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https://issues.apache.org/jira/browse/CALCITE-828?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14910108#comment-14910108
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Julian Hyde commented on CALCITE-828:
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I have completed work in the branch. Can someone please review?
> Use RelBuilder in rules rather than type-specific RelNode factories
> -------------------------------------------------------------------
>
> Key: CALCITE-828
> URL: https://issues.apache.org/jira/browse/CALCITE-828
> Project: Calcite
> Issue Type: Bug
> Reporter: Julian Hyde
> Assignee: Julian Hyde
>
> Many planner rules create filters, projects, joins, ... and over the years
> people have made them generic, so they can create different particular
> sub-classes of RelNodes (say DrillFilter or HiveProject) by adding factories
> (interfaces defined in RelFactories).
> But then people extend a rule, so that a rule that used to only create
> projects now might sometimes create a filter. They now need to add an extra
> parameter to the instance of the rule, which is painful. Also, rules may call
> into utility methods such as RelOptUtil.pushDownJoinConditions (see
> CALCITE-826), which have similar problems.
> The solution is to get rid of factories in public interfaces and instead pass
> around a RelBuilder. A particular instance of RelBuilder has a factory inside
> it for each type of RelNode. In general a particular client of Calcite (e.g.
> Hive) will be able to use the same RelBuilder throughout a query.
> Rules are static, so a rule instance cannot contain a RelBuilder, only a
> ProtoRelBuilder, which can create a RelBuilder given a RelOptCluster and
> RelOptSchema.
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