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https://issues.apache.org/jira/browse/LENS-714?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Arshad Matin closed LENS-714.
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> Replace dimension tables with subquery in Columnar Rewriter
> -----------------------------------------------------------
>
> Key: LENS-714
> URL: https://issues.apache.org/jira/browse/LENS-714
> Project: Apache Lens
> Issue Type: Improvement
> Components: driver-jdbc
> Reporter: Sushil Mohanty
> Assignee: Sushil Mohanty
> Fix For: 2.3
>
> Attachments: LENS-714-2.patch
>
>
> In order to optimise the JDBC sql queries, we can skip directly joining with
> the dimension tables. Instead we can create a subquery with only required
> column for a table used in the query. For eg. If column id and name are
> queried from table dim1 the query can be rewritten as
> ... inner join (select id,name from dim1) as d1 instead of ...inner join dim1
> as d1.
> For dimension tables with descent size this helps in improving performance to
> a great extent. Planning to add this in ColumnarRewriter so that columnar DBs
> can leverage this.
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