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https://issues.apache.org/jira/browse/CALCITE-2812?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16761557#comment-16761557
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Ruben Quesada Lopez commented on CALCITE-2812:
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[~wmoustafa], we can take for example RelBuilderTest#testRecursiveUnion2() in
the PR. In that test we build a plan to compute the factorial function from 0
to 7, which generates the following tree (RecursiveUnion with Values as "seed"
part and DeltaTableScan + Filter + Project as "recursive" part):
{code}
LogicalRecursiveUnion(all=[true], tableName=[AUX])
LogicalValues(tuples=[[{ 0, 1 }]])
LogicalProject(n=[+($0, 1)], fact=[*(+($0, 1), $1)])
LogicalFilter(condition=[<($0, 7)])
LogicalDeltaTableScan(table=[[AUX]])
{code}
> Add algebraic operators to allow expressing recursive queries
> -------------------------------------------------------------
>
> Key: CALCITE-2812
> URL: https://issues.apache.org/jira/browse/CALCITE-2812
> Project: Calcite
> Issue Type: New Feature
> Components: core
> Affects Versions: 1.18.0
> Reporter: Stamatis Zampetakis
> Assignee: Julian Hyde
> Priority: Major
> Fix For: next
>
>
> In order to parse, optimize, and execute, recursive queries, expressed in
> SQL, datalog, SPARQL, or other high level language we need first to be able
> to represent recursive queries in relational algebra.
> The subject has been previously discussed in the dev list (see thread with
> title [Recursive query, graph query,
> Datalog|http://mail-archives.apache.org/mod_mbox/calcite-dev/201712.mbox/%3CCAPSgeESFyih9_hf9=uMWFN00BCR7sjf0T+FRY2=ary3ygm1...@mail.gmail.com%3E])
> where various ideas and optimizations were proposed.
> In this issue, we attempt to address only the algebraic part providing the
> following:
> # logical operator(s) for expressing recursion;
> # naive physical operator(s) for the Enumerable convention;
> # ability to create a recusive plan using the RelBuilder.
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