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From Julian Hyde <>
Subject Re: Guidance for writing a Calcite adapter for a deep hierarchical dataset
Date Wed, 08 Oct 2014 19:41:33 GMT
On Oct 8, 2014, at 12:05 PM, Hartman, Trevor <> wrote:

> Ah, aren't MongoDB and JSON both examples of hierarchical datasets?

Yes. You can handle these if you work in “type-less” mode. Each column is a map, which
contains (property, value) pairs, and each value might be regular a value, an array, or another
map. It is very close to the JSON model.

That’s what I’d suggest for your case.

A useful addition would be something like Oracle’s JSON_VALUE function [1], which allows
you to use something like an XPath expression to burrow deep into a nested document.

And by the way, you asked about schemas. Some people use it to mean “the set of columns
and their types in a table”, but we use the term “row type” for that. A calcite schema,
just as in JDBC [2], is a namespace that contains tables. (Similar to a catalog and a database.)
I think you are interested in what we call a row type.


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