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Overview
Comment:Only error out on a database file move when attempting to start a write transaction. Assume read transactions are still safe. And make the error SQLITE_READONLY_DBMOVED instead of SQLITE_IOERR_NODB.
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SHA1: 28348f2ada98c616241a51aecb70b63e87e6ddbb
User & Date: drh 2013-12-06 17:23:38
Context
2013-12-06
19:58
Add the SQLITE_READONLY_DBMOVED error code to the sqlite3ErrName() function. (check-in: 7789f801 user: mistachkin tags: detect-moved-db)
17:23
Only error out on a database file move when attempting to start a write transaction. Assume read transactions are still safe. And make the error SQLITE_READONLY_DBMOVED instead of SQLITE_IOERR_NODB. (check-in: 28348f2a user: drh tags: detect-moved-db)
15:37
Add code to detect if the database file is moved or deleted out from under SQLite and return an SQLITE_IOERR_NODB. (check-in: 8759a8e4 user: drh tags: detect-moved-db)
Changes
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Changes to src/pager.c. 

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  *ppPager = pPager;
  return SQLITE_OK;
}


/* Verify that the database file has not be deleted or renamed out from
** under the pager.  Return SQLITE_OK if the database is still were it ought
** to be on disk.  Return non-zero (SQLITE_IOERR_NODB or some other error
** code from sqlite3OsAccess()) if the database has gone missing.
*/
static int databaseIsUnmoved(Pager *pPager){
  const int fixedFlags = SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN |
                         SQLITE_IOCAP_UNMOVABLE_WHEN_OPEN;
  int dc;
  int x = 0, rc;
................................................................................

  if( pPager->tempFile ) return SQLITE_OK;
  if( pPager->dbSize==0 ) return SQLITE_OK;
  assert( pPager->zFilename && pPager->zFilename[0] );
  dc = sqlite3OsDeviceCharacteristics(pPager->fd);
  if( (dc&fixedFlags)==fixedFlags ) return SQLITE_OK;
  rc = sqlite3OsAccess(pPager->pVfs, pPager->zFilename, SQLITE_ACCESS_EXISTS, &x);
  if( rc==SQLITE_OK && !x ) rc = SQLITE_IOERR_NODB;
  return rc;
}


/*
** This function is called after transitioning from PAGER_UNLOCK to
** PAGER_SHARED state. It tests if there is a hot journal present in
................................................................................

    rc = pager_wait_on_lock(pPager, SHARED_LOCK);
    if( rc!=SQLITE_OK ){
      assert( pPager->eLock==NO_LOCK || pPager->eLock==UNKNOWN_LOCK );
      goto failed;
    }

    /* Verify that the database is unmoved and undeleted */
    rc = databaseIsUnmoved(pPager);
    if( rc ) goto failed;

    /* If a journal file exists, and there is no RESERVED lock on the
    ** database file, then it either needs to be played back or deleted.
    */
    if( pPager->eLock<=SHARED_LOCK ){
      rc = hasHotJournal(pPager, &bHotJournal);
    }
    if( rc!=SQLITE_OK ){
................................................................................
      }else{
        const int flags =                   /* VFS flags to open journal file */
          SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|
          (pPager->tempFile ? 
            (SQLITE_OPEN_DELETEONCLOSE|SQLITE_OPEN_TEMP_JOURNAL):
            (SQLITE_OPEN_MAIN_JOURNAL)
          );





  #ifdef SQLITE_ENABLE_ATOMIC_WRITE
        rc = sqlite3JournalOpen(
            pVfs, pPager->zJournal, pPager->jfd, flags, jrnlBufferSize(pPager)
        );
  #else
        rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, flags, 0);
  #endif

      }
      assert( rc!=SQLITE_OK || isOpen(pPager->jfd) );
    }
  
  
    /* Write the first journal header to the journal file and open 
    ** the sub-journal if necessary.








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  *ppPager = pPager;
  return SQLITE_OK;
}


/* Verify that the database file has not be deleted or renamed out from
** under the pager.  Return SQLITE_OK if the database is still were it ought
** to be on disk.  Return non-zero (SQLITE_READONLY_DBMOVED or some other error
** code from sqlite3OsAccess()) if the database has gone missing.
*/
static int databaseIsUnmoved(Pager *pPager){
  const int fixedFlags = SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN |
                         SQLITE_IOCAP_UNMOVABLE_WHEN_OPEN;
  int dc;
  int x = 0, rc;
................................................................................

