How do you remove a node from the tree?

[g-u-t-h-m-a-n]

I'm trying to achieve something to this effect:

def transformer(node):
    if isinstance(node, sqlglot.exp.Predicate) and 'some_text' in node.text('this'):
        node.delete()
    return node

expression_tree.transform(transformer)

But I can't figure out what method is available for this, or how to do this otherwise.

[tobymao]

It's a bit tricky to just delete a node, you could do return exp.TRUE to replace the node with a TRUE constant. you could then use the optimizer's simplify functionality to remove unnecessary TRUE statements

another way is that you can replace the parent with a new expression with this part removed

so

def transform(node):
   if ...is_parent...:
       return condition_with_predicate_removed

[georgesittas]

@g-u-t-h-m-a-n you can now also do the following (relevant commit):

from sqlglot import exp, parse_one

expression_tree = parse_one("SELECT a, b FROM x")

def fun(node):
    if isinstance(node, exp.Column) and node.name == "b":
        return None
    return node

transformed_tree = expression_tree.transform(fun)
transformed_tree.sql()

Which outputs:

SELECT a FROM x

Also, you can remove specific nodes by calling their pop method.