Konstantin Orlov created IGNITE-25471:
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Summary: Sql. Introduce custom infrastructure for rel explanation
Key: IGNITE-25471
URL: https://issues.apache.org/jira/browse/IGNITE-25471
Project: Ignite
Issue Type: Improvement
Components: sql ai3
Reporter: Konstantin Orlov
Currently, we are taking an advantage of
{{org.apache.calcite.rel.RelNode#explain(org.apache.calcite.rel.RelWriter)}}.
This approach has number of drawbacks.
First, we don't have necessary control over attributers included into printout.
For example, the output of {{TableModify}} node contains attributes
{{sourceExpressionList}} and {{flattened}} which doesn't make sense in our
case. This can be WA'ed by inlining all the explainTerms of parent rel within
{{IgniteTableModify}}, but there is a chance to break serialization in case new
attributes is introduced in upcoming release.
Second, we are resolving indexes into column names, and sometimes you need to
know context to do it properly. For example, {{IgniteMergeJoin}} has
{{leftCollation}} and {{rightCollation}} which must be resolved with lhs or rhs
row type respectively. The context is available in
{{org.apache.ignite.internal.sql.engine.rel.IgniteMergeJoin#explainTerms}}, but
is completely lost in relation-agnostic {{RelWriter}}.
Given that said, it would be beneficial to introduce distinct infrastructure to
printout relations for EXPLAIN command.
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