SQLite

      rc = SQLITE_OK;
    }else if( op==SQLITE_FCNTL_VFS_POINTER ){
      *(sqlite3_vfs**)pArg = sqlite3PagerVfs(pPager);
      rc = SQLITE_OK;
    }else if( op==SQLITE_FCNTL_JOURNAL_POINTER ){
      *(sqlite3_file**)pArg = sqlite3PagerJrnlFile(pPager);
      rc = SQLITE_OK;
    }else if( op==SQLITE_FCNTL_DATA_VERSION ){
      *(unsigned int*)pArg = sqlite3PagerDataVersion(pPager);
      rc = SQLITE_OK;
    }else{
      rc = sqlite3OsFileControl(fd, op, pArg);
    }
    sqlite3BtreeLeave(pBtree);
  }
  sqlite3_mutex_leave(db->mutex);
  return rc;

  sqlite3PcacheClear(pPager->pPCache);
}

/*
** Return the pPager->iDataVersion value
*/
u32 sqlite3PagerDataVersion(Pager *pPager){

  return pPager->iDataVersion;
}

/*
** Free all structures in the Pager.aSavepoint[] array and set both
** Pager.aSavepoint and Pager.nSavepoint to zero. Close the sub-journal
** if it is open and the pager is not in exclusive mode.

       "SELECT count(*) FROM %s WHERE type='trigger'" },
     { "number of views:",
       "SELECT count(*) FROM %s WHERE type='view'" },
     { "schema size:",
       "SELECT total(length(sql)) FROM %s" },
  };
  int i;
  unsigned iDataVersion;
  char *zSchemaTab;
  char *zDb = nArg>=2 ? azArg[1] : "main";
  sqlite3_stmt *pStmt = 0;
  unsigned char aHdr[100];
  open_db(p, 0);
  if( p->db==0 ) return 1;
  sqlite3_prepare_v2(p->db,"SELECT data FROM sqlite_dbpage(?1) WHERE pgno=1",

  for(i=0; i<ArraySize(aQuery); i++){
    char *zSql = sqlite3_mprintf(aQuery[i].zSql, zSchemaTab);
    int val = db_int(p, zSql);
    sqlite3_free(zSql);
    utf8_printf(p->out, "%-20s %d\n", aQuery[i].zName, val);
  }
  sqlite3_free(zSchemaTab);
  sqlite3_file_control(p->db, zDb, SQLITE_FCNTL_DATA_VERSION, &iDataVersion);
  utf8_printf(p->out, "%-20s %u\n", "data version", iDataVersion);
  return 0;
}

/*
** Print the current sqlite3_errmsg() value to stderr and return 1.
*/
static int shellDatabaseError(sqlite3 *db){

** a prior successful call to [SQLITE_FCNTL_BEGIN_ATOMIC_WRITE].
**
** <li>[[SQLITE_FCNTL_LOCK_TIMEOUT]]
** The [SQLITE_FCNTL_LOCK_TIMEOUT] opcode causes attempts to obtain
** a file lock using the xLock or xShmLock methods of the VFS to wait
** for up to M milliseconds before failing, where M is the single 
** unsigned integer parameter.
**
** <li>[[SQLITE_FCNTL_DATA_VERSION]]
** The [SQLITE_FCNTL_DATA_VERSION] opcode is used to detect changes to
** a database file.  The argument is a pointer to a 32-bit unsigned integer.
** The "data version" for the pager is written into the pointer.  The
** "data version" changes whenever any change occurs to the corresponding
** database file, either through SQL statements on the same database
** connection, or through transactions committed by separate database
** connections possibly in other processes. The [sqlite3_total_changes()]
** interface can be used to find if any database on the connection has changed,
** but that interface response to changes on TEMP as well as MAIN and does
** not provide a mechanism to detect changes to MAIN only.  Also, the
** [sqlite3_total_changes()] interface response to internal changes only and
** omits changes made by other database connections.  The
** [PRAGMA data_version] command provide a mechanism to detect changes to
** a single attached database that occur due to other database connections,
** but omits changes implemented by the database connection for which it is
** called.  This file control is the only mechanism to detect changes that
** happen either internally or externally on a single database.
** </ul>
*/
#define SQLITE_FCNTL_LOCKSTATE               1
#define SQLITE_FCNTL_GET_LOCKPROXYFILE       2
#define SQLITE_FCNTL_SET_LOCKPROXYFILE       3
#define SQLITE_FCNTL_LAST_ERRNO              4
#define SQLITE_FCNTL_SIZE_HINT               5

