d0ad381833
* test: add spark query unit test and check grammar * test: add select explain、lateralSubQuery、transform unit test * chore: fileName exchange --------- Co-authored-by: dilu <dilu@dtstack.com>
28 lines
1.1 KiB
SQL
28 lines
1.1 KiB
SQL
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-- CLUSTER BY { expression [ , ... ] }
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CREATE TABLE person (name STRING, age INT);
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INSERT INTO person VALUES
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('Zen Hui', 25),
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('Anil B', 18),
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('Shone S', 16),
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('Mike A', 25),
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('John A', 18),
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('Jack N', 16);
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-- Reduce the number of shuffle partitions to 2 to illustrate the behavior of `CLUSTER BY`.
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-- It's easier to see the clustering and sorting behavior with less number of partitions.
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SET spark.sql.shuffle.partitions = 2;
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-- Select the rows with no ordering. Please note that without any sort directive, the results
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-- of the query is not deterministic. It's included here to show the difference in behavior
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-- of a query when `CLUSTER BY` is not used vs when it's used. The query below produces rows
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-- where age column is not sorted.
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SELECT name, age FROM person;
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-- Produces rows clustered by age. Persons with same age are clustered together.
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-- In the query below, persons with age 18 and 25 are in first partition and the
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-- persons with age 16 are in the second partition. The rows are sorted based
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-- on age within each partition.
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SELECT age, name FROM person CLUSTER BY age;
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