Querying a composite key in SQLAlchemy-ORM -

background

i have composite index defined on sqlalchemy object, say:

class shirt(base):     __tablename__ = 'shirt'     id = column(integer, primary_key=true)     size = column(string(32))   # e.g. small, medium large     color = column(string(32))  # e.g. blue, red, white  index('color_size', shirt.size, shirt.color) 

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question

i'd search small , red shirts, taking advantage of color_size composite index.

how write query?

would use of and_() automatically take advantage of index?
example:

results = shirt.query.filter( and_(shirt.size=='small', shirt.color=='red') ).all() 

yes, index should used. sqlalchemy isn't using index though, defines index. it's database use given query.

you can use explain prove index being used. example, postgresql shows index scan.

example => explain select id shirt color = 'red' , size = 'small';                                     query plan                                     ----------------------------------------------------------------------------------  index scan using ix_shirt_size_color on shirt  (cost=0.15..8.17 rows=1 width=4)    index cond: (((size)::text = 'small'::text) , ((color)::text = 'red'::text))