public void Dispose()
{
foreach (var dbreader in TableReaders)
{
dbreader.Dispose();
}
TableReaders.Clear();
}
/// <summary>
/// execute query to get result rows
/// </summary>
/// <returns></returns>
public IEnumerable <object[]> Rows()
{
//only for one table for now
var table = Query.Tables.First();
var handler = TableReaders.FirstOrDefault(r => r.Table.Name == table.Name);
var collection = Enumerable.Empty <int>();
if (!Query.Where.Defined)
{
//no WHERE, ALL table
//return the full table rows
//later mix all tables according to FROM tables and SELECT rows
var type = handler.GetType();
var method = type.GetMethod(nameof(DbTableDataReader.Rows),
BindingFlags.Instance | BindingFlags.NonPublic);
MethodInfo genMethod = method.MakeGenericMethod(handler.Table.Type);
//get first key
var key = handler.Table.Columns.FirstOrDefault(c => c.Key);
collection = (IEnumerable <int>)genMethod.Invoke(handler, new object[] { key });
}
else
{
//filtered table
collection = ExecuteWhere(Query.Where.Root as DbQuery.ExpressionOperator);
}
//TOP
if (Query.Select.Top > 0)
{
collection = collection.Take(Query.Select.Top);
}
//process collection of offsets
if (Query.Select.IsFunction)
{
RowCount = 1;
//query functions contains only one column in SELECT
var column = SelectIndexColumns.Columns.First();
var valueType = column.Type;
if (Query.Select.Function == TokenType.COUNT)
{
//Enumerable.Count() returns an int
yield return(new object[] { collection.Count() });
}
else
{
if (!valueType.IsNumeric())
{
throw new ArgumentException($"function {Query.Select.Function} column type must be numeric");
}
MethodInfo method =
this.GetType().GetMethod(nameof(ExecuteFunction), BindingFlags.Instance | BindingFlags.NonPublic);
MethodInfo genMethod = method.MakeGenericMethod(Type.GetType($"System.{valueType}"));
var result = genMethod.Invoke(this, new object[] { handler, valueType, collection });
yield return(new object[] { result });
}
}
else
{
//output all rows filtered or not
RowCount = 0;
foreach (var offset in collection)
{
RowCount++;
yield return(handler.ReadRecord(offset));
}
}
}
