** in pParse->zErr (system tables may not be altered) and returns non-zero.
**
** Or, if zName is not a system table, zero is returned.
*/
static int isAlterableTable(Parse *pParse, Table *pTab){
  if( 0==sqlite3StrNICmp(pTab->zName, "sqlite_", 7) 
#ifndef SQLITE_OMIT_VIRTUALTABLE
   || ( (pTab->tabFlags & TF_Shadow)!=0

        && sqlite3ReadOnlyShadowTables(pParse->db)
   )
#endif
  ){
    sqlite3ErrorMsg(pParse, "table %s may not be altered", pTab->zName);
    return 1;
  }
  return 0;

    ){
      if( sqlite3Config.bExtraSchemaChecks ){
        sqlite3ErrorMsg(pParse, ""); /* corruptSchema() will supply the error */
        return SQLITE_ERROR;
      }
    }
  }else{

    if( (pParse->nested==0 && 0==sqlite3StrNICmp(zName, "sqlite_", 7))
     || (sqlite3ReadOnlyShadowTables(db) && sqlite3ShadowTableName(db, zName))
    ){
      sqlite3ErrorMsg(pParse, "object name reserved for internal use: %s",
                      zName);
      return SQLITE_ERROR;
    }

  }
  return SQLITE_OK;
}

/*
** Return the PRIMARY KEY index of a table
*/

/*
** Return true if zName is a shadow table name in the current database
** connection.
**
** zName is temporarily modified while this routine is running, but is
** restored to its original value prior to this routine returning.
*/
int sqlite3ShadowTableName(sqlite3 *db, const char *zName){
  char *zTail;                  /* Pointer to the last "_" in zName */
  Table *pTab;                  /* Table that zName is a shadow of */
  Module *pMod;                 /* Module for the virtual table */

  zTail = strrchr(zName, '_');
  if( zTail==0 ) return 0;
  *zTail = 0;
  pTab = sqlite3FindTable(db, zName, 0);
  *zTail = '_';
  if( pTab==0 ) return 0;
  if( !IsVirtual(pTab) ) return 0;
  pMod = (Module*)sqlite3HashFind(&db->aModule, pTab->azModuleArg[0]);
  if( pMod==0 ) return 0;
  if( pMod->pModule->iVersion<3 ) return 0;
  if( pMod->pModule->xShadowName==0 ) return 0;
  return pMod->pModule->xShadowName(zTail+1);
}


#endif /* ifndef SQLITE_OMIT_VIRTUALTABLE */

/*
** This routine is called to report the final ")" that terminates
** a CREATE TABLE statement.
**
** The table structure that other action routines have been building

  if( pEnd==0 && pSelect==0 ){
    return;
  }
  assert( !db->mallocFailed );
  p = pParse->pNewTable;
  if( p==0 ) return;

  if( pSelect==0 && sqlite3ShadowTableName(db, p->zName) ){
    p->tabFlags |= TF_Shadow;
  }

  /* If the db->init.busy is 1 it means we are reading the SQL off the
  ** "sqlite_master" or "sqlite_temp_master" table on the disk.
  ** So do not write to the disk again.  Extract the root page number
  ** for the table from the db->init.newTnum field.  (The page number

    sqlite3VdbeAddOp4(v, OP_VDestroy, iDb, 0, 0, pTab->zName, 0);
    sqlite3MayAbort(pParse);
  }
  sqlite3VdbeAddOp4(v, OP_DropTable, iDb, 0, 0, pTab->zName, 0);
  sqlite3ChangeCookie(pParse, iDb);
  sqliteViewResetAll(db, iDb);
}

/*
** Return TRUE if shadow tables should be read-only in the current
** context.
*/
int sqlite3ReadOnlyShadowTables(sqlite3 *db){
#ifndef SQLITE_OMIT_VIRTUALTABLE
  if( (db->flags & SQLITE_Defensive)!=0
   && db->pVtabCtx==0
   && db->nVdbeExec==0
  ){
    return 1;
  }
#endif
  return 0;
}

