p2 = (sqlite3_snapshot*)sqlite3TestTextToPtr(Tcl_GetString(objv[2]));
  res = sqlite3_snapshot_cmp(p1, p2);
  Tcl_SetObjResult(interp, Tcl_NewIntObj(res));
  return TCL_OK;
}
#endif /* SQLITE_ENABLE_SNAPSHOT */












































































































/*
** Usage: sqlite3_delete_database FILENAME
*/
int sqlite3_delete_database(const char*);   /* in test_delete.c */
static int SQLITE_TCLAPI test_delete_database(
  void * clientData,
  Tcl_Interp *interp,
................................................................................
#endif
     { "vfs_current_time_int64",           vfsCurrentTimeInt64,   0 },
#ifdef SQLITE_ENABLE_SNAPSHOT
     { "sqlite3_snapshot_get", test_snapshot_get, 0 },
     { "sqlite3_snapshot_open", test_snapshot_open, 0 },
     { "sqlite3_snapshot_free", test_snapshot_free, 0 },
     { "sqlite3_snapshot_cmp", test_snapshot_cmp, 0 },



#endif
     { "sqlite3_delete_database", test_delete_database, 0 },
  };
  static int bitmask_size = sizeof(Bitmask)*8;
  static int longdouble_size = sizeof(LONGDOUBLE_TYPE);
  int i;
  extern int sqlite3_sync_count, sqlite3_fullsync_count;

  p2 = (sqlite3_snapshot*)sqlite3TestTextToPtr(Tcl_GetString(objv[2]));
  res = sqlite3_snapshot_cmp(p1, p2);
  Tcl_SetObjResult(interp, Tcl_NewIntObj(res));
  return TCL_OK;
}
#endif /* SQLITE_ENABLE_SNAPSHOT */

#ifdef SQLITE_ENABLE_SNAPSHOT
/*
** Usage: sqlite3_snapshot_get_blob DB DBNAME
*/
static int SQLITE_TCLAPI test_snapshot_get_blob(
  void * clientData,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){
  int rc;
  sqlite3 *db;
  char *zName;
  sqlite3_snapshot *pSnapshot = 0;

  if( objc!=3 ){
    Tcl_WrongNumArgs(interp, 1, objv, "DB DBNAME");
    return TCL_ERROR;
  }
  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
  zName = Tcl_GetString(objv[2]);

  rc = sqlite3_snapshot_get(db, zName, &pSnapshot);
  if( rc!=SQLITE_OK ){
    Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
    return TCL_ERROR;
  }else{
    Tcl_SetObjResult(interp, 
        Tcl_NewByteArrayObj((unsigned char*)pSnapshot, sizeof(sqlite3_snapshot))
    );
    sqlite3_snapshot_free(pSnapshot);
  }
  return TCL_OK;
}
#endif /* SQLITE_ENABLE_SNAPSHOT */

#ifdef SQLITE_ENABLE_SNAPSHOT
  /*
  ** Usage: sqlite3_snapshot_open_blob DB DBNAME SNAPSHOT
*/
static int SQLITE_TCLAPI test_snapshot_open_blob(
  void * clientData,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){
  int rc;
  sqlite3 *db;
  char *zName;
  unsigned char *pBlob;
  int nBlob;

  if( objc!=4 ){
    Tcl_WrongNumArgs(interp, 1, objv, "DB DBNAME SNAPSHOT");
    return TCL_ERROR;
  }
  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
  zName = Tcl_GetString(objv[2]);
  pBlob = Tcl_GetByteArrayFromObj(objv[3], &nBlob);
  if( nBlob!=sizeof(sqlite3_snapshot) ){
    Tcl_AppendResult(interp, "bad SNAPSHOT", 0);
    return TCL_ERROR;
  }
  rc = sqlite3_snapshot_open(db, zName, (sqlite3_snapshot*)pBlob);
  if( rc!=SQLITE_OK ){
    Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
    return TCL_ERROR;
  }
  return TCL_OK;
}
#endif /* SQLITE_ENABLE_SNAPSHOT */

