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Alex Rodoni closed IMPALA-8945. ------------------------------- Fix Version/s: Impala 3.4.0 Resolution: Fixed > Impala Doc: Incorrect Claim of Equivalence in Impala Docs > --------------------------------------------------------- > > Key: IMPALA-8945 > URL: https://issues.apache.org/jira/browse/IMPALA-8945 > Project: IMPALA > Issue Type: Bug > Components: Docs > Reporter: Alex Rodoni > Assignee: Alex Rodoni > Priority: Major > Fix For: Impala 3.4.0 > > > Reported by [~icook] > The Impala docs entry for the IS DISTINCT FROM operator states: > The <=> operator, used like an equality operator in a join query, is more > efficient than the equivalent clause: A = B OR (A IS NULL AND B IS NULL). The > <=> operator can use a hash join, while the OR expression cannot. > But this expression is not equivalent to A <=> B. See the attached screenshot > demonstrating their non-equivalence. An expression that is equivalent to A > <=> B is this: > (A IS NULL AND B IS NULL) OR ((A IS NOT NULL AND B IS NOT NULL) AND (A = B)) > This expression should replace the existing incorrect expression. > Another expression that is equivalent to A <=> B is: > if(A IS NULL OR B IS NULL, A IS NULL AND B IS NULL, A = B) > This one is a bit easier to follow. If you use this one in the docs, just > replace the following line with: > The <=> operator can use a hash join, while the if expression cannot. -- This message was sent by Atlassian Jira (v8.3.2#803003)