Hello!
It looks that SQLAlchemy doesn't properly handle union with limits in
the following scenario:
res1 = Session.query( Messages ).order_by( Messages.ts ).limit(100)
res2 = Session.query( Messages1 ).order_by( Messages1.ts ).limit(100)
res3 = res1.union_all( res2 )
SQLAlchemy creates the following final query:
SELECT <fields> FROM Messages order by ts limit 100
UNION ALL SELECT <fields> FROM Messages1 order by ts limit 100
Which fails with:
ProgrammingError: (psycopg2.ProgrammingError) syntax error at or near
"UNION"
To fix this, both queries should be enclosed in parenthesis:
(SELECT <fields> FROM Messages order by ts limit 100 )
UNION ALL ( SELECT <fields> FROM Messages1 order by ts limit 100 )
Best regards
Jarek
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The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
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