16 KiB
16 KiB
DatabaseReset
Resets a request, like after calling DatabasePrepare().
int DatabaseReset(
int request // request handle received in DatabasePrepare
);
Parameters
request
[in] The handle of the request obtained in DatabasePrepare().
Return Value
Return true if successful, otherwise false. To get the error code, use GetLastError(), the possible responses are:
- ERR_DATABASE_INVALID_HANDLE (5121) - invalid database handle;
- SQLite error codes starting with ERR_DATABASE_ERROR(5601).
Note
The DatabaseReset() function is intended for multiple execution of a request with different parameter values. For example, when adding data to the table in bulk using the INSERT command, a custom set of field values should be formed for each entry.
Unlike DatabasePrepare(), the DatabaseReset() call does not compile the string with SQL commands into a new request, therefore DatabaseReset() is executed much faster than DatabasePrepare().
DatabaseReset() is used together with the DatabaseBind() functions and/or DatabaseBindArray() if the request parameter values should be changed after executing DatabaseRead(). This means that before setting new values of the request parameters (before the block of DatabaseBind/DatabaseBindArray calls), DatabaseReset() should be called to reset it. The parametrized request itself should be created using DatabasePrepare().
Just like DatabasePrepare(), DatabaseReset() does not make a database request. A direct request execution is performed when calling DatabaseRead() or DatabaseReadBind().
DatabaseReset() call does not lead to resetting parameter values in the request if they were set by calling DatabaseBind()/DatabaseBindArray(), i.e. the parameters retain their values. Thus, the value of only a single parameter can be changed. There is no need to set all request parameters anew after calling DatabaseReset().
A handle of a request removed using DatabaseFinalize() cannot be passed to DatabaseReset(). This will result in an error.
Example:
//+------------------------------------------------------------------+
//| Script program start function |
//+------------------------------------------------------------------+
void OnStart()
{
//--- create or open a database
string filename="symbols.sqlite";
int db=DatabaseOpen(filename, DATABASE_OPEN_READWRITE | DATABASE_OPEN_CREATE);
if(db==INVALID_HANDLE)
{
Print("DB: ", filename, " open failed with code ", GetLastError());
return;
}
else
Print("Database: ", filename, " opened successfully");
//--- if the SYMBOLS table exists, delete it
if(DatabaseTableExists(db, "SYMBOLS"))
{
//--- delete the table
if(!DatabaseExecute(db, "DROP TABLE SYMBOLS"))
{
Print("Failed to drop table SYMBOLS with code ", GetLastError());
DatabaseClose(db);
return;
}
}
//--- create the SYMBOLS table
if(!DatabaseExecute(db, "CREATE TABLE SYMBOLS("
"NAME TEXT NOT NULL,"
"DESCRIPTION TEXT ,"
"PATH TEXT ,"
"SPREAD INT ,"
"POINT REAL NOT NULL,"
"DIGITS INT NOT NULL,"
"JSON BLOB );"))
{
Print("DB: ", filename, " create table failed with code ", GetLastError());
DatabaseClose(db);
return;
}
//--- display the list of all fields in the SYMBOLS table
if(DatabasePrint(db, "PRAGMA TABLE_INFO(SYMBOLS)", 0)<0)
{
PrintFormat("DatabasePrint(\"PRAGMA TABLE_INFO(SYMBOLS)\") failed, error code=%d at line %d", GetLastError(), __LINE__);
DatabaseClose(db);
return;
}
//--- create a parametrized request to add symbols to the SYMBOLS table
string sql="INSERT INTO SYMBOLS (NAME,DESCRIPTION,PATH,SPREAD,POINT,DIGITS,JSON)"
" VALUES (?1,?2,?3,?4,?5,?6,?7);"; // request parameters
int request=DatabasePrepare(db, sql);
if(request==INVALID_HANDLE)
{
PrintFormat("DatabasePrepare() failed with code=%d", GetLastError());
Print("SQL request: ", sql);
DatabaseClose(db);
return;
}