/*
** Return true if it is not allowed to drop the given table
*/
static int tableMayNotBeDropped(sqlite3 *db, Table *pTab){
  if( sqlite3StrNICmp(pTab->zName, "sqlite_", 7)==0 ){
    if( sqlite3StrNICmp(pTab->zName+7, "stat", 4)==0 ) return 0;
    if( sqlite3StrNICmp(pTab->zName+7, "parameters", 10)==0 ) return 0;
    return 1;
  }
  if( (pTab->tabFlags & TF_Shadow)!=0 && sqlite3ReadOnlyShadowTables(db) ){

    return 1;
  }
  return 0;
}

/*
** This routine is called to do the work of a DROP TABLE statement.
** pName is the name of the table to be dropped.

      goto exit_drop_table;
    }
    if( sqlite3AuthCheck(pParse, SQLITE_DELETE, pTab->zName, 0, zDb) ){
      goto exit_drop_table;
    }
  }
#endif
  if( tableMayNotBeDropped(db, pTab) ){
    sqlite3ErrorMsg(pParse, "table %s may not be dropped", pTab->zName);
    goto exit_drop_table;
  }

#ifndef SQLITE_OMIT_VIEW
  /* Ensure DROP TABLE is not used on a view, and DROP VIEW is not used
  ** on a table.

  }
  if( (pTab->tabFlags & (TF_Readonly|TF_Shadow))==0 ) return 0;
  db = pParse->db;
  if( (pTab->tabFlags & TF_Readonly)!=0 ){
    return sqlite3WritableSchema(db)==0 && pParse->nested==0;
  }
  assert( pTab->tabFlags & TF_Shadow );
  return sqlite3ReadOnlyShadowTables(db);




}

/*
** Check to make sure the given table is writable.  If it is not
** writable, generate an error message and return 1.  If it is
** writable return 0;
*/

     sqlite3*,
     const char*,
     const sqlite3_module*,
     void*,
     void(*)(void*)
   );
#  define sqlite3VtabInSync(db) ((db)->nVTrans>0 && (db)->aVTrans==0)
#endif
int sqlite3ReadOnlyShadowTables(sqlite3 *db);
#ifndef SQLITE_OMIT_VIRTUALTABLE
  int sqlite3ShadowTableName(sqlite3 *db, const char *zName);
#else
# define sqlite3ShadowTableName(A,B) 0
#endif
int sqlite3VtabEponymousTableInit(Parse*,Module*);
void sqlite3VtabEponymousTableClear(sqlite3*,Module*);
void sqlite3VtabMakeWritable(Parse*,Table*);
void sqlite3VtabBeginParse(Parse*, Token*, Token*, Token*, int);
void sqlite3VtabFinishParse(Parse*, Token*);
void sqlite3VtabArgInit(Parse*);

    CREATE VIRTUAL TABLE y1 USING fts3;
  }

  do_catchsql_test 16.10 {
    INSERT INTO y1_segments VALUES(1, X'1234567890');
  } {1 {table y1_segments may not be modified}}

  do_catchsql_test 16.20 {
    DROP TABLE y1_segments;
  } {1 {table y1_segments may not be dropped}}

  do_catchsql_test 16.20 {
    ALTER TABLE y1_segments RENAME TO abc;
  } {1 {table y1_segments may not be altered}}
  sqlite3_db_config db DEFENSIVE 0
  do_catchsql_test 16.22 {
    ALTER TABLE y1_segments RENAME TO abc;
  } {0 {}}
  sqlite3_db_config db DEFENSIVE 1
  do_catchsql_test 16.23 {
    CREATE TABLE y1_segments AS SELECT * FROM abc;
  } {1 {object name reserved for internal use: y1_segments}}
  do_catchsql_test 16.24 {
    CREATE VIEW y1_segments AS SELECT * FROM abc;
  } {1 {object name reserved for internal use: y1_segments}}
  sqlite3_db_config db DEFENSIVE 0
  do_catchsql_test 16.25 {
    ALTER TABLE abc RENAME TO y1_segments;
  } {0 {}}
  sqlite3_db_config db DEFENSIVE 1

  do_execsql_test 16.30 {
    ALTER TABLE y1 RENAME TO z1;
  }

  do_execsql_test 16.40 {
    SELECT * FROM z1_segments;