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From "Michael J. Carey (Jira)" <>
Subject [jira] [Assigned] (ASTERIXDB-2913) Need "break up to make up" rewrite rule for unnested data
Date Mon, 14 Jun 2021 04:13:00 GMT


Michael J. Carey reassigned ASTERIXDB-2913:

    Assignee: Dmitry Lychagin

> Need "break up to make up" rewrite rule for unnested data
> ---------------------------------------------------------
>                 Key: ASTERIXDB-2913
>                 URL:
>             Project: Apache AsterixDB
>          Issue Type: Bug
>            Reporter: Michael J. Carey
>            Assignee: Dmitry Lychagin
>            Priority: Major
> Consider the following query using the Don Chamberlin book data:
> _USE DonCData;_ 
> _WITH flat_orders AS (SELECT orderno, custid, order_date, ship_date FROM orders),_
>            _flat_items AS (SELECT o.orderno, i.* FROM orders o, o.items i)_
> _SELECT fo.*, fi.* FROM flat_orders fo, flat_items fi_
> _WHERE fo.orderno = fi.orderno;_
> Right now this query leads to two scans of orders - one for flat_orders and one for flat_items
- followed by a join of the two.
> It seems like it should be possible to rewrite (under the hood) this query as simply:
> _USE DonCData;_ 
> _SELECT o.orderno, o.custid, o.order_date, o.ship_date, i.*_
> _FROM orders o, o.items i;_
> This capability could prove super-helpful in our future BI story.  (Picture two flat
views being exported for JDBC - it would be nice to be able to piece them back together for
efficient querying under the hood.)

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