How to avoid a database hit when instantiating a RWDBStoredProc

Problem

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I want to avoid any unnecessary database hits so I create a RWDBStoredProc with a RWDBSchema. When I try to use this RWDBStoredProc I get an error message from the server like the one below or similar.
[VENDORLIB] Vendor Library Error: Unknown fixed-length datatype encountered.

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Cause

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The RWDBSchema supplied to the constructor of the RWDBStoredProc must contain a RWDBColumn for each parameter and the nativeType and storageLength of the parameter must be specified.

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Action

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Always supply the nativeType and storageLength parameters to the RWDBSchema::appendColumn() method when constucting a schema to pass as an argument to RWDBDatabase::storedProc.The following code demonstrates this for two different stored procedures with Sybase.

#include  #ifdef RW_WRAP_C extern "C" { #endif #include  #include  #ifdef RW_WRAP_C } #endif #include  #include  #include   void myError(const RWDBStatus& st) {   cout << st.message() << endl;   cout << st.vendorError1() << endl;   cout << st.vendorMessage1() << endl;   cout << st.vendorError2() << endl;   cout << st.vendorMessage2() << endl; }   void main() {   RWDBManager::setErrorHandler(myError);  // FILL IN PARAMETERS!!   RWDBDatabase db = RWDBManager::database();

  if (db.isValid() )
    cout << "db is valid" << endl;
  else
    return;

  RWDBTracer& tr = db.tracer();
  tr.setOn(RWDBTracer::SQL);
  tr.stream(cout);
  RWDBConnection conn = db.connection();
  if(conn.isValid())
    cout << "connection is OK" << endl;
  else
    return;

  RWDBSchema schema;

// Either form of appendColumn will work fine, it isn't necessary to specify the column type
// schema.appendColumn("@NAME", RWDBValue::String, 32,47,0,0,FALSE,RWDBColumn::inParameter );
  schema.appendColumn("@NAME", RWDBValue::String, 32,SYBCHAR,0,0);

// schema.appendColumn("@EXT", RWDBValue::Long, 4, 56, 0, 0, FALSE,RWDBColumn::outParameter );
  schema.appendColumn("@EXT", RWDBValue::Long, 4, SYBINT4, 0, 0);

  RWDBStoredProc proc = db.storedProc("GET_EXT", conn, schema);
  RWCString str("janet");
  int ext;
  proc["@NAME"] << str;
  proc["@EXT"] << &ext;
  proc.execute(conn);
  proc.fetchReturnParams();
  cout << "ext is:"  << ext << endl;
  RWDBSchema schemaA;
  schemaA.appendColumn("@MYINT", RWDBValue::Long, 4, 56, 0, 0);
  RWDBStoredProc rspA = db.storedProc("TEST_SELECT_INT", conn, schemaA);
  int iA = -1;
  rspA << &iA;
  rspA.execute(conn);
  rspA.fetchReturnParams();
  cout << "int is:" << iA << endl;

/* 
   this section shows an example of what I can do to
   determine the values for the columns needed above. As
   long as the stored procedure exists in the database 
   this approach will work.  However, I would not include
   this code in my release code as it requires a database
   hit and that's what we want to avoid in our release code. */

  RWDBStoredProc info = db.storedProc("GET_EXT");
  RWDBSchema infoschema = info.params();

  for (size_t i = 0; i < infoschema.entries(); ++i) {
    RWDBColumn col = infoschema.column(i);
    cout << "name:"  << col.name() << endl
	<< "storageLength:"  << col.storageLength() << endl
	<< "nativeType:"  << col.nativeType() << endl
	<< "precision:"  << col.precision() << endl
	<< "scale:" << col.scale() << endl
	<< "nullAllowed:"  << (col.nullAllowed() ? "TRUE" : "FALSE") << endl
	<< "RWDBColumn::ParamType:";
    switch(col.paramType()) {
    case RWDBColumn::notAParameter:
      cout << "RWDBColumn::notAParameter";
    case RWDBColumn::inParameter:
      cout << "RWDBColumn::inParameter";
    case RWDBColumn::outParameter:
      cout << "RWDBColumn::outParameter";
    case RWDBColumn::inOutParameter:
      cout << "RWDBColumn::inOutParameter";
    default:
      cout << "unable to determine parameter type";
    }
    cout << endl;
  }
}