[DRILL-7763] Add Limit Pushdown to File Based Storage Plugins

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.17.0
• Fix Version/s: 1.19.0
• Assignee: Charles Givre
• Reporter: Charles Givre
• Created: 03/Jul/20 04:15
• Updated: 16/Dec/20 14:25
• Resolved: 16/Dec/20 14:25

Description

As currently implemented, when querying a file, Drill will read the entire file even if a limit is specified in the query.  This PR does a few things:

1. Refactors the EasyGroupScan, EasySubScan, and EasyFormatConfig to allow the option of pushing down limits.
2. Applies this to all the EVF based format plugins which are: LogRegex, PCAP, SPSS, Esri, Excel and Text (CSV). 

Due to JSON's fluid schema, it would be unwise to adopt the limit pushdown as it could result in very inconsistent schemata.