[jira] [Created] (IGNITE-6085) SQL: JOIN with multiple conditions is extremely slow

["Vladimir Ozerov (JIRA)" <ji...@apache.org>]

Vladimir Ozerov created IGNITE-6085:
---------------------------------------

             Summary: SQL: JOIN with multiple conditions is extremely slow
                 Key: IGNITE-6085
                 URL: https://issues.apache.org/jira/browse/IGNITE-6085
             Project: Ignite
          Issue Type: Task
          Components: sql
    Affects Versions: 2.1
            Reporter: Vladimir Ozerov
             Fix For: 2.2


Consider the following query:
{code}
SELECT ... FROM A a
    INNER JOIN B b ON b.id = a.foreign_id1 OR b.id = a.foreign_id2
{code}

In this case H2 cannot use indexes on {{foreign_id1}} or {{foreign_id2}} columns and query execution takes extraordinary time. Known workaround for a problem is to apply multiple JOINs, e.g.:
{code}
SELECT ... FROM A a
    LEFT OUTER JOIN B b1 ON b1.id = a.foreign_id1 
    LEFT OUTER JOIN B b2 ON b2.id = a.foreign_id2
WHERE b1.id IS NOT NULL AND b2.id IS NOT NULL
{code}
On a single real-world scenario it improved exeution time by a factor of 500 (from 4s to 80ms).

Something is terribly wrong here. Probably, H2 cannot perform necessary query re-write, or cannot understand how to use index. Let's find a way to fix that.



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