[jira] [Created] (DRILL-4618) random numbers generator function broken

["Chunhui Shi (JIRA)" <ji...@apache.org>]

Chunhui Shi created DRILL-4618:
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             Summary: 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


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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