[DRILL-491] Support project push-down into scan operator

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.4.0
• Assignee: Jinfeng Ni
• Reporter: Jinfeng Ni
• Created: 08/Apr/14 00:29
• Updated: 31/Jul/14 06:32
• Resolved: 04/May/14 16:58

Description

Currently, the scan operator will read all the columns from the data source, and pass all the columns to down-stream operator.

In order to improve performance of Drill query, we should instead push the project operation into scan operator. The scan operator will take as an input a list of columns required to retrieve. If the query only refers a subset of columns, the scan operator will only have to retrieve values for the column in the list.

It's expected to see performance improvement once project push-down is supported.

Issue Links

• is broken by: DRILL-631 Trivial project removal with pushdown breaks information schema