#define SQLITE_FCNTL_JOURNAL_POINTER        28
#define SQLITE_FCNTL_WIN32_GET_HANDLE       29
#define SQLITE_FCNTL_PDB                    30
#define SQLITE_FCNTL_BEGIN_ATOMIC_WRITE     31
#define SQLITE_FCNTL_COMMIT_ATOMIC_WRITE    32
#define SQLITE_FCNTL_ROLLBACK_ATOMIC_WRITE  33
#define SQLITE_FCNTL_LOCK_TIMEOUT           34
#define SQLITE_FCNTL_DATA_VERSION           35

/* deprecated names */
#define SQLITE_GET_LOCKPROXYFILE      SQLITE_FCNTL_GET_LOCKPROXYFILE
#define SQLITE_SET_LOCKPROXYFILE      SQLITE_FCNTL_SET_LOCKPROXYFILE
#define SQLITE_LAST_ERRNO             SQLITE_FCNTL_LAST_ERRNO

** part of trigger programs. ^Executing any other type of SQL statement
** does not affect the value returned by sqlite3_total_changes().
** 
** ^Changes made as part of [foreign key actions] are included in the
** count, but those made as part of REPLACE constraint resolution are
** not. ^Changes to a view that are intercepted by INSTEAD OF triggers 
** are not counted.
**
** This the [sqlite3_total_changes(D)] interface only reports the number
** of rows that changed due to SQL statement run against database
** connection D.  Any changes by other database connections are ignored.
** To detect changes against a database file from other database
** connections use the [PRAGMA data_version] command or the
** [SQLITE_FCNTL_DATA_VERSION] [file control].
** 
** If a separate thread makes changes on the same database connection
** while [sqlite3_total_changes()] is running then the value
** returned is unpredictable and not meaningful.
**
** See also:
** <ul>
** <li> the [sqlite3_changes()] interface
** <li> the [count_changes pragma]
** <li> the [changes() SQL function]
** <li> the [data_version pragma]
** <li> the [SQLITE_FCNTL_DATA_VERSION] [file control]
** </ul>
*/
int sqlite3_total_changes(sqlite3*);

/*
** CAPI3REF: Interrupt A Long-Running Query
** METHOD: sqlite3

** routine returns a NULL pointer.
*/
sqlite3_mutex *sqlite3_db_mutex(sqlite3*);

/*
** CAPI3REF: Low-Level Control Of Database Files
** METHOD: sqlite3
** KEYWORDS: {file control}
**
** ^The [sqlite3_file_control()] interface makes a direct call to the
** xFileControl method for the [sqlite3_io_methods] object associated
** with a particular database identified by the second argument. ^The
** name of the database is "main" for the main database or "temp" for the
** TEMP database, or the name that appears after the AS keyword for
** databases that are added using the [ATTACH] SQL command.
** ^A NULL pointer can be used in place of "main" to refer to the
** main database file.
** ^The third and fourth parameters to this routine
** are passed directly through to the second and third parameters of
** the xFileControl method.  ^The return value of the xFileControl
** method becomes the return value of this routine.
**
** A few opcodes for [sqlite3_file_control()] are handled directly
** by the SQLite core and never invoke the 
** sqlite3_io_methods.xFileControl method.
** ^The [SQLITE_FCNTL_FILE_POINTER] value for the op parameter causes
** a pointer to the underlying [sqlite3_file] object to be written into
** the space pointed to by the 4th parameter.  The

** [SQLITE_FCNTL_JOURNAL_POINTER] works similarly except that it returns
** the [sqlite3_file] object associated with the journal file instead of
** the main database.  The [SQLITE_FCNTL_VFS_POINTER] opcode returns
** a pointer to the underlying [sqlite3_vfs] object for the file.
** The [SQLITE_FCNTL_DATA_VERSION] returns the data version counter
** from the pager.
**
** ^If the second parameter (zDbName) does not match the name of any
** open database file, then SQLITE_ERROR is returned.  ^This error
** code is not remembered and will not be recalled by [sqlite3_errcode()]
** or [sqlite3_errmsg()].  The underlying xFileControl method might
** also return SQLITE_ERROR.  There is no way to distinguish between
** an incorrect zDbName and an SQLITE_ERROR return from the underlying

  if( iArg!=0 ) {
    Tcl_AppendResult(interp, "Unexpected non-zero errno: ",
                     Tcl_GetStringFromObj(Tcl_NewIntObj(iArg), 0), " ", 0);
    return TCL_ERROR;
  }
  return TCL_OK;  
}