#ifdef SQLITE_ENABLE_SNAPSHOT
/*
** Usage: sqlite3_snapshot_cmp_blob SNAPSHOT1 SNAPSHOT2
*/
static int SQLITE_TCLAPI test_snapshot_cmp_blob(
  void * clientData,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){
  int res;
  unsigned char *p1;
  unsigned char *p2;
  int n1;
  int n2;

  if( objc!=3 ){
    Tcl_WrongNumArgs(interp, 1, objv, "SNAPSHOT1 SNAPSHOT2");
    return TCL_ERROR;
  }

  p1 = Tcl_GetByteArrayFromObj(objv[1], &n1);
  p2 = Tcl_GetByteArrayFromObj(objv[2], &n2);

  if( n1!=sizeof(sqlite3_snapshot) || n1!=n2 ){
    Tcl_AppendResult(interp, "bad SNAPSHOT", 0);
    return TCL_ERROR;
  }

  res = sqlite3_snapshot_cmp((sqlite3_snapshot*)p1, (sqlite3_snapshot*)p2);
  Tcl_SetObjResult(interp, Tcl_NewIntObj(res));
  return TCL_OK;
}
#endif /* SQLITE_ENABLE_SNAPSHOT */

/*
** Usage: sqlite3_delete_database FILENAME
*/
int sqlite3_delete_database(const char*);   /* in test_delete.c */
static int SQLITE_TCLAPI test_delete_database(
  void * clientData,
  Tcl_Interp *interp,
................................................................................
#endif
     { "vfs_current_time_int64",           vfsCurrentTimeInt64,   0 },
#ifdef SQLITE_ENABLE_SNAPSHOT
     { "sqlite3_snapshot_get", test_snapshot_get, 0 },
     { "sqlite3_snapshot_open", test_snapshot_open, 0 },
     { "sqlite3_snapshot_free", test_snapshot_free, 0 },
     { "sqlite3_snapshot_cmp", test_snapshot_cmp, 0 },
     { "sqlite3_snapshot_get_blob", test_snapshot_get_blob, 0 },
     { "sqlite3_snapshot_open_blob", test_snapshot_open_blob, 0 },
     { "sqlite3_snapshot_cmp_blob", test_snapshot_cmp_blob, 0 },
#endif
     { "sqlite3_delete_database", test_delete_database, 0 },
  };
  static int bitmask_size = sizeof(Bitmask)*8;
  static int longdouble_size = sizeof(LONGDOUBLE_TYPE);
  int i;
  extern int sqlite3_sync_count, sqlite3_fullsync_count;

# is that each connection opened as part of this permutation executes
# "PRAGMA journal_mode=memory", which fails if the database is in wal mode
# and there are one or more existing connections.
if {[permutation]=="inmemory_journal"} {
  finish_test
  return
}



































#-------------------------------------------------------------------------
# Check some error conditions in snapshot_get(). It is an error if:
#
#  1) snapshot_get() is called on a non-WAL database, or
#  2) there is an open write transaction on the database.
#
do_execsql_test 1.0 {
  CREATE TABLE t1(a, b);
  INSERT INTO t1 VALUES(1, 2);
  INSERT INTO t1 VALUES(3, 4);
}

do_test 1.1.1 {
  execsql { BEGIN; SELECT * FROM t1; }
  list [catch { sqlite3_snapshot_get db main } msg] $msg
} {1 SQLITE_ERROR}
do_execsql_test 1.1.2 COMMIT

do_test 1.2.1 {
  execsql {
    PRAGMA journal_mode = WAL;
    BEGIN;
      INSERT INTO t1 VALUES(5, 6);
      INSERT INTO t1 VALUES(7, 8);
  }
  list [catch { sqlite3_snapshot_get db main } msg] $msg
} {1 SQLITE_ERROR}
do_execsql_test 1.3.2 COMMIT

#-------------------------------------------------------------------------
# Check that a simple case works. Reuse the database created by the
# block of tests above.
#
do_execsql_test 2.1.0 {
  BEGIN;
    SELECT * FROM t1;
} {1 2 3 4 5 6 7 8}

do_test 2.1.1 {
  set snapshot [sqlite3_snapshot_get db main]
  execsql {
    COMMIT;
    INSERT INTO t1 VALUES(9, 10);
    SELECT * FROM t1;
  }
} {1 2 3 4 5 6 7 8 9 10}

do_test 2.1.2 {
  execsql BEGIN
  sqlite3_snapshot_open db main $snapshot
  execsql {
    SELECT * FROM t1;
  }
} {1 2 3 4 5 6 7 8}

do_test 2.1.3 {
  sqlite3_snapshot_free $snapshot
  execsql COMMIT
} {}

do_test 2.2.0 {
  sqlite3 db2 test.db
  execsql {
    BEGIN;
      SELECT * FROM t1;
  } db2
} {1 2 3 4 5 6 7 8 9 10}

