[DRILL-7601] Shift column conversion to reader from scan framework

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.17.0
• Fix Version/s: 1.18.0
• Labels: ready-to-commit
• Assignee: Paul Rogers
• Reporter: Paul Rogers
• Reviewer: Arina Ielchiieva
• Created: 25/Feb/20 00:05
• Updated: 11/Mar/20 14:42
• Resolved: 11/Mar/20 14:41

Description

At the time we implemented provided schemas with the text reader, the best path forward appeared to be to perform column type conversions within the scan framework including deep in the column writer structure.

Experience with other readers has shown that the text reader is a special case: it always writes strings, which Drill-provided converters can parse into other types. Other readers, however are not so simple: they often have their own source structures which must be mated to a column reader, and so conversion is generally best done in the reader where it can be specific to the nuances of each reader.

This ticket asks to restructure the conversion code to fit the reader-does-conversion pattern.

Issue Links

• links to: GitHub Pull Request #1993