Moritz Eyssen

TPC-H 20 fails with s=0.015

SUBSTR refuses DataType::Long arguments, only takes DataType::Int

`LQPColumnReference` consists of a pointer to a node and a ColumnID. This has several disadvantages: * we cannot prune columns in the StoredTableNode, because that would break the ColumnID *...

As @Bouncner pointed out, "SelectExpression" is a potentially confusing name and "SubqueryExpression" is more explicit

`ExpressionEvaluator::evaluate_expression_to_pos_list` could take an optional PosList to restrict checks to. This could improve performance for Expressions involving OR and AND https://github.com/hyrise/hyrise/pull/1170#discussion_r226588508