this sounds like the select() object was being used incorrectly, using a pattern that currently emits very prominent deprecation warnings which is: stmt = s

this sounds like the select() object was being used incorrectly, using a pattern that currently emits very prominent deprecation warnings which is: stmt = select(...) stmt = stmt.where(stmt.c.foo == 'bar') stmt = stmt.where(stmt.c.bar == 'xyz') That above pattern is one I've seen people do even recently, using the "select().c" attribute which from very early versions of SQLAlchemy is defined as "the columns from a subquery of the SELECT" ; this usage began raising deprecation warnings in 1.4 and should be fully removed by 2.1 as it was a remnant of a much earlier version of SQLAlchemy. it will do exactly as you say, "make a subquery for each filter condition" and will produce disastrous queries. people have started tripping over it recently as a result of 1.4 / 2.0's move away from the ORM `Query` object back towards `select()`. the moment you see SQLAlchemy doing something you see that seems "asinine", send an example to https://github.com/sqlalchemy/sqlalchemy/discussions https://github.com/sqlalchemy/sqlalchemy/discussions and I will clarify what's going on, correct the usage so that the query you have is what you expect, and quite often we will add new warnings or documentation when we see people doing things we didn't anticipate (such as in this case, I thought we had removed .c by 2.0 but apparently it's still just deprecated. it will be gone in 2.1).