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https://issues.apache.org/jira/browse/CALCITE-2470?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16624802#comment-16624802
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Vladimir Sitnikov commented on CALCITE-2470:
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[~julianhyde], {{shouldMergeProject}} is really hard to use.
Note: org.apache.calcite.tools.PigRelBuilder extends RelBuilder, however
PigRelBuilder is placed in exactly the same package as
org.apache.calcite.tools.RelBuilder.
It will cause split-packages kind of issue (the same package name is reused for
different jars).
Note: {{relBuilder.cluster}} and {{relBuilder.relOptSchema}} are NOT accessible
from a derived class that is located in different package.
> RelBuilder.project should combine expressions if underlying node is a Project
> -----------------------------------------------------------------------------
>
> Key: CALCITE-2470
> URL: https://issues.apache.org/jira/browse/CALCITE-2470
> Project: Calcite
> Issue Type: Bug
> Reporter: Julian Hyde
> Assignee: Julian Hyde
> Priority: Major
> Fix For: 1.18.0
>
>
> The {{RelBuilder.project}} method should combine expressions if underlying
> node is a {{Project}}.
> For example, if {{r}} is a {{RelBuilder}} and its stack initially contains
> {code:java}
> Project(Scan(T), a, b, a + b as c){code}
> and we call (in pseudo-code)
> {code:java}
> r.project(a + c as d){code}
> then the result should be
> {code:java}
> Project(Scan(T), a + (a + b) as d){code}
> Today the result is
> {code:java}
> Project(Project(Scan(T), a, a + b as c), a + c as d){code}
> In some circumstances the result will be larger (i.e. contain more
> {{RexNode}} instances) but much more frequently the result will be smaller
> and simpler.
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