  if( pPager->tempFile ) return SQLITE_OK;
  if( pPager->dbSize==0 ) return SQLITE_OK;
  assert( pPager->zFilename && pPager->zFilename[0] );
  dc = sqlite3OsDeviceCharacteristics(pPager->fd);
  if( (dc&fixedFlags)==fixedFlags ) return SQLITE_OK;
  rc = sqlite3OsAccess(pPager->pVfs, pPager->zFilename, SQLITE_ACCESS_EXISTS, &x);
  if( rc==SQLITE_OK && !x ) rc = SQLITE_READONLY_DBMOVED;
  return rc;
}


/*
** This function is called after transitioning from PAGER_UNLOCK to
** PAGER_SHARED state. It tests if there is a hot journal present in
................................................................................

    rc = pager_wait_on_lock(pPager, SHARED_LOCK);
    if( rc!=SQLITE_OK ){
      assert( pPager->eLock==NO_LOCK || pPager->eLock==UNKNOWN_LOCK );
      goto failed;
    }





    /* If a journal file exists, and there is no RESERVED lock on the
    ** database file, then it either needs to be played back or deleted.
    */
    if( pPager->eLock<=SHARED_LOCK ){
      rc = hasHotJournal(pPager, &bHotJournal);
    }
    if( rc!=SQLITE_OK ){
................................................................................
      }else{
        const int flags =                   /* VFS flags to open journal file */
          SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|
          (pPager->tempFile ? 
            (SQLITE_OPEN_DELETEONCLOSE|SQLITE_OPEN_TEMP_JOURNAL):
            (SQLITE_OPEN_MAIN_JOURNAL)
          );

        /* Verify that the database still has the same name as it did when
        ** it was originally opened. */
        rc = databaseIsUnmoved(pPager);
        if( rc==SQLITE_OK ){
#ifdef SQLITE_ENABLE_ATOMIC_WRITE
          rc = sqlite3JournalOpen(
              pVfs, pPager->zJournal, pPager->jfd, flags, jrnlBufferSize(pPager)
          );
#else
          rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, flags, 0);
#endif
        }
      }
      assert( rc!=SQLITE_OK || isOpen(pPager->jfd) );
    }
  
  
    /* Write the first journal header to the journal file and open 
    ** the sub-journal if necessary.

Changes to src/sqlite.h.in. 

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#define SQLITE_IOERR_SHMLOCK           (SQLITE_IOERR | (20<<8))
#define SQLITE_IOERR_SHMMAP            (SQLITE_IOERR | (21<<8))
#define SQLITE_IOERR_SEEK              (SQLITE_IOERR | (22<<8))
#define SQLITE_IOERR_DELETE_NOENT      (SQLITE_IOERR | (23<<8))
#define SQLITE_IOERR_MMAP              (SQLITE_IOERR | (24<<8))
#define SQLITE_IOERR_GETTEMPPATH       (SQLITE_IOERR | (25<<8))
#define SQLITE_IOERR_CONVPATH          (SQLITE_IOERR | (26<<8))
#define SQLITE_IOERR_NODB              (SQLITE_IOERR | (27<<8))
#define SQLITE_LOCKED_SHAREDCACHE      (SQLITE_LOCKED |  (1<<8))
#define SQLITE_BUSY_RECOVERY           (SQLITE_BUSY   |  (1<<8))
#define SQLITE_BUSY_SNAPSHOT           (SQLITE_BUSY   |  (2<<8))
#define SQLITE_CANTOPEN_NOTEMPDIR      (SQLITE_CANTOPEN | (1<<8))
#define SQLITE_CANTOPEN_ISDIR          (SQLITE_CANTOPEN | (2<<8))
#define SQLITE_CANTOPEN_FULLPATH       (SQLITE_CANTOPEN | (3<<8))
#define SQLITE_CANTOPEN_CONVPATH       (SQLITE_CANTOPEN | (4<<8))
#define SQLITE_CORRUPT_VTAB            (SQLITE_CORRUPT | (1<<8))
#define SQLITE_READONLY_RECOVERY       (SQLITE_READONLY | (1<<8))
#define SQLITE_READONLY_CANTLOCK       (SQLITE_READONLY | (2<<8))
#define SQLITE_READONLY_ROLLBACK       (SQLITE_READONLY | (3<<8))

#define SQLITE_ABORT_ROLLBACK          (SQLITE_ABORT | (2<<8))
#define SQLITE_CONSTRAINT_CHECK        (SQLITE_CONSTRAINT | (1<<8))
#define SQLITE_CONSTRAINT_COMMITHOOK   (SQLITE_CONSTRAINT | (2<<8))
#define SQLITE_CONSTRAINT_FOREIGNKEY   (SQLITE_CONSTRAINT | (3<<8))
#define SQLITE_CONSTRAINT_FUNCTION     (SQLITE_CONSTRAINT | (4<<8))
#define SQLITE_CONSTRAINT_NOTNULL      (SQLITE_CONSTRAINT | (5<<8))
#define SQLITE_CONSTRAINT_PRIMARYKEY   (SQLITE_CONSTRAINT | (6<<8))








