[DRILL-4287] Do lazy reading of parquet metadata cache file

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.4.0
• Fix Version/s: 1.6.0
• Component/s: Query Planning & Optimization
• Assignee: Aman Sinha
• Reporter: Aman Sinha
• Reviewer: dgu-atmapr
• Created: 19/Jan/16 23:50
• Updated: 13/Apr/16 20:49
• Resolved: 16/Mar/16 23:59

Description

Currently, the parquet metadata cache file is read eagerly during creation of the DrillTable (as part of ParquetFormatMatcher.isReadable()). This is not desirable from performance standpoint since there are scenarios where we want to do some up-front optimizations - e.g. directory-based partition pruning (see DRILL-2517) or potential limit 0 optimization etc. - and in such situations it is better to do lazy reading of the metadata cache file.

This is a placeholder to perform such delayed reading since it is needed for the aforementioned optimizations.