PHOENIX-4311: Unnest Support

[tricolor2]

I have started the implementation of the UNNEST function support. I've implemented similarly to Postgresql. So far I can perform a select, aggregations, use limit, upsert using it.

My next step is to implement the Where compiler to create a post-filter for the UNNESTED column but I need your feed back on what is implemented so far before doing so.

Missing components are:

• WHERE compiler
• JOIN support

Improvements:

• Add to the explain plan the UNNEST columns
• Add the post-unnest filter information to the plan when the where will be implemented
• Return a ProjectedColumnExpression column instead of KeyValueColumnExpression to save bandwidth

Best regards,

[tricolor2]

At the moment I will not add the support in the views and subqueries. We are not using the views Eventual we might implement the subqueries support. It would be nice to have a row operation instead of a column opperation. I'm waiting for your comments.

[dbwong]

@tricolor2 Okay, I'll take a look. On my brief survey it wasn't apparent where you were disalllowing the unnest to appear for example in Subqueries.