do_test 2.2.1 {
  set snapshot [sqlite3_snapshot_get db2 main]
  execsql {
    INSERT INTO t1 VALUES(11, 12);
    SELECT * FROM t1;
  }
} {1 2 3 4 5 6 7 8 9 10 11 12}

do_test 2.2.2 {
  execsql BEGIN
  sqlite3_snapshot_open db main $snapshot
  execsql {
    SELECT * FROM t1;
  }
} {1 2 3 4 5 6 7 8 9 10}

do_test 2.2.3 {
  sqlite3_snapshot_free $snapshot
  execsql COMMIT
  execsql COMMIT db2
  db2 close
} {}

do_test 2.3.1 {
  execsql { DELETE FROM t1 WHERE a>6 }
  set snapshot [sqlite3_snapshot_get db main]
  execsql {
    INSERT INTO t1 VALUES('a', 'b');
    INSERT INTO t1 VALUES('c', 'd');
    SELECT * FROM t1;
  }
} {1 2 3 4 5 6 a b c d}
do_test 2.3.2 {
  execsql BEGIN
  sqlite3_snapshot_open db main $snapshot
  execsql { SELECT * FROM t1 }
} {1 2 3 4 5 6}

do_test 2.3.3 {
  catchsql {
    INSERT INTO t1 VALUES('x','y')
  }
} {1 {database is locked}}
do_test 2.3.4 {
  execsql COMMIT
  sqlite3_snapshot_free $snapshot
} {}

#-------------------------------------------------------------------------
# Check some errors in sqlite3_snapshot_open(). It is an error if:
#
#   1) the db is in auto-commit mode,
#   2) the db has an open (read or write) transaction,
#   3) the db is not a wal database,
#
# Reuse the database created by earlier tests.
#
do_execsql_test 3.0.0 {
  CREATE TABLE t2(x, y);
  INSERT INTO t2 VALUES('a', 'b');
  INSERT INTO t2 VALUES('c', 'd');
  BEGIN;
    SELECT * FROM t2;
} {a b c d}
do_test 3.0.1 {
  set snapshot [sqlite3_snapshot_get db main]
  execsql { COMMIT }
  execsql { INSERT INTO t2 VALUES('e', 'f'); }
} {}

do_test 3.1 {
  list [catch {sqlite3_snapshot_open db main $snapshot } msg] $msg
} {1 SQLITE_ERROR}

do_test 3.2.1 {
  execsql {
    BEGIN;
      SELECT * FROM t2;
  }
} {a b c d e f}
do_test 3.2.2 {
  list [catch {sqlite3_snapshot_open db main $snapshot } msg] $msg
} {1 SQLITE_ERROR}

do_test 3.2.3 {
  execsql {
    COMMIT;
    BEGIN;
      INSERT INTO t2 VALUES('g', 'h');
  }
  list [catch {sqlite3_snapshot_open db main $snapshot } msg] $msg
} {1 SQLITE_ERROR}
do_execsql_test 3.2.4 COMMIT

do_test 3.3.1 {
  execsql { PRAGMA journal_mode = DELETE }
  execsql { BEGIN }
  list [catch {sqlite3_snapshot_open db main $snapshot } msg] $msg
} {1 SQLITE_ERROR}

do_test 3.3.2 {
  sqlite3_snapshot_free $snapshot
  execsql COMMIT
} {}

#-------------------------------------------------------------------------
# Check that SQLITE_BUSY_SNAPSHOT is returned if the specified snapshot
# no longer exists because the wal file has been checkpointed.
#
#   1. Reading a snapshot from the middle of a wal file is not possible
#      after the wal file has been checkpointed.
#
#   2. That a snapshot from the end of a wal file can not be read once
#      the wal file has been wrapped.
#
do_execsql_test 4.1.0 {
  PRAGMA journal_mode = wal;
  CREATE TABLE t3(i, j);
  INSERT INTO t3 VALUES('o', 't');
  INSERT INTO t3 VALUES('t', 'f');
  BEGIN;
    SELECT * FROM t3;
} {wal o t t f}

do_test 4.1.1 {
  set snapshot [sqlite3_snapshot_get db main]
  execsql COMMIT
} {}
do_test 4.1.2 {
  execsql { 
    INSERT INTO t3 VALUES('f', 's'); 
    BEGIN;
  }
  sqlite3_snapshot_open db main $snapshot
  execsql { SELECT * FROM t3 }
} {o t t f}

