[MAPREDUCE-875] Make DBRecordReader execute queries lazily

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.21.0
• Hadoop Flags: Reviewed
• Assignee: Aaron Kimball
• Reporter: Aaron Kimball
• Created: 14/Aug/09 23:09
• Updated: 24/Aug/10 21:15
• Resolved: 27/Aug/09 08:43

Description

DBInputFormat's DBRecordReader executes the user's SQL query in the constructor. If the query is long-running, this can cause task timeout. The user is unable to spawn a background thread (e.g., in a MapRunnable) to inform Hadoop of on-going progress.