procedure TSqlDBPostgresConnectionProperties.FillOidMapping;
begin
  // see pg_type.h (most used first)
  MapOid(INT4OID,        ftInt64);
  MapOid(INT8OID,        ftInt64);
  MapOid(TEXTOID,        ftUtf8); // other char types will be ftUtf8 as fallback
  MapOid(FLOAT8OID,      ftDouble);
  MapOid(TIMESTAMPOID,   ftDate);
  MapOid(BYTEAOID,       ftBlob);
  MapOid(NUMERICOID,     ftDouble); // our ORM uses NUMERIC(19,4) for currency
  MapOid(BOOLOID,        ftInt64);
  MapOid(INT2OID,        ftInt64);
  MapOid(CASHOID,        ftCurrency);
  MapOid(TIMESTAMPTZOID, ftDate);
  MapOid(ABSTIMEOID,     ftDate);
  MapOid(DATEOID,        ftDate);
  MapOid(TIMEOID,        ftDate);
  MapOid(TIMETZOID,      ftDate);
  MapOid(REGPROCOID,     ftInt64);
  MapOid(OIDOID,         ftInt64);
  MapOid(FLOAT4OID,      ftDouble);
  // note: any other unregistered OID will be handled as ftUtf8 to keep the data
end;

        mormot.db.core.ftUtf8:
          if ColumnDataSize = 0 then
            dbtype := ftDefaultMemo
          else // no size
            dbtype := ftWideString; // means UnicodeString for Delphi 2009+

        mormot.db.core.ftUtf8:
          dbtype := ftString;

procedure TBinaryDataSet.InternalInitFieldDefs;
var
  f, custom: PtrInt;
  dbtype: TFieldType;
  names: TRawUtf8DynArray; // FieldDefs.Items[].Name
  sizes: TIntegerDynArray; // FieldDefs.Items[].Size
begin
  if FieldDefs.Count > 0 then
  begin // custom column sizes
    SetLength(names, FieldDefs.Count);
    SetLength(sizes, FieldDefs.Count);
    for f := 0 to FieldDefs.Count - 1 do
      with FieldDefs.Items[f] do
      begin
        names[f] := StringToUtf8(Name);
        sizes[f] := Size;
      end;
  end;
  FieldDefs.Clear;
  if fDataAccess = nil then
    exit;
  for f := 0 to fDataAccess.ColumnCount - 1 do
    with fDataAccess.Columns[f] do
    begin
      if names <> nil then
      begin
        custom := FindRawUtf8(names, ColumnName);
        if custom >= 0 then // retrieve custom max column length from FieldDefs
          ColumnDataSize := sizes[custom];
      end;
      case ColumnType of
        mormot.db.core.ftInt64:
          dbtype := ftLargeint;
        mormot.db.core.ftDate:
          dbtype := ftDateTime;
        mormot.db.core.ftUtf8:
          dbtype := ftString;
          {
          if ColumnDataSize = 0 then
            dbtype := ftDefaultMemo
          else // no size
            dbtype := ftWideString; // means UnicodeString for Delphi 2009+
            }
        mormot.db.core.ftBlob:
          dbtype := ftBlob;
        mormot.db.core.ftDouble,
        mormot.db.core.ftCurrency:
          dbtype := ftFloat;
      else
        raise EVirtualDataSet.CreateUtf8('%.GetFieldData ColumnType=%',
          [self, TSqlDBFieldTypeToString(ColumnType)]);
      end;
      FieldDefs.Add(Utf8ToString(ColumnName), dbtype, ColumnDataSize);
    end;
end;