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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:
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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.
was (Author: abotos):
Additional to my above comment, since having a select that is so nested 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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