int maxStmt;               /* The next maximum number of stmtList */
  int nStmt;                 /* Number of statements in stmtList */
  IncrblobChannel *pIncrblob;/* Linked list of open incrblob channels */
  int nStep, nSort, nIndex;  /* Statistics for most recent operation */
  int nVMStep;               /* Another statistic for most recent operation */
  int nTransaction;          /* Number of nested [transaction] methods */
  int openFlags;             /* Flags used to open.  (SQLITE_OPEN_URI) */
  unsigned int modeFlags;    /* Operating mode flags */
#ifdef SQLITE_TEST
  int bLegacyPrepare;        /* True to use sqlite3_prepare() */
#endif
};

/*
** Valid values for SqliteDb.modeFlags
*/
#define SQLITE_TCLMODE_UNSETNULL  0x0001  /* Unset NULL array values in */
                                          /*   db eval ARRAY SQL */

struct IncrblobChannel {
  sqlite3_blob *pBlob;      /* sqlite3 blob handle */
  SqliteDb *pDb;            /* Associated database connection */
  int iSeek;                /* Current seek offset */
  Tcl_Channel channel;      /* Channel identifier */
  IncrblobChannel *pNext;   /* Linked list of all open incrblob channels */
  IncrblobChannel *pPrev;   /* Linked list of all open incrblob channels */

  while( (rc==TCL_OK || rc==TCL_CONTINUE) && TCL_OK==(rc = dbEvalStep(p)) ){
    int i;
    int nCol;
    Tcl_Obj **apColName;
    dbEvalRowInfo(p, &nCol, &apColName);
    for(i=0; i<nCol; i++){

      if( pArray==0 ){
        Tcl_ObjSetVar2(interp, apColName[i], 0, dbEvalColumnValue(p,i), 0);
      }else if( (p->pDb->modeFlags & SQLITE_TCLMODE_UNSETNULL)!=0
             && sqlite3_column_type(p->pPreStmt->pStmt, i)==SQLITE_NULL 
      ){
        Tcl_UnsetVar2(interp, Tcl_GetString(pArray), 
                      Tcl_GetString(apColName[i]), 0);
      }else{
        Tcl_ObjSetVar2(interp, pArray, apColName[i], dbEvalColumnValue(p,i), 0);
      }
    }

    /* The required interpreter variables are now populated with the data
    ** from the current row. If using NRE, schedule callbacks to evaluate
    ** script pScript, then to invoke this function again to fetch the next
    ** row (or clean up if there is no next row or the script throws an

  SqliteDb *p;
  const char *zArg;
  char *zErrMsg;
  int i;
  const char *zFile;
  const char *zVfs = 0;
  int flags;
  unsigned int modeFlags = 0;
  Tcl_DString translatedFilename;
#if defined(SQLITE_HAS_CODEC) && !defined(SQLITE_OMIT_CODEC_FROM_TCL)
  void *pKey = 0;
  int nKey = 0;
#endif
  int rc;

      int b;
      if( Tcl_GetBooleanFromObj(interp, objv[i+1], &b) ) return TCL_ERROR;
      if( b ){
        flags |= SQLITE_OPEN_URI;
      }else{
        flags &= ~SQLITE_OPEN_URI;
      }
    }else if( strcmp(zArg, "-unsetnull")==0 ){
      int b;
      if( Tcl_GetBooleanFromObj(interp, objv[i+1], &b) ) return TCL_ERROR;
      if( b ){
        modeFlags |= SQLITE_TCLMODE_UNSETNULL;
      }else{
        modeFlags &= ~SQLITE_TCLMODE_UNSETNULL;
      }
    }else{
      Tcl_AppendResult(interp, "unknown option: ", zArg, (char*)0);
      return TCL_ERROR;
    }
  }
  if( objc<3 || (objc&1)!=1 ){
    Tcl_WrongNumArgs(interp, 1, objv,
      "HANDLE FILENAME ?-vfs VFSNAME? ?-readonly BOOLEAN? ?-create BOOLEAN?"
      " ?-nomutex BOOLEAN? ?-fullmutex BOOLEAN? ?-uri BOOLEAN?"
      " ?-unsetnull BOOLEAN?"
#if defined(SQLITE_HAS_CODEC) && !defined(SQLITE_OMIT_CODEC_FROM_TCL)
      " ?-key CODECKEY?"
#endif
    );
    return TCL_ERROR;
  }
  zErrMsg = 0;

    Tcl_SetResult(interp, zErrMsg, TCL_VOLATILE);
    Tcl_Free((char*)p);
    sqlite3_free(zErrMsg);
    return TCL_ERROR;
  }
  p->maxStmt = NUM_PREPARED_STMTS;
  p->openFlags = flags & SQLITE_OPEN_URI;
  p->modeFlags = modeFlags;
  p->interp = interp;
  zArg = Tcl_GetStringFromObj(objv[1], 0);
  if( DbUseNre() ){
    Tcl_NRCreateCommand(interp, zArg, DbObjCmdAdaptor, DbObjCmd,
                        (char*)p, DbDeleteCmd);
  }else{
    Tcl_CreateObjCommand(interp, zArg, DbObjCmd, (char*)p, DbDeleteCmd);

# $Id: tclsqlite.test,v 1.73 2009/03/16 13:19:36 danielk1977 Exp $

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

# Check the error messages generated by tclsqlite
#
set r "sqlite_orig HANDLE FILENAME ?-vfs VFSNAME? ?-readonly BOOLEAN? ?-create BOOLEAN? ?-nomutex BOOLEAN? ?-fullmutex BOOLEAN? ?-uri BOOLEAN? ?-unsetnull BOOLEAN?"
if {[sqlite3 -has-codec]} {
  append r " ?-key CODECKEY?"
}
do_test tcl-1.1 {
  set v [catch {sqlite3 bogus} msg]
  regsub {really_sqlite3} $msg {sqlite3} msg
  lappend v $msg

do_test tcl-15.4 {
  db exists {SELECT a FROM t1 WHERE a>2}
} {1}
do_test tcl-15.5 {
  db exists {SELECT a FROM t1 WHERE a>3}
} {0}

# 2017-06-26: Different behavior with "-unsetnull 1" versus "-unsetnull 0"
#
# In the "db eval SQL ARRAY" form, NULL results cause the corresponding
# array entry to be unset with -unsetnull 1.  With -unsetnull 0, the NULL
# results cause the array entry to be filled with the [db nullvalue] string.
# The -unsetnull 0 version is the default, for legacy compatibility.
#
catch {db close}
forcedelete test.db
sqlite3 db test.db
do_execsql_test tcl-16.100 {
  CREATE TABLE t1(a,b);
  INSERT INTO t1 VALUES(1,2),(2,NULL),(3,'xyz');
}
do_test tcl-16.101 {
  set res {}
  unset -nocomplain x
  db eval {SELECT * FROM t1} x {
    lappend res $x(a) [array names x]
  }
  set res
} {1 {a b *} 2 {a b *} 3 {a b *}}
sqlite3 db test.db -unsetnull 0
do_test tcl-16.102 {
  set res {}
  unset -nocomplain x
  db eval {SELECT * FROM t1} x {
    lappend res $x(a) [array names x]
  }
  set res
} {1 {a b *} 2 {a b *} 3 {a b *}}
sqlite3 db test.db -unsetnull 1
do_test tcl-16.103 {
  set res {}
  unset -nocomplain x
  db eval {SELECT * FROM t1} x {
    lappend res $x(a) [array names x]
  }
  set res
} {1 {a b *} 2 {a *} 3 {a b *}}

finish_test