do_test 4.1.3 {
  execsql { 
    COMMIT;
    PRAGMA wal_checkpoint;
    BEGIN;
  }
  list [catch {sqlite3_snapshot_open db main $snapshot} msg] $msg
} {1 SQLITE_BUSY_SNAPSHOT}
do_test 4.1.4 {
  sqlite3_snapshot_free $snapshot
  execsql COMMIT
} {}

do_test 4.2.1 {
  execsql {
    INSERT INTO t3 VALUES('s', 'e');
    INSERT INTO t3 VALUES('n', 't');
    BEGIN;
      SELECT * FROM t3;
  }
} {o t t f f s s e n t}
do_test 4.2.2 {
  set snapshot [sqlite3_snapshot_get db main]
  execsql {
    COMMIT;
    PRAGMA wal_checkpoint;
    BEGIN;
  }
  sqlite3_snapshot_open db main $snapshot
  execsql { SELECT * FROM t3 }
} {o t t f f s s e n t}
do_test 4.2.3 {
  execsql {
    COMMIT;
    INSERT INTO t3 VALUES('e', 't');
    BEGIN;
  }
  list [catch {sqlite3_snapshot_open db main $snapshot} msg] $msg
} {1 SQLITE_BUSY_SNAPSHOT}
do_test 4.2.4 {
  sqlite3_snapshot_free $snapshot
} {}

#-------------------------------------------------------------------------
# Check that SQLITE_BUSY is returned if a checkpoint is running when
# sqlite3_snapshot_open() is called.
#
reset_db
db close
testvfs tvfs
sqlite3 db test.db -vfs tvfs

do_execsql_test 5.1 {
  PRAGMA journal_mode = wal;
  CREATE TABLE x1(x, xx, xxx);
  INSERT INTO x1 VALUES('z', 'zz', 'zzz');
  BEGIN;
    SELECT * FROM x1;
} {wal z zz zzz}

do_test 5.2 {
  set ::snapshot [sqlite3_snapshot_get db main]
  sqlite3 db2 test.db -vfs tvfs
  execsql {
    INSERT INTO x1 VALUES('a', 'aa', 'aaa');
    COMMIT;
  }
} {}

set t53 0
proc write_callback {args} {
  do_test 5.3.[incr ::t53] {
    execsql BEGIN
    list [catch { sqlite3_snapshot_open db main $::snapshot } msg] $msg
  } {1 SQLITE_BUSY}
  catchsql COMMIT
}

tvfs filter xWrite
tvfs script write_callback
db2 eval { PRAGMA wal_checkpoint }
db close
db2 close
tvfs delete
sqlite3_snapshot_free $snapshot

#-------------------------------------------------------------------------
# Test that sqlite3_snapshot_get() may be called immediately after
# "BEGIN; PRAGMA user_version;". And that sqlite3_snapshot_open() may
# be called after opening the db handle and running the script
# "PRAGMA user_version; BEGIN".
reset_db
do_execsql_test 6.1 {
  PRAGMA journal_mode = wal;
  CREATE TABLE x1(x, xx, xxx);
  INSERT INTO x1 VALUES('z', 'zz', 'zzz');
  BEGIN;
    PRAGMA user_version;
} {wal 0}
do_test 6.2 {
  set ::snapshot [sqlite3_snapshot_get db main]
  execsql {
    INSERT INTO x1 VALUES('a', 'aa', 'aaa');
    COMMIT;
  }
} {}
do_test 6.3 {
  sqlite3 db2 test.db 
  db2 eval "PRAGMA user_version ; BEGIN"
  sqlite3_snapshot_open db2 main $::snapshot
  db2 eval { SELECT * FROM x1 }
} {z zz zzz}
do_test 6.4 {
  db2 close
  sqlite3 db2 test.db 
  db2 eval "PRAGMA application_id"
  db2 eval "BEGIN"
  sqlite3_snapshot_open db2 main $::snapshot
  db2 eval { SELECT * FROM x1 }
} {z zz zzz}

do_test 6.5 {
  db2 close
  sqlite3 db2 test.db 
  db2 eval "BEGIN"
  list [catch {sqlite3_snapshot_open db2 main $::snapshot} msg] $msg
} {1 SQLITE_ERROR}

sqlite3_snapshot_free $snapshot

#-------------------------------------------------------------------------
# The following tests investigate the sqlite3_snapshot_cmp() API.
#

