Shuo Cheng created FLINK-20670:
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Summary: Support query hints for Flink SQL
Key: FLINK-20670
URL:
https://issues.apache.org/jira/browse/FLINK-20670 Project: Flink
Issue Type: New Feature
Components: Table SQL / API
Reporter: Shuo Cheng
Fix For: 1.13.0
Now Flink has supported dynamic table options based on the Hint framework of Calcite.
Besides this, Hint syntax is also very useful for query optimization, as there is no perfect planner, and query hints provide a mechanism to direct the optimizer to choose an efficient query execution plan based on the specific criteria.
Currently, almost most popular databases and big-data frameworks support query hint, for example, Join hints in Oracle are used as following:
{code:sql}
SELECT /*+ USE_MERGE(employees departments) */ *
FROM employees, departments
WHERE employees.department_id = departments.department_id;
{code}
Flink also have several join strategy for batch job, i.e., Nested-Loop, Sort-Merge and Hash Join, it will be convenient for users to produce an efficient join execution plan if Flink supports Join hint. Besides Join in batch job, it's also possible to use join hints to support partitioned
temporal table join in future. In a word, query hint, especially join hint now, will benefit Flink users a lot.
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