Jihoon Son created TAJO-1310:
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Summary: Maintaining join filters in join operators
Key: TAJO-1310
URL: https://issues.apache.org/jira/browse/TAJO-1310
Project: Tajo
Issue Type: Improvement
Components: parser, physical operator, planner/optimizer
Reporter: Jihoon Son
Assignee: Jihoon Son
Priority: Blocker
Fix For: 0.11
*Introduction*
A join statement can contain join predicates and join filters.
Join predicates are evaluated during performing the join operation, while join
filters are evaluated on the set of join results.
Let me consider an example join query as follows:
{noformat}
default> select n_nationkey from nation left outer join region on n_nationkey =
r_regionkey where r_regionkey is null;
{noformat}
In this query, the join predicates and filters are as follows:
* Join predicates: n_nationkey = r_regionkey
* Join filters: r_regionkey is null
*Problem*
Currently, in query plans, join filters are handled as selection operators,
while join predicates are maintained as member variables of join operators.
This approach makes the implementation simple, but difficult to find the
selection operators corresponding to join operators because they are separately
maintained.
This problem is critical when the logical plan optimizer optimizes the join
order of a query statement that contains two or more joins each of that has
join filters.
*Solution*
Join filters should be distinguished from selection filters, and maintained in
the corresponding join operators. For this, we should add join filtlers to the
join expression, the logical join node, and several physical join executors.
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