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#define SQLITE_IOERR_SHMLOCK           (SQLITE_IOERR | (20<<8))
#define SQLITE_IOERR_SHMMAP            (SQLITE_IOERR | (21<<8))
#define SQLITE_IOERR_SEEK              (SQLITE_IOERR | (22<<8))
#define SQLITE_IOERR_DELETE_NOENT      (SQLITE_IOERR | (23<<8))
#define SQLITE_IOERR_MMAP              (SQLITE_IOERR | (24<<8))
#define SQLITE_IOERR_GETTEMPPATH       (SQLITE_IOERR | (25<<8))
#define SQLITE_IOERR_CONVPATH          (SQLITE_IOERR | (26<<8))

#define SQLITE_LOCKED_SHAREDCACHE      (SQLITE_LOCKED |  (1<<8))
#define SQLITE_BUSY_RECOVERY           (SQLITE_BUSY   |  (1<<8))
#define SQLITE_BUSY_SNAPSHOT           (SQLITE_BUSY   |  (2<<8))
#define SQLITE_CANTOPEN_NOTEMPDIR      (SQLITE_CANTOPEN | (1<<8))
#define SQLITE_CANTOPEN_ISDIR          (SQLITE_CANTOPEN | (2<<8))
#define SQLITE_CANTOPEN_FULLPATH       (SQLITE_CANTOPEN | (3<<8))
#define SQLITE_CANTOPEN_CONVPATH       (SQLITE_CANTOPEN | (4<<8))
#define SQLITE_CORRUPT_VTAB            (SQLITE_CORRUPT | (1<<8))
#define SQLITE_READONLY_RECOVERY       (SQLITE_READONLY | (1<<8))
#define SQLITE_READONLY_CANTLOCK       (SQLITE_READONLY | (2<<8))
#define SQLITE_READONLY_ROLLBACK       (SQLITE_READONLY | (3<<8))
#define SQLITE_READONLY_DBMOVED        (SQLITE_READONLY | (4<<8))
#define SQLITE_ABORT_ROLLBACK          (SQLITE_ABORT | (2<<8))
#define SQLITE_CONSTRAINT_CHECK        (SQLITE_CONSTRAINT | (1<<8))
#define SQLITE_CONSTRAINT_COMMITHOOK   (SQLITE_CONSTRAINT | (2<<8))
#define SQLITE_CONSTRAINT_FOREIGNKEY   (SQLITE_CONSTRAINT | (3<<8))
#define SQLITE_CONSTRAINT_FUNCTION     (SQLITE_CONSTRAINT | (4<<8))
#define SQLITE_CONSTRAINT_NOTNULL      (SQLITE_CONSTRAINT | (5<<8))
#define SQLITE_CONSTRAINT_PRIMARYKEY   (SQLITE_CONSTRAINT | (6<<8))

Changes to src/test_vfstrace.c. 

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    case SQLITE_IOERR_SHMOPEN:      zVal = "SQLITE_IOERR_SHMOPEN";      break;
    case SQLITE_IOERR_SHMSIZE:      zVal = "SQLITE_IOERR_SHMSIZE";      break;
    case SQLITE_IOERR_SHMLOCK:      zVal = "SQLITE_IOERR_SHMLOCK";      break;
    case SQLITE_IOERR_SHMMAP:       zVal = "SQLITE_IOERR_SHMMAP";       break;
    case SQLITE_IOERR_SEEK:         zVal = "SQLITE_IOERR_SEEK";         break;
    case SQLITE_IOERR_GETTEMPPATH:  zVal = "SQLITE_IOERR_GETTEMPPATH";  break;
    case SQLITE_IOERR_CONVPATH:     zVal = "SQLITE_IOERR_CONVPATH";     break;
    case SQLITE_IOERR_NODB:         zVal = "SQLITE_IOERR_NODB";         break;
    case SQLITE_LOCKED_SHAREDCACHE: zVal = "SQLITE_LOCKED_SHAREDCACHE"; break;
    case SQLITE_BUSY_RECOVERY:      zVal = "SQLITE_BUSY_RECOVERY";      break;
    case SQLITE_CANTOPEN_NOTEMPDIR: zVal = "SQLITE_CANTOPEN_NOTEMPDIR"; break;
    default: {
       sqlite3_snprintf(sizeof(zBuf), zBuf, "%d", rc);
       zVal = zBuf;
       break;








