[jira] [Assigned] (CALCITE-3923) Refactor how planner rules are parameterized

["Julian Hyde (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CALCITE-3923?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Julian Hyde reassigned CALCITE-3923:
------------------------------------

    Assignee: Julian Hyde

> Refactor how planner rules are parameterized
> --------------------------------------------
>
>                 Key: CALCITE-3923
>                 URL: https://issues.apache.org/jira/browse/CALCITE-3923
>             Project: Calcite
>          Issue Type: Bug
>            Reporter: Julian Hyde
>            Assignee: Julian Hyde
>            Priority: Major
>
> People often want different variants of planner rules. An example is {{FilterJoinRule}}, which has a 'boolean smart’ parameter, a predicate (which returns whether to pull up filter conditions), operands (which determine the precise sub-classes of {{RelNode}} that the rule should match) and a {{RelBuilderFactory}} (which controls the type of {{RelNode}} created by this rule).
> Suppose you have an instance of {{FilterJoinRule}} and you want to change {{smart}} from true to false. The {{smart}} parameter is immutable (good!) but you can’t easily create a clone of the rule because you don’t know the values of the other parameters. Your instance might even be (unbeknownst to you) a sub-class with extra parameters and a private constructor.
> So, my proposal is to put all of the config information of a {{RelOptRule}} into a single {{config}} parameter that contains all relevant properties. Each sub-class of {{RelOptRule}} would have one constructor with just a ‘config’ parameter. Each config knows which sub-class of {{RelOptRule}} to create. Therefore it is easy to copy a config, change one or more properties, and create a new rule instance.
> Adding a property to a rule’s config does not require us to add or deprecate any constructors.
> The operands are part of the config, so if you have a rule that matches a {{EnumerableFilter}} on an {{EnumerableJoin}} and you want to make it match an {{EnumerableFilter}} on an {{EnumerableNestedLoopJoin}}, you can easily create one with one changed operand.
> The config is immutable and self-describing, so we can use it to automatically generate a unique description for each rule instance.
> (See the email thread [[DISCUSS] Refactor how planner rules are parameterized|https://lists.apache.org/thread.html/rfdf6f9b7821988bdd92b0377e3d293443a6376f4773c4c658c891cf9%40%3Cdev.calcite.apache.org%3E].)



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