[zzzeek]

OK, here's something I should understand. Say we start with:

    myquery = select(c for c in Customer if sum(c.orders.total_price) > 1000)

I'm inside of a query builder. Based on conditional logic, I also want to alter the above statement to include customer.name > 'G'. Intuitively, I'd do this:

    mynewquery = select(c for c in myquery if c.name > 'G')

which will take the original SELECT, wrap it in a whole new SELECT. Right?

Given "myquery", how do I add, after the fact, a simple "WHERE customer.name > 'G"" to the SELECT? Just continuously wrapping in subqueries is obviously not feasible.

[amalashkevich]

There is no need to wrap it with a query. You can just add a filter:

    mynewquery = myquery.filter(lambda c: c.name > 'G')

The new query will produce the following SQL:

    SELECT `c`.`id`
    FROM `customer` `c`
      LEFT JOIN `order` `order-1`
        ON `c`.`id` = `order-1`.`customer`
    WHERE `c`.`name` > 'G'
    GROUP BY `c`.`id`
    HAVING coalesce(SUM(`order-1`.`total_price`), 0) > 1000

[zzzeek]

Well right, this is exactly a SQLAlchemy-style syntax, except a tad more verbose :). This is the "dropping into a SQLAlchemy-style approach" I referred to.

As far as the "AST allows caching" advantage, over at https://bitbucket.org/zzzeek/sqlalchemy/issue/3054/new-idea-... we're working out a way to give people access to the "lambda: <X>" -> cached SQL in a similar way, if they want it.