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    case SQLITE_IOERR_SHMOPEN:      zVal = "SQLITE_IOERR_SHMOPEN";      break;
    case SQLITE_IOERR_SHMSIZE:      zVal = "SQLITE_IOERR_SHMSIZE";      break;
    case SQLITE_IOERR_SHMLOCK:      zVal = "SQLITE_IOERR_SHMLOCK";      break;
    case SQLITE_IOERR_SHMMAP:       zVal = "SQLITE_IOERR_SHMMAP";       break;
    case SQLITE_IOERR_SEEK:         zVal = "SQLITE_IOERR_SEEK";         break;
    case SQLITE_IOERR_GETTEMPPATH:  zVal = "SQLITE_IOERR_GETTEMPPATH";  break;
    case SQLITE_IOERR_CONVPATH:     zVal = "SQLITE_IOERR_CONVPATH";     break;
    case SQLITE_READONLY_DBMOVED:   zVal = "SQLITE_READONLY_DBMOVED";   break;
    case SQLITE_LOCKED_SHAREDCACHE: zVal = "SQLITE_LOCKED_SHAREDCACHE"; break;
    case SQLITE_BUSY_RECOVERY:      zVal = "SQLITE_BUSY_RECOVERY";      break;
    case SQLITE_CANTOPEN_NOTEMPDIR: zVal = "SQLITE_CANTOPEN_NOTEMPDIR"; break;
    default: {
       sqlite3_snprintf(sizeof(zBuf), zBuf, "%d", rc);
       zVal = zBuf;
       break;

Changes to test/pager4.test. 

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#

if {$tcl_platform(platform)!="unix"} return

set testdir [file dirname $argv0]
source $testdir/tester.tcl



do_execsql_test pager4-1.1 {
  CREATE TABLE t1(a,b,c);
  INSERT INTO t1 VALUES(673,'stone','philips');
  SELECT * FROM t1;
} {673 stone philips}




file delete -force test-xyz.db
file rename test.db test-xyz.db
do_catchsql_test pager4-1.2 {
  SELECT * FROM t1;
} {1 {disk I/O error}}















































finish_test








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#

if {$tcl_platform(platform)!="unix"} return

set testdir [file dirname $argv0]
source $testdir/tester.tcl

# Create a database file for testing
#
do_execsql_test pager4-1.1 {
  CREATE TABLE t1(a,b,c);
  INSERT INTO t1 VALUES(673,'stone','philips');
  SELECT * FROM t1;
} {673 stone philips}

# After renaming the database file while it is open, one can still
# read from the database, but writing returns a READONLY error.
#
file delete -force test-xyz.db
file rename test.db test-xyz.db
do_catchsql_test pager4-1.2 {
  SELECT * FROM t1;

} {0 {673 stone philips}}
do_catchsql_test pager4-1.3 {
  UPDATE t1 SET a=537;
} {1 {attempt to write a readonly database}}

# Changing the name back clears the READONLY error
#
file rename test-xyz.db test.db
do_catchsql_test pager4-1.4 {
  SELECT * FROM t1;
} {0 {673 stone philips}}
do_catchsql_test pager4-1.5 {
  UPDATE t1 SET a=537;
  SELECT * FROM t1;
} {0 {537 stone philips}}

# We can write to a renamed database if journal_mode=OFF or
# journal_mode=MEMORY.
#
file rename test.db test-xyz.db
do_catchsql_test pager4-1.6 {
  PRAGMA journal_mode=OFF;
  UPDATE t1 SET a=107;
  SELECT * FROM t1;
} {0 {off 107 stone philips}}
do_catchsql_test pager4-1.7 {
  PRAGMA journal_mode=MEMORY;
  UPDATE t1 SET b='magpie';
  SELECT * FROM t1;
} {0 {memory 107 magpie philips}}

# Any other journal mode gives a READONLY error
#
do_catchsql_test pager4-1.8 {
  PRAGMA journal_mode=DELETE;
  UPDATE t1 SET c='jaguar';
} {1 {attempt to write a readonly database}}
do_catchsql_test pager4-1.9 {
  PRAGMA journal_mode=TRUNCATE;
  UPDATE t1 SET c='jaguar';
} {1 {attempt to write a readonly database}}
do_catchsql_test pager4-1.10 {
  PRAGMA journal_mode=PERSIST;
  UPDATE t1 SET c='jaguar';
} {1 {attempt to write a readonly database}}


finish_test

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