Additional aliases in qualify_columns rule

[sfc-gh-sgolebiewski]

Hi! Quick question: why qualify_columns rule always force-add aliases on all columns? From docstring:

    Rewrite sqlglot AST to have fully qualified columns.

    Example:
        >>> import sqlglot
        >>> schema = {"tbl": {"col": "INT"}}
        >>> expression = sqlglot.parse_one("SELECT col FROM tbl")
        >>> qualify_columns(expression, schema).sql()
        'SELECT tbl.col AS col FROM tbl'

I would expect default behavior to yield SELECT tbl.col FROM tbl here. This additional alias seems unnecessary to me, am I missing something? 🤔

[georgesittas]

I don't have the full context, but my guess is that it's done to produce a canonicalized AST for later passes.

cc @barakalon @tobymao

[barakalon]

That's right