How to write multi column in clause with sqlalchemy

Question

Please suggest is there way to write query multi-column in clause using SQLAlchemy?

Here is example of the actual query:

SELECT  url FROM pages WHERE         


        

Answer 1

Assuming that you have your model defined in Page, here's an example using tuple_:

keys = [
    (2752937066, 'http://members.aye.net/~gharris/blog/'),
    (3799762538, 'http://www.coxandforkum.com/')
]

select([
    Page.url
]).select_from(
    Page
).where(
    tuple_(Page.url_crc, Page.url).in_(keys)
)

Or, using the query API:

session.query(Page.url).filter(tuple_(Page.url_crc, Page.url).in_(keys))

Answer 2

I do not think this is currently possible in sqlalchemy, and not all RDMBS support this.
You can always transform this to a OR(AND...) condition though:

filter_rows = [
    (2752937066, 'http://members.aye.net/~gharris/blog/'),
    (3799762538, 'http://www.coxandforkum.com/'),
    ]
qry = session.query(Page)
qry = qry.filter(or_(*(and_(Page.url_crc == crc, Page.url == url) for crc, url in filter_rows)))
print qry

should produce something like (for SQLite):

SELECT  pages.id AS pages_id, pages.url_crc AS pages_url_crc, pages.url AS pages_url
FROM    pages
WHERE   pages.url_crc = ? AND pages.url = ? OR pages.url_crc = ? AND pages.url = ?
-- (2752937066L, 'http://members.aye.net/~gharris/blog/', 3799762538L, 'http://www.coxandforkum.com/')

Alternatively, you can combine two columns into just one:

filter_rows = [
    (2752937066, 'http://members.aye.net/~gharris/blog/'),
    (3799762538, 'http://www.coxandforkum.com/'),
    ]
qry = session.query(Page)
qry = qry.filter((func.cast(Page.url_crc, String) + '|' + Page.url).in_(["{}|{}".format(*_frow) for _frow in filter_rows]))
print qry

which produces the below (for SQLite), so you can use IN:

SELECT  pages.id AS pages_id, pages.url_crc AS pages_url_crc, pages.url AS pages_url
FROM    pages
WHERE   (CAST(pages.url_crc AS VARCHAR) || ? || pages.url) IN (?, ?)
-- ('|', '2752937066|http://members.aye.net/~gharris/blog/', '3799762538|http://www.coxandforkum.com/')

Answer 3

I ended up using the test() based solution: generated "(a,b) in ((:a1, :b1), (:a2,:b2), ...)" with named bind vars and generating dictionary with bind vars' values.

params = {}
for counter, r in enumerate(records):
    a_param = "a%s" % counter
    params[a_param] = r['a']
    b_param = "b%s" % counter
    params[b_param] = r['b']
    pair_text = "(:%s,:%s)" % (a_param, b_param)
    enum_pairs.append(pair_text)
multicol_in_enumeration = ','.join(enum_pairs)
multicol_in_clause = text(
    " (a,b) in (" + multicol_in_enumeration + ")")
q = session.query(Table.id, Table.a,
                            Table.b).filter(multicol_in_clause).params(params)

Another option I thought about using mysql upserts but this would make whole included even less portable for the other db engine then using multicolumn in clause.

Update SQLAlchemy has sqlalchemy.sql.expression.tuple_(*clauses, **kw) construct that can be used for the same purpose. (I haven't tried it yet)