//--- go through all the symbols and add them to the SYMBOLS table
int symbols=SymbolsTotal(false);
bool request_error=false;
DatabaseTransactionBegin(db);
for(int i=0; i<symbols; i++)
{
//--- set the values of the parameters before adding a symbol
ResetLastError();
string symbol=SymbolName(i, false);
if(!DatabaseBind(request, 0, symbol))
{
PrintFormat("DatabaseBind() failed at line %d with code=%d", __LINE__, GetLastError());
request_error=true;
break;
}
//--- if the previous DatabaseBind() call was successful, set the next parameter
if(!DatabaseBind(request, 1, SymbolInfoString(symbol, SYMBOL_DESCRIPTION)))
{
PrintFormat("DatabaseBind() failed at line %d with code=%d", __LINE__, GetLastError());
request_error=true;
break;
}
if(!DatabaseBind(request, 2, SymbolInfoString(symbol, SYMBOL_PATH)))
{
PrintFormat("DatabaseBind() failed at line %d with code=%d", __LINE__, GetLastError());
request_error=true;
break;
}
if(!DatabaseBind(request, 3, SymbolInfoInteger(symbol, SYMBOL_SPREAD)))
{
PrintFormat("DatabaseBind() failed at line %d with code=%d", __LINE__, GetLastError());
request_error=true;
break;
}
if(!DatabaseBind(request, 4, SymbolInfoDouble(symbol, SYMBOL_POINT)))
{
PrintFormat("DatabaseBind() failed at line %d with code=%d", __LINE__, GetLastError());
request_error=true;
break;
}
if(!DatabaseBind(request, 5, SymbolInfoInteger(symbol, SYMBOL_DIGITS)))
{
PrintFormat("DatabaseBind() failed at line %d with code=%d", __LINE__, GetLastError());
request_error=true;
break;
}
if(!DatabaseBind(request, 6, GetSymBolAsJson(symbol)))
{
PrintFormat("DatabaseBind() failed at line %d with code=%d", __LINE__, GetLastError());
request_error=true;
break;
}
//--- execute a request for inserting the entry and check for an error
if(!DatabaseRead(request)&&(GetLastError()!=ERR_DATABASE_NO_MORE_DATA))
{
PrintFormat("DatabaseRead() failed with code=%d", GetLastError());
DatabaseFinalize(request);
request_error=true;
break;
}
else
PrintFormat("%d: added %s", i+1, symbol);
//--- reset the request before the next parameter update
if(!DatabaseReset(request))
{
PrintFormat("DatabaseReset() failed with code=%d", GetLastError());
DatabaseFinalize(request);
request_error=true;
break;
}
} //--- done going through all the symbols
//--- transactions status
if(request_error)
{
PrintFormat("Table SYMBOLS: failed to add %d symbols", symbols);
DatabaseTransactionRollback(db);
DatabaseClose(db);
return;
}
else
{
DatabaseTransactionCommit(db);
PrintFormat("Table SYMBOLS: added %d symbols",symbols);
}
//--- save the SYMBOLS table to a CSV file
string csv_filename="symbols.csv";
if(DatabaseExport(db, "SELECT * FROM SYMBOLS", csv_filename,
DATABASE_EXPORT_HEADER|DATABASE_EXPORT_INDEX|DATABASE_EXPORT_QUOTED_STRINGS, ";"))
Print("Database: table SYMBOLS saved in ", csv_filename);
else
Print("Database: DatabaseExport(\"SELECT * FROM SYMBOLS\") failed with code", GetLastError());
//--- close the database file and inform of that
DatabaseClose(db);
PrintFormat("Database: %s created and closed", filename);
}
//+------------------------------------------------------------------+
//| Return a symbol specification as JSON |
//+------------------------------------------------------------------+
string GetSymBolAsJson(string symbol)
{
//--- indents
string indent1=Indent(1);
string indent2=Indent(2);
string indent3=Indent(3);
//---
int digits=(int)SymbolInfoInteger(symbol, SYMBOL_DIGITS);
string json="{"+
"\n"+indent1+"\"ConfigSymbols\":["+
"\n"+indent2+"{"+
"\n"+indent3+"\"Symbol\":\""+symbol+"\","+
"\n"+indent3+"\"Path\":\""+SymbolInfoString(symbol, SYMBOL_PATH)+"\","+
"\n"+indent3+"\"CurrencyBase\":\""+SymbolInfoString(symbol, SYMBOL_CURRENCY_BASE)+"\","+
"\n"+indent3+"\"CurrencyProfit\":\""+SymbolInfoString(symbol, SYMBOL_CURRENCY_PROFIT)+"\","+
