Improved project pushdown for optiq-csv

[Bruno Dumon]

Hi,

The ProjectRel pushdown rule in the csv sample can only handle simple field selections. I tried to make an improved version that should be able to handle any query, my changes are here:

https://github.com/bdumon/optiq-csv/commit/4cf861b243984ad0e1f623990bb78f8dc0559033

I'm not sure if this is suited to be included in the csv sample since it is a bit more complex (but not that much actually). Anyhow, this might be useful to someone else learning this stuff, and I also welcome any feedback as to whether I approached this the right way.

Bruno.

[Vladimir Sitnikov]

This is great. Thank you for sharing.

I've tried it in a similar case and it just works. Amazing.

PS. It is hard to understand how all those toRel/Enumerable/Project/Trait things cooperate when you face optiq for the first time.

When I've opened optiq-csv, I could not pass through all those stuff, and there was no solid picture why need so RelType/Scan/Rule/etc stuff.

However optiq-csv is usable as a starter for learning/trying optiq.

I believe, it makes sense to include some step-by-step description (e.g. sequence diagram).

[Damien Carol]

It would be great to add it to the tutorial of optiq-csv.

[Julian Hyde]

I think it would make sense to have this as an additional rule, or maybe replace the existing pushdown rule. It really depends on what is more helpful for people learning optiq. That is the purpose of optiq-csv, after all.

Bruno,

Can you please create a pull-request for this? Otherwise I'll forget to look at it.

Julian

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[Vladimir Sitnikov]

I've opened a JIRA case at https://issues.apache.org/jira/browse/CALCITE-477

Welcome to Calcite JIRA and/or dev @ calcite.incubator.apache.org and/or https://github.com/apache/incubator-calcite

Vladimir