sql - When did sqlalchemy execute the query? -

as i've start learning use sqlalchemy recently, result of following code make me confused when sqlalchemy execute query:

query = db.session.query(mytable) query = query.filter(...)     query = query.limit(...)    query = query.offset(...)     records = query     #records=query.all() r in records:     #do 

note line

records = query #records=query.all() 

seems brings same correct result(stored in variable "records") when using "query" , "query.all()", wonder when query executed?

if executed during first line "db.session.query(mytable)", result set may large @ point; if during fifth line "records = query", how happen there's no function call @ all?

in example, query gets executed upon for r in records. accessing query object via iterator triggers execution. (normally, compiled select statement)

up until time, query built (via filter, limit etc).

please read orm tutorial on querying