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https://issues.apache.org/jira/browse/CALCITE-7803?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18118291#comment-18118291
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Stamatis Zampetakis commented on CALCITE-7803:
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Thanks for the feedback Julian! I can add a page to the website listing useful
tools starting with this one. However, the main intention behind this proposal
is to use the Java API directly (via Impala, Hive, and possibly another Java
project). For the use-cases I have in mind a CLI interface is not necessary at
the moment.
> Extract rewritable materialized view fragments from queries
> -----------------------------------------------------------
>
> Key: CALCITE-7803
> URL: https://issues.apache.org/jira/browse/CALCITE-7803
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Reporter: Stamatis Zampetakis
> Assignee: Stamatis Zampetakis
> Priority: Major
>
> The MaterializedViewRules impose limitations on the shape of a query/plan
> that can be used for query rewriting. There is a [validity
> check|https://github.com/apache/calcite/blob/34db6c8cd895998f38175efc3e3306311fc7d061/core/src/main/java/org/apache/calcite/rel/rules/materialize/MaterializedViewRule.java#L503]
> that must be satisfied both by the operator matching the rule and the
> materialized view candidate. In a nutshell only SPJA query/plans are allowed
> with a few additional restrictions.
> The goal of this ticket is to add a new API/utility able to extract
> rewritable materialized view fragments form an input query/plan. A fragment
> is rewritable if it passes the validity check present in the materialized
> view rules. The visitor should only extract maximal fragments; no containment
> relationships among fragments.
> Consider the following query having a union with two branches. Observe that
> both of the branches are rewritable but the whole query is not due to the
> union.
> +Input+
> {code:sql}
> SELECT ename FROM emp WHERE empno = 1
> UNION
> SELECT ename FROM emp WHERE empno = 2
> {code}
> +Fragment 1+
> {code:sql}
> SELECT ename FROM emp WHERE empno = 1
> {code}
> +Fragment 2+
> {code:sql}
> SELECT ename FROM emp WHERE empno = 2
> {code}
> The {{SELECT ename FROM emp}} is also a rewritable fragment but its not
> maximal thus its not part of the result. The examples above appear in SQL but
> the algorithm applies at the algebra (RelNode) level.
> The API is meant to support optimizations around common table expressions and
> materialized views. For instance, it can be used for workload analysis to
> generate view based recommendations.
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