/*
** tclcmd:   file_control_data_version DB DBNAME
**
** This TCL command runs the sqlite3_file_control with the
** SQLITE_FCNTL_DATA_VERSION opcode, returning the result.
*/
static int SQLITE_TCLAPI file_control_data_version(
  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int objc,              /* Number of arguments */
  Tcl_Obj *CONST objv[]  /* Command arguments */
){
  unsigned int iVers;             /* data version */
  char *zDb;                      /* Db name ("main", "temp" etc.) */
  sqlite3 *db;                    /* Database handle */
  int rc;                         /* file_control() return code */
  char zBuf[100];

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

  rc = sqlite3_file_control(db, zDb, SQLITE_FCNTL_DATA_VERSION, (void *)&iVers);
  if( rc ){
    Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
    return TCL_ERROR;
  }else{
    sqlite3_snprintf(sizeof(zBuf),zBuf,"%u",iVers);
    Tcl_SetResult(interp, (char *)zBuf, TCL_VOLATILE);
    return TCL_OK;
  }
}

/*
** tclcmd:   file_control_chunksize_test DB DBNAME SIZE
**
** This TCL command runs the sqlite3_file_control interface and
** verifies correct operation of the SQLITE_GET_LOCKPROXYFILE and
** SQLITE_SET_LOCKPROXYFILE verbs.

     { "vfs_unregister_all",         vfs_unregister_all,  0   },
     { "vfs_reregister_all",         vfs_reregister_all,  0   },
     { "file_control_test",          file_control_test,   0   },
     { "file_control_lasterrno_test", file_control_lasterrno_test,  0   },
     { "file_control_lockproxy_test", file_control_lockproxy_test,  0   },
     { "file_control_chunksize_test", file_control_chunksize_test,  0   },
     { "file_control_sizehint_test",  file_control_sizehint_test,   0   },
     { "file_control_data_version",   file_control_data_version,    0   },
#if SQLITE_OS_WIN
     { "file_control_win32_av_retry", file_control_win32_av_retry,  0   },
     { "file_control_win32_get_handle", file_control_win32_get_handle, 0  },
     { "file_control_win32_set_handle", file_control_win32_set_handle, 0  },
#endif
     { "file_control_persist_wal",    file_control_persist_wal,     0   },
     { "file_control_powersafe_overwrite",file_control_powersafe_overwrite,0},

# 2018-07-18
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
#
# Test case for SQLITE_FCNTL_DATA_VERSION
#

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

# Construct a database and get its initial data version
sqlite3 db test.db
do_test dataversion1-100 {
  db eval {
    CREATE TABLE t1(x);
    INSERT INTO t1(x) VALUES(99);
    SELECT * FROM t1;
  }
} {99}
set dv1 [file_control_data_version db main]

# The data version does not change by ATTACH or by changes to
# other schemas within the same connection.
#
do_test dataversion1-101 {
  db eval {
    ATTACH ':memory:' AS aux1;
    CREATE TABLE aux1.t2(y);
    CREATE TEMP TABLE t3(z);
  }
  file_control_data_version db main
} $dv1

# The data version does change when SQL modifies the table
do_test dataversion1-110 {
  db eval {
    UPDATE t1 SET x=x+1;
  }
  set dv2 [file_control_data_version db]
  expr {$::dv1==$dv2}
} {0}

# But the data version is constant if there are changes to other
# schemas
set dv1 [file_control_data_version db main]
do_test dataversion1-120 {
  db eval {
    UPDATE t2 SET y=y+1;
  }
  file_control_data_version db
} $dv1

# Changes to the database via another connection are not detected
# until there is a read transaction.
#
sqlite3 db2 test.db
do_test dataversion1-130 {
  db2 eval {
    SELECT * FROM t1
  }
} {100}
do_test dataversion1-131 {
  file_control_data_version db
} $dv1
do_test dataversion1-132 {
  db2 eval {
    UPDATE t1 SET x=x+1;
  }
  set dv2 [file_control_data_version db]
  expr {$::dv1==$dv2}
} {1}
do_test dataversion1-133 {
  db eval {SELECT * FROM t1}
  set dv2 [file_control_data_version db]
  expr {$::dv1==$dv2}
} {0}


   
finish_test