# Compare snapshots $p1 and $p2, checking that the result is $r.
#
proc do_snapshot_cmp_test {tn p1 p2 r} {
  uplevel [list do_test $tn.1 [list sqlite3_snapshot_cmp $p1 $p2] $r]
  uplevel [list do_test $tn.2 [list sqlite3_snapshot_cmp $p2 $p1] [expr $r*-1]]
  uplevel [list do_test $tn.3 [list sqlite3_snapshot_cmp $p1 $p1] 0]
  uplevel [list do_test $tn.4 [list sqlite3_snapshot_cmp $p2 $p2] 0]
}

catch { db2 close }
reset_db

do_execsql_test 7.1 {
  PRAGMA journal_mode = wal;
  CREATE TABLE t1(x);
} wal

do_test 7.1.2 {
  execsql { BEGIN ; PRAGMA application_id }
  set p1 [sqlite3_snapshot_get db main]
  execsql {
    INSERT INTO t1 VALUES(10);
    COMMIT;
  }
  execsql { BEGIN ; PRAGMA application_id }
  set p2 [sqlite3_snapshot_get db main]
  execsql COMMIT
} {}

do_snapshot_cmp_test 7.1.3 $p1 $p2 -1
sqlite3_snapshot_free $p1
sqlite3_snapshot_free $p2

do_execsql_test 7.2.1 {
  INSERT INTO t1 VALUES(11);
  INSERT INTO t1 VALUES(12);
  INSERT INTO t1 VALUES(13);
  BEGIN; 
    PRAGMA application_id;
} {0}
do_test 7.2.2 {
  set p1 [sqlite3_snapshot_get db main]
  execsql {
    COMMIT;
    INSERT INTO t1 VALUES(14);
    PRAGMA wal_checkpoint;
    BEGIN;
      PRAGMA application_id;
  }
  set p2 [sqlite3_snapshot_get db main]
  execsql COMMIT
} {}

do_snapshot_cmp_test 7.2.3 $p1 $p2 -1
sqlite3_snapshot_free $p2

do_test 7.3.1 {
  execsql {
    INSERT INTO t1 VALUES(14);
    BEGIN;
      PRAGMA application_id;
  }
  set p2 [sqlite3_snapshot_get db main]
  execsql COMMIT
} {}

do_snapshot_cmp_test 7.3.2 $p1 $p2 -1
sqlite3_snapshot_free $p1
sqlite3_snapshot_free $p2


finish_test

# is that each connection opened as part of this permutation executes
# "PRAGMA journal_mode=memory", which fails if the database is in wal mode
# and there are one or more existing connections.
if {[permutation]=="inmemory_journal"} {
  finish_test
  return
}

foreach {tn tcl} {
  1 {
    proc snapshot_get {DB DBNAME} {
      uplevel [list sqlite3_snapshot_get $DB $DBNAME]
    }
    proc snapshot_open {DB DBNAME SNAPSHOT} {
      uplevel [list sqlite3_snapshot_open $DB $DBNAME $SNAPSHOT]
    }
    proc snapshot_free {SNAPSHOT} {
      uplevel [list sqlite3_snapshot_free $SNAPSHOT]
    }
    proc snapshot_cmp {SNAPSHOT1 SNAPSHOT2} {
      uplevel [list sqlite3_snapshot_cmp $SNAPSHOT1 $SNAPSHOT2]
    }
  }

  2 {
    proc snapshot_get {DB DBNAME} {
      uplevel [list sqlite3_snapshot_get_blob $DB $DBNAME]
    }
    proc snapshot_open {DB DBNAME SNAPSHOT} {
      uplevel [list sqlite3_snapshot_open_blob $DB $DBNAME $SNAPSHOT]
    }
    proc snapshot_free {SNAPSHOT} {
    }
    proc snapshot_cmp {SNAPSHOT1 SNAPSHOT2} {
      uplevel [list sqlite3_snapshot_cmp_blob $SNAPSHOT1 $SNAPSHOT2]
    }
  }
} {

  reset_db
  eval $tcl

  #-------------------------------------------------------------------------
  # Check some error conditions in snapshot_get(). It is an error if:
  #
  #  1) snapshot_get() is called on a non-WAL database, or
  #  2) there is an open write transaction on the database.
  #
  do_execsql_test $tn.1.0 {
    CREATE TABLE t1(a, b);
    INSERT INTO t1 VALUES(1, 2);
    INSERT INTO t1 VALUES(3, 4);
  }

