    file exists test.db-shm
  } {1}

  do_test 1.1.2 {
    file attributes test.db-shm -permissions r--r--r--
    code1 { sqlite3 db test.db }
  } {}

  do_test 1.1.3 { sql1 "SELECT * FROM t1" }                {a b}
  do_test 1.1.4 { sql2 "INSERT INTO t1 VALUES('c', 'd')" } {}
  do_test 1.1.5 { sql1 "SELECT * FROM t1" }                {a b c d}

  # Check that the read-only connection cannot write or checkpoint the db.
................................................................................

  do_test 1.2.1 {
    code2 { db2 close }
    code1 { db close }
    list [file exists test.db-wal] [file exists test.db-shm]
  } {1 1}
  do_test 1.2.2 {
    code1 { sqlite3 db test.db }
    sql1 { SELECT * FROM t1 }
  } {a b c d e f g h i j}

  do_test 1.2.3 {
    code1 { db close }
    file attributes test.db-shm -permissions rw-r--r--
    hexio_write test.db-shm 0 01020304 
    file attributes test.db-shm -permissions r--r--r--
    code1 { sqlite3 db test.db }
    csql1 { SELECT * FROM t1 }
  } {1 {attempt to write a readonly database}}
  do_test 1.2.4 {
    code1 { sqlite3_extended_errcode db } 
  } {SQLITE_READONLY_RECOVERY}

  do_test 1.2.5 {







>
>
>
>
>
>
>







 







|







 







|








|







30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
..
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
..
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
  # Close all connections and delete the database.
  #
  code1 { db close  }
  code2 { db2 close }
  code3 { db3 close }
  forcedelete test.db
  forcedelete walro

  foreach c {code1 code2 code3} {
    $c {
      sqlite3_shutdown
      sqlite3_config_uri 1
    }
  }

  file mkdir walro

  do_test 1.1.1 {
    code2 { sqlite3 db2 test.db }
    sql2 { 
      PRAGMA journal_mode = WAL;
................................................................................
      INSERT INTO t1 VALUES('a', 'b');
    }
    file exists test.db-shm
  } {1}

  do_test 1.1.2 {
    file attributes test.db-shm -permissions r--r--r--
    code1 { sqlite3 db file:test.db?readonly_shm=1 }
  } {}

  do_test 1.1.3 { sql1 "SELECT * FROM t1" }                {a b}
  do_test 1.1.4 { sql2 "INSERT INTO t1 VALUES('c', 'd')" } {}
  do_test 1.1.5 { sql1 "SELECT * FROM t1" }                {a b c d}

  # Check that the read-only connection cannot write or checkpoint the db.
................................................................................

  do_test 1.2.1 {
    code2 { db2 close }
    code1 { db close }
    list [file exists test.db-wal] [file exists test.db-shm]
  } {1 1}
  do_test 1.2.2 {
    code1 { sqlite3 db file:test.db?readonly_shm=1 }
    sql1 { SELECT * FROM t1 }
  } {a b c d e f g h i j}

  do_test 1.2.3 {
    code1 { db close }
    file attributes test.db-shm -permissions rw-r--r--
    hexio_write test.db-shm 0 01020304 
    file attributes test.db-shm -permissions r--r--r--
    code1 { sqlite3 db file:test.db?readonly_shm=1 }
    csql1 { SELECT * FROM t1 }
  } {1 {attempt to write a readonly database}}
  do_test 1.2.4 {
    code1 { sqlite3_extended_errcode db } 
  } {SQLITE_READONLY_RECOVERY}

  do_test 1.2.5 {