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From "Bryan Pendleton (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-3603) 'IN' clause ignores valid results, incorrect qualifier handling suspected
Date Wed, 09 Apr 2008 01:49:25 GMT

    [ https://issues.apache.org/jira/browse/DERBY-3603?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12587030#action_12587030
] 

Bryan Pendleton commented on DERBY-3603:
----------------------------------------

Just for completeness, I repeated Kathey's experiment on the trunk;
I backed out the DERBY-3061 change and the query then returns 3 rows.
So that's more evidence that DERBY-3061's change is relevant, but I'm
afraid I don't have any theories to contribute about why that is.

I do notice that in DERBY-3061, the query in question has two conditions
on the same column, where one is clearly "stronger" than the other:

   where mytable.id < 100
   and mytable.id in ( 2, 15, 19, 20, 21, 48, 49 );

However, in this issue, the query in question has two conditions on the
same column, where both conditions should (apparently) be of the same
"strength", since both are (according to the DERBY-3061 changes) to be
treated as equality:

   WHERE   admin_unit.admin_unit_id IN (1,21) AND
      admin_unit.admin_unit_id = account.admin_unit_id; 

This similarity in query structure appears to explain why the DERBY-3061
changes are relevant.



> 'IN' clause ignores valid results, incorrect qualifier handling suspected
> -------------------------------------------------------------------------
>
>                 Key: DERBY-3603
>                 URL: https://issues.apache.org/jira/browse/DERBY-3603
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.3.2.1, 10.4.1.1
>            Reporter: David Butterworth
>         Attachments: derbydb.tar.bz2
>
>
> Derbys' 'IN' clause is returning different results depending on which side of a joined
table
> I am doing my 'IN' comparison against. This only occurs when the number of items within
the 'IN' clause is greater then 1.
> This behaviour was also confirmed by Bryan Pendleton in this thread:
> http://mail-archives.apache.org/mod_mbox/db-derby-user/200804.mbox/%3c47FA5974.2060705@amberpoint.com%3e
> Using the test database attatched the following 2 queries produce the issue:
> ij>  select count(*) FROM spike.accounts account, spike.admin_units admin_unit,
>     spike.bookings booking
>     WHERE booking.child_id = 2 AND
>     admin_unit.admin_unit_id IN (1,21) AND
>     booking.booking_date_time_out >= 20080331000000 AND
>     booking.booking_date_time_in <= 20080406235900 AND
>     account.account_id = booking.account_id AND
>     admin_unit.admin_unit_id = account.admin_unit_id;
> 1          
> -----------
> 2          
> 1 row selected
> ij> select count(*) FROM spike.accounts account, spike.admin_units admin_unit,
>     spike.bookings booking
>     WHERE booking.child_id = 2 AND
>     account.admin_unit_id IN (1,21) AND
>     booking.booking_date_time_out >= 20080331000000 AND
>     booking.booking_date_time_in <= 20080406235900 AND
>     account.account_id = booking.account_id AND
>     admin_unit.admin_unit_id = account.admin_unit_id;
> 1          
> -----------
> 3          
> 1 row selected
> ij> 
> The only difference between the 2 statements is which side of a join the 'IN' clause
is matched against.
> Bryan performed some initial testing and stated the following:
> --------------------- SNIP ------------------------
> Interestingly, although the actual results do NOT contain any values
> for admin_unit_id = 21, if I change the query to:
>     admin_unit.admin_unit_id IN (1)
> or
>     account.admin_unit_id IN (1)
> then the problem disappears -- I get 3 rows for both queries.
> I also ran query plans for both the queries (in the IN (1,21) case)
> and have pasted the (simplified) query plans at the end of this message.
> I notice that in the case where the query gives 2 rows, which is
> when we specify admin_unit.admin_unit_id in (1,21), the admin_unit_id
> index scan output in the query plan contains:
>            qualifiers:
> Column[0][0] Id: 0
> Operator: =
> Ordered nulls: false
> Unknown return value: false
> Negate comparison result: false
> However, in the case where the query gives 3 rows, which is
> when we specify account.admin_unit_id in (1,21), the admin_unit_id
> index scan output in the query plan contains:
>            qualifiers:
> None
> I think it is the presence/absence of this qualifier on the query
> scan which is causing the different results in the query, as in
> the first case we see:
>            Number of rows qualified=2
>            Number of rows visited=3
> but in the second case we see:
>            Number of rows qualified=3
>            Number of rows visited=3
> I definitely don't have any explanation for why you are getting
> this odd behavior; it certainly seems like a bug to me.
> -------------END SNIP -----------------------

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