  do_test $tn.1.1.1 {
    execsql { BEGIN; SELECT * FROM t1; }
    list [catch { snapshot_get db main } msg] $msg
  } {1 SQLITE_ERROR}
  do_execsql_test 1.1.2 COMMIT

  do_test $tn.1.2.1 {
    execsql {
      PRAGMA journal_mode = WAL;
      BEGIN;
        INSERT INTO t1 VALUES(5, 6);
        INSERT INTO t1 VALUES(7, 8);
    }
    list [catch { snapshot_get db main } msg] $msg
  } {1 SQLITE_ERROR}
  do_execsql_test $tn.1.3.2 COMMIT

  #-------------------------------------------------------------------------
  # Check that a simple case works. Reuse the database created by the
  # block of tests above.
  #
  do_execsql_test $tn.2.1.0 {
    BEGIN;
      SELECT * FROM t1;
  } {1 2 3 4 5 6 7 8}

  do_test $tn.2.1.1 {
    set snapshot [snapshot_get db main]
    execsql {
      COMMIT;
      INSERT INTO t1 VALUES(9, 10);
      SELECT * FROM t1;
    }
  } {1 2 3 4 5 6 7 8 9 10}

  do_test $tn.2.1.2 {
    execsql BEGIN
    snapshot_open db main $snapshot
    execsql {
      SELECT * FROM t1;
    }
  } {1 2 3 4 5 6 7 8}

  do_test $tn.2.1.3 {
    snapshot_free $snapshot
    execsql COMMIT
  } {}

  do_test $tn.2.2.0 {
    sqlite3 db2 test.db
    execsql {
      BEGIN;
        SELECT * FROM t1;
    } db2
  } {1 2 3 4 5 6 7 8 9 10}

  do_test $tn.2.2.1 {
    set snapshot [snapshot_get db2 main]
    execsql {
      INSERT INTO t1 VALUES(11, 12);
      SELECT * FROM t1;
    }
  } {1 2 3 4 5 6 7 8 9 10 11 12}

  do_test $tn.2.2.2 {
    execsql BEGIN
    snapshot_open db main $snapshot
    execsql {
      SELECT * FROM t1;
    }
  } {1 2 3 4 5 6 7 8 9 10}

  do_test $tn.2.2.3 {
    snapshot_free $snapshot
    execsql COMMIT
    execsql COMMIT db2
    db2 close
  } {}

  do_test $tn.2.3.1 {
    execsql { DELETE FROM t1 WHERE a>6 }
    set snapshot [snapshot_get db main]
    execsql {
      INSERT INTO t1 VALUES('a', 'b');
      INSERT INTO t1 VALUES('c', 'd');
      SELECT * FROM t1;
    }
  } {1 2 3 4 5 6 a b c d}
  do_test $tn.2.3.2 {
    execsql BEGIN
    snapshot_open db main $snapshot
    execsql { SELECT * FROM t1 }
  } {1 2 3 4 5 6}

  do_test $tn.2.3.3 {
    catchsql {
      INSERT INTO t1 VALUES('x','y')
    }
  } {1 {database is locked}}
  do_test $tn.2.3.4 {
    execsql COMMIT
    snapshot_free $snapshot
  } {}

  #-------------------------------------------------------------------------
  # Check some errors in snapshot_open(). It is an error if:
  #
  #   1) the db is in auto-commit mode,
  #   2) the db has an open (read or write) transaction,
  #   3) the db is not a wal database,
  #
  # Reuse the database created by earlier tests.
  #
  do_execsql_test $tn.3.0.0 {
    CREATE TABLE t2(x, y);
    INSERT INTO t2 VALUES('a', 'b');
    INSERT INTO t2 VALUES('c', 'd');
    BEGIN;
      SELECT * FROM t2;
  } {a b c d}
  do_test $tn.3.0.1 {
    set snapshot [snapshot_get db main]
    execsql { COMMIT }
    execsql { INSERT INTO t2 VALUES('e', 'f'); }
  } {}

  do_test $tn.3.1 {
    list [catch {snapshot_open db main $snapshot } msg] $msg
  } {1 SQLITE_ERROR}

