[HADOOP-13368] DFSOpsCountStatistics$OpType#fromSymbol and s3a.Statistic#fromSymbol should be O(1) operation

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.8.0
• Fix Version/s: 2.8.0, 3.0.0-alpha1
• Component/s: fs
• Target Version/s: 2.8.0
• Hadoop Flags: Reviewed
• Assignee: Mingliang Liu
• Reporter: Mingliang Liu
• Created: 12/Jul/16 22:18
• Updated: 30/Aug/16 01:12
• Resolved: 15/Jul/16 22:20

Description

To lookup, DFSOpsCountStatistics$OpType#fromSymbol and s3a.Statistic#fromSymbol iterates all the enums to get the entry by its symbol. Usages of fromSymbol() include isTracked() and getLong().

As there are dozens of enum entries, it merits to make these two similar operations O(1) complexity. This point is especially true if downstream app probes a dozen of stats in an outer loop (see TEZ-3331).