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https://issues.apache.org/jira/browse/DRILL-3180?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14790714#comment-14790714
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Jacques Nadeau commented on DRILL-3180:
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I think you may be depending on a behavior of particular dbs. The opinions of
[~julianhyde], [~jni] and [~amansinha100] would probably be helpful here. If my
query has an *INNER* join with an additional single-table join-local filter
condition, then all of these are logically equivalent:
- filter condition applied as part of join evaluation
- filter applied after join evaluation
- filter applied before join evaluation
As such, In Drill we should be able to rewrite to any of those and things
should be ok. Additionally, a derived table expressed in the same query also
does not force/guarantee the ordering of operations. The optimizers purpose to
is to find all equivalent sets and then pick what it thinks is the best one. If
you can force the optimizer to order operations implicitly, that would mean
less good SQL writers would compose bad SQL and the optimizer couldn't do
anything about it.
That being said, the conversation of logical equivalencies is really separate
from what you really want: push down the join even their if there is an
additional filter condition within the join. That seems reasonable and could be
done on the Calcite project, specifically right here:
https://github.com/apache/incubator-calcite/blob/master/core/src/main/java/org/apache/calcite/adapter/jdbc/JdbcRules.java#L201
Please note, that doesn't mean that you should expect a particular sql
construction to be passed to the underlying jdbc system. This is because the
expression goes through the Calcite optimizer. So while you may compose the
query with a filter as part of the join condition, that Drill may output the
query to the JDBC source using a different but equal pattern. This should be
expected as Drill should produce a logically equivalent dataset.
This all changes if the join with the condition is an OUTER join.
> Apache Drill JDBC storage plugin to query rdbms systems such as MySQL and
> Netezza from Apache Drill
> ---------------------------------------------------------------------------------------------------
>
> Key: DRILL-3180
> URL: https://issues.apache.org/jira/browse/DRILL-3180
> Project: Apache Drill
> Issue Type: New Feature
> Components: Storage - Other
> Affects Versions: 1.0.0
> Reporter: Magnus Pierre
> Assignee: Jacques Nadeau
> Labels: Drill, JDBC, plugin
> Fix For: 1.2.0
>
> Attachments: patch.diff, pom.xml, storage-mpjdbc.zip
>
> Original Estimate: 1m
> Remaining Estimate: 1m
>
> I have developed the base code for a JDBC storage-plugin for Apache Drill.
> The code is primitive but consitutes a good starting point for further
> coding. Today it provides primitive support for SELECT against RDBMS with
> JDBC.
> The goal is to provide complete SELECT support against RDBMS with push down
> capabilities.
> Currently the code is using standard JDBC classes.
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