  do_test $tn.3.2.1 {
    execsql {
      BEGIN;
        SELECT * FROM t2;
    }
  } {a b c d e f}
  do_test $tn.3.2.2 {
    list [catch {snapshot_open db main $snapshot } msg] $msg
  } {1 SQLITE_ERROR}

  do_test $tn.3.2.3 {
    execsql {
      COMMIT;
      BEGIN;
        INSERT INTO t2 VALUES('g', 'h');
    }
    list [catch {snapshot_open db main $snapshot } msg] $msg
  } {1 SQLITE_ERROR}
  do_execsql_test 3.2.4 COMMIT

  do_test $tn.3.3.1 {
    execsql { PRAGMA journal_mode = DELETE }
    execsql { BEGIN }
    list [catch {snapshot_open db main $snapshot } msg] $msg
  } {1 SQLITE_ERROR}

  do_test $tn.$tn.3.3.2 {
    snapshot_free $snapshot
    execsql COMMIT
  } {}

  #-------------------------------------------------------------------------
  # Check that SQLITE_BUSY_SNAPSHOT is returned if the specified snapshot
  # no longer exists because the wal file has been checkpointed.
  #
  #   1. Reading a snapshot from the middle of a wal file is not possible
  #      after the wal file has been checkpointed.
  #
  #   2. That a snapshot from the end of a wal file can not be read once
  #      the wal file has been wrapped.
  #
  do_execsql_test $tn.4.1.0 {
    PRAGMA journal_mode = wal;
    CREATE TABLE t3(i, j);
    INSERT INTO t3 VALUES('o', 't');
    INSERT INTO t3 VALUES('t', 'f');
    BEGIN;
      SELECT * FROM t3;
  } {wal o t t f}

  do_test $tn.4.1.1 {
    set snapshot [snapshot_get db main]
    execsql COMMIT
  } {}
  do_test $tn.4.1.2 {
    execsql { 
      INSERT INTO t3 VALUES('f', 's'); 
      BEGIN;
    }
    snapshot_open db main $snapshot
    execsql { SELECT * FROM t3 }
  } {o t t f}

  do_test $tn.4.1.3 {
    execsql { 
      COMMIT;
      PRAGMA wal_checkpoint;
      BEGIN;
    }
    list [catch {snapshot_open db main $snapshot} msg] $msg
  } {1 SQLITE_BUSY_SNAPSHOT}
  do_test $tn.4.1.4 {
    snapshot_free $snapshot
    execsql COMMIT
  } {}

  do_test $tn.4.2.1 {
    execsql {
      INSERT INTO t3 VALUES('s', 'e');
      INSERT INTO t3 VALUES('n', 't');
      BEGIN;
        SELECT * FROM t3;
    }
  } {o t t f f s s e n t}
  do_test $tn.4.2.2 {
    set snapshot [snapshot_get db main]
    execsql {
      COMMIT;
      PRAGMA wal_checkpoint;
      BEGIN;
    }
    snapshot_open db main $snapshot
    execsql { SELECT * FROM t3 }
  } {o t t f f s s e n t}
  do_test $tn.4.2.3 {
    execsql {
      COMMIT;
      INSERT INTO t3 VALUES('e', 't');
      BEGIN;
    }
    list [catch {snapshot_open db main $snapshot} msg] $msg
  } {1 SQLITE_BUSY_SNAPSHOT}
  do_test $tn.4.2.4 {
    snapshot_free $snapshot
  } {}

  #-------------------------------------------------------------------------
  # Check that SQLITE_BUSY is returned if a checkpoint is running when
  # sqlite3_snapshot_open() is called.
  #
  reset_db
  db close
  testvfs tvfs
  sqlite3 db test.db -vfs tvfs

  do_execsql_test $tn.5.1 {
    PRAGMA journal_mode = wal;
    CREATE TABLE x1(x, xx, xxx);
    INSERT INTO x1 VALUES('z', 'zz', 'zzz');
    BEGIN;
      SELECT * FROM x1;
  } {wal z zz zzz}

  do_test $tn.5.2 {
    set ::snapshot [snapshot_get db main]
    sqlite3 db2 test.db -vfs tvfs
    execsql {
      INSERT INTO x1 VALUES('a', 'aa', 'aaa');
      COMMIT;
    }
  } {}

  set t53 0
  proc write_callback {args} {
    do_test $tn.5.3.[incr ::t53] {
      execsql BEGIN
      list [catch { snapshot_open db main $::snapshot } msg] $msg
    } {1 SQLITE_BUSY}
    catchsql COMMIT
  }

  tvfs filter xWrite
  tvfs script write_callback
  db2 eval { PRAGMA wal_checkpoint }
  db close
  db2 close
  tvfs delete
  snapshot_free $snapshot

