[SPARK-30589][DOC] Document DISTRIBUTE BY Clause of SELECT statement in SQL Reference #27298
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Test build #117140 has finished for PR 27298 at commit
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huaxingao
reviewed
Jan 21, 2020
| limitations under the License. | ||
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| The <code>DISTRIBUTE BY</code> clause is used to repartition the data based | ||
| on the input expressions. Unlike the `CLUSTER BY` clause, this does not |
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@huaxingao will do it in the finalization pr when the links are available.
huaxingao
reviewed
Jan 21, 2020
| ('John A', 18), | ||
| ('Jack N', 16); | ||
| -- Reduce the number of shuffle partitions to 2 to illustrate the behaviour of `DISTRIBUTE BY`. | ||
| -- Its easier to see the clustering and sorting behaviour with less number of partitions. |
huaxingao
reviewed
Jan 21, 2020
| 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 | ||
| -- of the query is not deterministic. Its included here to just contrast it with the |
huaxingao
reviewed
Jan 21, 2020
| -- Its easier to see the clustering and sorting behaviour with less number of partitions. | ||
| 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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the results of the query is... -> the result of the query is...?
huaxingao
reviewed
Jan 21, 2020
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| -- Select the rows with no ordering. Please note that without any sort directive, the results | ||
| -- of the query is not deterministic. Its included here to just contrast it with the | ||
| -- behaviour of `DISTRIBUTE BY`. The query below produces rows where age column are not |
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age column are not... -> age columns are not...?
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Test build #117148 has finished for PR 27298 at commit
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huaxingao
reviewed
Jan 23, 2020
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| ### Syntax | ||
| {% highlight sql %} | ||
| DISTRIBUTE BY { expression [ , ...] } |
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Test build #117278 has finished for PR 27298 at commit
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Test build #117300 has finished for PR 27298 at commit
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Merged to master. @dilipbiswal did you want to make a follow up to link several pages? |
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@srowen Thanks a lot Sean. Yeah.. I will do it today. |
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What changes were proposed in this pull request?
Document DISTRIBUTE BY clause of SELECT statement in SQL Reference Guide.
Why are the changes needed?
Currently Spark lacks documentation on the supported SQL constructs causing
confusion among users who sometimes have to look at the code to understand the
usage. This is aimed at addressing this issue.
Does this PR introduce any user-facing change?
Yes.
Before:
There was no documentation for this.
After.
How was this patch tested?
Tested using jykyll build --serve