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https://issues.apache.org/jira/browse/CALCITE-3972?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17101043#comment-17101043
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Julian Hyde commented on CALCITE-3972:
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[~xndai] wrote:
bq. Also the RelBuilder is not immutable today. The stack can change after it's
passed into a function. So it's not a new problem...
I acknowledged that earlier in the comment thread. The stack of {{RelNode}}s
(and ancillary data like aliases) is mutable. The config is not mutable. This
is intentional - I consider config and the rel stack to be different classes of
state.
Any class called 'builder' of course has mutable state. Builders are useful
because they allow mutation in a controlled way.
bq. I mean with the adoptConvention() we create a new builder every time. It
could be problematic if this gets call frequently (such in high frequent rules).
Creating a {{RelBuilder}} is fairly efficient - 7 fields to assign, two object
creations ({{ArrayDeque}} and {{RexSimplify}}). A typical planning process
might fire 10k rules. 10k object creations is not going to move the dial.
> Allow RelBuilder to create RelNode with convention and use it for trait
> convert
> -------------------------------------------------------------------------------
>
> Key: CALCITE-3972
> URL: https://issues.apache.org/jira/browse/CALCITE-3972
> Project: Calcite
> Issue Type: Bug
> Reporter: Xiening Dai
> Assignee: Xiening Dai
> Priority: Major
> Fix For: 1.23.0
>
> Time Spent: 40m
> Remaining Estimate: 0h
>
> 1. Provide Convention.transformRelBuilder() to transform an existing
> RelBuilder into one with specific convention.
> 2. RelBuilder provides withRelFactories() method to allow caller swap the
> underlying RelFactories and create a new builder.
> 3. Use the new interface in RelCollationTraitDef for converting into
> RelCollation traits
> We can avoid ~1/3 of total rule firings in a N way join case with this change.
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