On Fri, May 12, 2017 at 7:09 AM, Alexander Kuzmenkov <a.kuzmen...@postgrespro.ru> wrote: > As you know, at this time Postgres cannot perform a full join on a > comparison clause. For example, if we have two tables with numeric columns > and run a query like 'select * from t1 full join t2 on t1.a > t2.a', we get > an error: "FULL JOIN is only supported with merge-joinable or hash-joinable > join conditions". Such queries are legitimate SQL and sometimes arise when > porting applications from different DBMS, so it would be good to support > them in Postgres. They can be rewritten as union of right and left joins, > but it requires manual work and runs somewhat slower (see the benchmark at > the end of the letter). This proof-of-concept patch explores the possibility > of performing such queries as merge joins.
Interesting. I suggest adding this to the next CommitFest. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