"\n"+indent3+"\"CurrencyMargin\":\""+SymbolInfoString(symbol, SYMBOL_CURRENCY_MARGIN)+"\","+
"\n"+indent3+"\"ColorBackground\":\""+ColorToString((color)SymbolInfoInteger(symbol, SYMBOL_BACKGROUND_COLOR))+"\","+
"\n"+indent3+"\"Digits\":\""+IntegerToString(SymbolInfoInteger(symbol, SYMBOL_DIGITS))+"\","+
"\n"+indent3+"\"Point\":\""+DoubleToString(SymbolInfoDouble(symbol, SYMBOL_POINT), digits)+"\","+
"\n"+indent3+"\"TickBookDepth\":\""+IntegerToString(SymbolInfoInteger(symbol, SYMBOL_TICKS_BOOKDEPTH))+"\","+
"\n"+indent3+"\"ChartMode\":\""+IntegerToString(SymbolInfoInteger(symbol, SYMBOL_CHART_MODE))+"\","+
"\n"+indent3+"\"TradeMode\":\""+IntegerToString(SymbolInfoInteger(symbol, SYMBOL_TRADE_EXEMODE))+"\","+
"\n"+indent3+"\"TradeCalcMode\":\""+IntegerToString(SymbolInfoInteger(symbol, SYMBOL_TRADE_CALC_MODE))+"\","+
"\n"+indent3+"\"OrderMode\":\""+IntegerToString(SymbolInfoInteger(symbol, SYMBOL_ORDER_MODE))+"\","+
"\n"+indent3+"\"CalculationMode\":\""+IntegerToString(SymbolInfoInteger(symbol, SYMBOL_TRADE_CALC_MODE))+"\","+
"\n"+indent3+"\"ExecutionMode\":\""+IntegerToString(SymbolInfoInteger(symbol, SYMBOL_TRADE_EXEMODE))+"\","+
"\n"+indent3+"\"ExpirationMode\":\""+IntegerToString(SymbolInfoInteger(symbol, SYMBOL_EXPIRATION_MODE))+"\","+
"\n"+indent3+"\"FillFlags\":\""+IntegerToString(SymbolInfoInteger(symbol, SYMBOL_FILLING_MODE))+"\","+
"\n"+indent3+"\"ExpirFlags\":\""+IntegerToString(SymbolInfoInteger(symbol, SYMBOL_EXPIRATION_MODE))+"\","+
"\n"+indent3+"\"Spread\":\""+IntegerToString(SymbolInfoInteger(symbol, SYMBOL_SPREAD))+"\","+
"\n"+indent3+"\"TickValue\":\""+StringFormat("%G", (SymbolInfoDouble(symbol, SYMBOL_TRADE_TICK_VALUE)))+"\","+
"\n"+indent3+"\"TickSize\":\""+StringFormat("%G", (SymbolInfoDouble(symbol, SYMBOL_TRADE_TICK_SIZE)))+"\","+
"\n"+indent3+"\"ContractSize\":\""+StringFormat("%G",(SymbolInfoDouble(symbol, SYMBOL_TRADE_CONTRACT_SIZE)))+"\","+
"\n"+indent3+"\"StopsLevel\":\""+IntegerToString(SymbolInfoInteger(symbol, SYMBOL_TRADE_STOPS_LEVEL))+"\","+
"\n"+indent3+"\"VolumeMin\":\""+StringFormat("%G",(SymbolInfoDouble(symbol, SYMBOL_VOLUME_MIN)))+"\","+
"\n"+indent3+"\"VolumeMax\":\""+StringFormat("%G",(SymbolInfoDouble(symbol, SYMBOL_VOLUME_MAX)))+"\","+
"\n"+indent3+"\"VolumeStep\":\""+StringFormat("%G",(SymbolInfoDouble(symbol, SYMBOL_VOLUME_STEP)))+"\","+
"\n"+indent3+"\"VolumeLimit\":\""+StringFormat("%G",(SymbolInfoDouble(symbol, SYMBOL_VOLUME_STEP)))+"\","+
"\n"+indent3+"\"SwapMode\":\""+IntegerToString(SymbolInfoInteger(symbol, SYMBOL_SWAP_MODE))+"\","+
"\n"+indent3+"\"SwapLong\":\""+StringFormat("%G",(SymbolInfoDouble(symbol, SYMBOL_SWAP_LONG)))+"\","+
"\n"+indent3+"\"SwapShort\":\""+StringFormat("%G",(SymbolInfoDouble(symbol, SYMBOL_SWAP_SHORT)))+"\","+
"\n"+indent3+"\"Swap3Day\":\""+IntegerToString(SymbolInfoInteger(symbol, SYMBOL_SWAP_ROLLOVER3DAYS))+"\""+
"\n"+indent2+"}"+
"\n"+indent1+"]"+
"\n}";
return(json);
}
//+------------------------------------------------------------------+
//| Form an indent made of spaces |
//+------------------------------------------------------------------+
string Indent(const int number, const int characters=3)
{
int length=number*characters;
string indent=NULL;
StringInit(indent, length, ' ');
return indent;
}
/*
Result:
Database: symbols.sqlite opened successfully
#| cid name type notnull dflt_value pk
-+-------------------------------------------
1| 0 NAME TEXT 1 0
2| 1 DESCRIPTION TEXT 0 0
3| 2 PATH TEXT 0 0
4| 3 SPREAD INT 0 0
5| 4 POINT REAL 1 0
6| 5 DIGITS INT 1 0
7| 6 JSON BLOB 0 0
1: added EURUSD
2: added GBPUSD
3: added USDCHF
...
82: added USDCOP
83: added USDARS
84: added USDCLP
Table SYMBOLS: added 84 symbols
Database: table SYMBOLS saved in symbols.csv
Database: symbols.sqlite created and closed
*/
See also
DatabasePrepare, DatabaseBind, DatabaseBindArray, DatabaseFinalize