  #-------------------------------------------------------------------------
  # Test that sqlite3_snapshot_get() may be called immediately after
  # "BEGIN; PRAGMA user_version;". And that sqlite3_snapshot_open() may
  # be called after opening the db handle and running the script
  # "PRAGMA user_version; BEGIN".
  reset_db
  do_execsql_test $tn.6.1 {
    PRAGMA journal_mode = wal;
    CREATE TABLE x1(x, xx, xxx);
    INSERT INTO x1 VALUES('z', 'zz', 'zzz');
    BEGIN;
      PRAGMA user_version;
  } {wal 0}
  do_test $tn.6.2 {
    set ::snapshot [snapshot_get db main]
    execsql {
      INSERT INTO x1 VALUES('a', 'aa', 'aaa');
      COMMIT;
    }
  } {}
  do_test $tn.6.3 {
    sqlite3 db2 test.db 
    db2 eval "PRAGMA user_version ; BEGIN"
    snapshot_open db2 main $::snapshot
    db2 eval { SELECT * FROM x1 }
  } {z zz zzz}
  do_test $tn.6.4 {
    db2 close
    sqlite3 db2 test.db 
    db2 eval "PRAGMA application_id"
    db2 eval "BEGIN"
    snapshot_open db2 main $::snapshot
    db2 eval { SELECT * FROM x1 }
  } {z zz zzz}

  do_test $tn.6.5 {
    db2 close
    sqlite3 db2 test.db 
    db2 eval "BEGIN"
    list [catch {snapshot_open db2 main $::snapshot} msg] $msg
  } {1 SQLITE_ERROR}

  snapshot_free $snapshot

  #-------------------------------------------------------------------------
  # The following tests investigate the sqlite3_snapshot_cmp() API.
  #

  # Compare snapshots $p1 and $p2, checking that the result is $r.
  #
  proc do_snapshot_cmp_test {tn p1 p2 r} {
    uplevel [list do_test $tn.1 [list snapshot_cmp $p1 $p2] $r]
    uplevel [list do_test $tn.2 [list snapshot_cmp $p2 $p1] [expr $r*-1]]
    uplevel [list do_test $tn.3 [list snapshot_cmp $p1 $p1] 0]
    uplevel [list do_test $tn.4 [list snapshot_cmp $p2 $p2] 0]
  }

  catch { db2 close }
  reset_db

  do_execsql_test $tn.7.1 {
    PRAGMA journal_mode = wal;
    CREATE TABLE t1(x);
  } wal

  do_test $tn.7.1.2 {
    execsql { BEGIN ; PRAGMA application_id }
    set p1 [snapshot_get db main]
    execsql {
      INSERT INTO t1 VALUES(10);
      COMMIT;
    }
    execsql { BEGIN ; PRAGMA application_id }
    set p2 [snapshot_get db main]
    execsql COMMIT
  } {}

  do_snapshot_cmp_test $tn.7.1.3 $p1 $p2 -1
  snapshot_free $p1
  snapshot_free $p2

  do_execsql_test $tn.7.2.1 {
    INSERT INTO t1 VALUES(11);
    INSERT INTO t1 VALUES(12);
    INSERT INTO t1 VALUES(13);
    BEGIN; 
      PRAGMA application_id;
  } {0}
  do_test $tn.7.2.2 {
    set p1 [snapshot_get db main]
    execsql {
      COMMIT;
      INSERT INTO t1 VALUES(14);
      PRAGMA wal_checkpoint;
      BEGIN;
        PRAGMA application_id;
    }
    set p2 [snapshot_get db main]
    execsql COMMIT
  } {}

  do_snapshot_cmp_test $tn.7.2.3 $p1 $p2 -1
  snapshot_free $p2

  do_test $tn.7.3.1 {
    execsql {
      INSERT INTO t1 VALUES(14);
      BEGIN;
        PRAGMA application_id;
    }
    set p2 [snapshot_get db main]
    execsql COMMIT
  } {}

  do_snapshot_cmp_test $tn.7.3.2 $p1 $p2 -1
  snapshot_free $p1
  snapshot_free $p2
}

finish_test