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From "Anghel Botos (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (IGNITE-4163) Wrong SQL generated by org.apache.ignite.cache.store.jdbc.dialect.BasicJdbcDialect#loadCacheSelectRangeQuery
Date Fri, 04 Nov 2016 07:07:58 GMT

    [ https://issues.apache.org/jira/browse/IGNITE-4163?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15635499#comment-15635499
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Anghel Botos edited comment on IGNITE-4163 at 11/4/16 7:07 AM:
---------------------------------------------------------------

Additional to my above comment, since having a select that is so nested didn't look quite
nice to me, I also looked at Oracle's {{ROW_NUMBER()}} function. I can get the same results
using a query like this:
{{SELECT KC1, KC2 FROM (SELECT KC1, KC2, ROW_NUMBER() OVER (ORDER BY KC1, KC2) RN FROM MY_TABLE)
WHERE mod(RN, 2)=0;}} (I used {{parallelLoadCacheMinThreshold=2}} just as an example).

Regarding which of the two approaches is better (i.e. more performant) I cannot really say,
as I'm not an Oracle expert, but I found some articles dealing with the topic (e.g. https://explainextended.com/2009/05/06/oracle-row_number-vs-rownum/).
In case you have an Oracle expert amongst your contributors, it might be a good idea to check
with him.


was (Author: abotos):
Additional to my above comment, since having a select that is so nested didn't look quite
nice to me, I also looked at Oracle's {{ROW_NUMBER()}} function. I can get the same results
using a query like this:
{{SELECT KC1, KC2 FROM (SELECT KC1, KC2, ROW_NUMBER() OVER (ORDER BY KC1, KC2) RN FROM MY_TABLE)
WHERE mod(RN, 2)=0;}} (I used {{parallelLoadCacheMinThreshold=2}} just as an example).

Regarding which of the two approaches is better (i.e. more performant) I cannot really say,
as I'm not an Oracle expert, but I found some articles dealing with the topic (e.g. https://explainextended.com/2009/05/06/oracle-row_number-vs-rownum/).
In case you have an Oracle expert in amongst your contributors, it might be a good idea to
check with him.

> Wrong SQL generated by org.apache.ignite.cache.store.jdbc.dialect.BasicJdbcDialect#loadCacheSelectRangeQuery
> ------------------------------------------------------------------------------------------------------------
>
>                 Key: IGNITE-4163
>                 URL: https://issues.apache.org/jira/browse/IGNITE-4163
>             Project: Ignite
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 1.7
>            Reporter: Anghel Botos
>            Assignee: Alexey Kuznetsov
>         Attachments: IGNITE_4163_Oracle_specific_for_load_range_query_.patch
>
>
> The SQL statement generated by org.apache.ignite.cache.store.jdbc.dialect.BasicJdbcDialect#loadCacheSelectRangeQuery
looks like this:
> {{SELECT KEY_COLUMN_1,KEY_COLUMN_2 FROM (SELECT KEY_COLUMN_1,KEY_COLUMN_2, ROWNUM() AS
rn FROM SOME_TABLE ORDER BY KEY_COLUMN_1,KEY_COLUMN_2) WHERE mod(rn, ?) = 0}}
> For Oracle this is incorrect, as Oracle does not have a {{ROWNUM()}} function. For the
above query the following error is thrown: {{ORA-00923: FROM keyword not found where expected}}
> Regarding row numbering Oracle has:
> * a {{ROWNUM}} pseudocolumn, in which case the query should have {{ROWNUM AS rn}}
> * a {{ROW_NUMBER()}} function, in which case the query would become more complicated.
See https://docs.oracle.com/database/121/SQLRF/functions170.htm#SQLRF06100 for more details
about {{ROW_NUMBER()}}
> Please make the neccessary adjustments to either {{BasicJdbcDialect}} or {{OracleDialect}}
so that a correct query is produced.



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