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https://issues.apache.org/jira/browse/DRILL-4618?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15563103#comment-15563103
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ASF GitHub Bot commented on DRILL-4618:
---------------------------------------
Github user sudheeshkatkam commented on the issue:
https://github.com/apache/drill/pull/509
+1
> random numbers generator function broken
> ----------------------------------------
>
> Key: DRILL-4618
> URL: https://issues.apache.org/jira/browse/DRILL-4618
> Project: Apache Drill
> Issue Type: Bug
> Reporter: Chunhui Shi
> Assignee: Boaz Ben-Zvi
>
> File this JIRA based on the the bug description from Ted's email and
> discussion in dev mail list for record purpose:
> I am trying to generate some random numbers. I have a large base file (foo)
> this is what I get:
> 0: jdbc:drill:> select floor(1000*random()) as x, floor(1000*random()) as
> y, floor(1000*rand()) as z from (select * from maprfs.tdunning.foo) a limit
> 20;
> +--------+--------+--------+
> | x | y | z |
> +--------+--------+--------+
> | 556.0 | 556.0 | 618.0 |
> | 564.0 | 564.0 | 618.0 |
> | 129.0 | 129.0 | 618.0 |
> | 48.0 | 48.0 | 618.0 |
> | 696.0 | 696.0 | 618.0 |
> | 642.0 | 642.0 | 618.0 |
> | 535.0 | 535.0 | 618.0 |
> | 440.0 | 440.0 | 618.0 |
> | 894.0 | 894.0 | 618.0 |
> | 24.0 | 24.0 | 618.0 |
> | 508.0 | 508.0 | 618.0 |
> | 28.0 | 28.0 | 618.0 |
> | 816.0 | 816.0 | 618.0 |
> | 717.0 | 717.0 | 618.0 |
> | 334.0 | 334.0 | 618.0 |
> | 978.0 | 978.0 | 618.0 |
> | 646.0 | 646.0 | 618.0 |
> | 787.0 | 787.0 | 618.0 |
> | 260.0 | 260.0 | 618.0 |
> | 711.0 | 711.0 | 618.0 |
> +--------+--------+--------+
> On this page, https://drill.apache.org/docs/math-and-trig/, the rand
> function is described and random() is not. But it appears that rand()
> delivers a constant instead (although a different constant each time the
> query is run) and it appears that random() delivers the same value when
> used multiple times in each returned value.
> This seems very, very wrong.
> The fault does not seem to be related to my querying a table:
> 0: jdbc:drill:> select rand(), random(), random() from (values (1),(2),(3))
> x;
> +---------------------+-----------------------+-----------------------+
> | EXPR$0 | EXPR$1 | EXPR$2 |
> +---------------------+-----------------------+-----------------------+
> | 0.1347749257216052 | 0.36724556209765014 | 0.36724556209765014 |
> | 0.1347749257216052 | 0.006087161689924625 | 0.006087161689924625 |
> | 0.1347749257216052 | 0.09417099142512142 | 0.09417099142512142 |
> +---------------------+-----------------------+-----------------------+
> For reference, postgres doesn't have rand() and does the right thing with
> random().
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