Jesus Camacho Rodriguez created HIVE-20090:
----------------------------------------------
Summary: Extend creation of semijoin reduction filters to be able
to discover new opportunities
Key: HIVE-20090
URL: https://issues.apache.org/jira/browse/HIVE-20090
Project: Hive
Issue Type: Improvement
Components: Physical Optimizer
Reporter: Jesus Camacho Rodriguez
Assignee: Jesus Camacho Rodriguez
Assume the following plan:
{noformat}
TS[0] - RS[1] - JOIN[4] - RS[5] - JOIN[8] - FS[9]
TS[2] - RS[3] - JOIN[4]
TS[6] - RS[7] - JOIN[8]
{noformat}
Currently, {{TS\[6\]}} may only be reduced with the output of {{RS\[5\]}},
i.e., input to join between both subplans.
However, it may be useful to consider other possibilities too, e.g., reduced by
the output of {{RS\[1\]}} or {{RS\[3\]}}. For instance, this is important when,
given a large plan, an edge between {{RS[5]}} and {{TS[0]}} would create a
cycle, while an edge between {{RS[1]}} and {{TS[6]}} would not.
This patch comprises two parts. First, it creates additional predicates when
possible. Secondly, it removes duplicate semijoin reduction
branches/predicates, e.g., if another semijoin that consumes the output of the
same expression already reduces a certain table scan operator (heuristic, since
this may not result in most efficient plan in all cases). Ultimately, the
decision on whether to use one or another should be cost-driven (follow-up).
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
