[#CORE-1943] GROUP BY RAND() returns infinite rows

Firebird Core

GROUP BY RAND() returns infinite rows

Created: 19/Jun/08 01:08 PM Updated: 25/Apr/11 02:08 PM

Component/s:

Engine

Affects Version/s:

2.1.0, 2.0.4

Fix Version/s:

2.5 Beta 1

Time Tracking:

Not Specified

Issue Links:

Relate

This issue is related to:

~~QA-349~~ Test for CORE-1943

Planning Status:

Unspecified

Description

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The query below returns infinite rows:

select
1
from
rdb$database a
group by
rand()

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Sean Leyne added a comment - 19/Jun/08 01:13 PM

Fabiano,

This seems to be a "non-sense case" -- it does not reflected anything close to a real-world scenario -- as such, I think this should be considered a "won't fix" case.

Can you explain why GROUP BY RAND() would ever be used?

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Adriano dos Santos Fernandes added a comment - 19/Jun/08 02:02 PM

Database engines should deal with "non-sense cases" too. Job of GROUP BY is not produce rows.

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Dmitry Yemanov added a comment - 19/Jun/08 02:34 PM

I agree with Adriano. We already had such a problem previously with GROUP BY <constant>. The current one should also be solved. Our GROUP BY processing is somewhat non-optimal (to say at least).

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fabianobonin added a comment - 19/Jun/08 06:28 PM

In my case, i was grouping by a "case", 'cause i need to group some rows from a procedure and keep others not grouped, but as the procedure didn't have a unique column, i used rand() to fake one. I fixed it changing the procedure to return a unique column and using it instead.

group by
case when ... then ... else rand() end

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Pavel Cisar added a comment - 25/Apr/11 02:08 PM

QA test added.