[CASSANDRA-789] Add configurable range sizes, paging to hadoop range queries

• Type: Improvement
• Status: Resolved
• Priority: Low
• Resolution: Fixed
• Fix Version/s: 0.6
• Assignee: Johan Oskarsson
• Reporter: Jonathan Ellis

Authors

Johan Oskarsson

• Created: 12/Feb/10 21:32
• Updated: 16/Apr/19 09:33
• Resolved: 17/Mar/10 15:36

Description

For very large (billions) numbers of keys, the current hardcoded 4096 keys per InputSplit could cause the split generator to OOM, since all splits are held in memory at once. So we want to make 2 changes:

1) make the number of keys configurable*
2) make record reader page instead of assuming it can read all rows into memory at once

Note: going back to specifying number of splits instead of number of keys is bad for two reasons. First, it does not work with the standard hadoop mapred.min.split.size configuration option. Second, it means we have no way of measuring progress in the record reader, since we have no idea how many keys are in the split. If we specify number of keys, then even if we page we know (to within a small margin of error) how many keys to expect, even if we page.

See CASSANDRA-775, CASSANDRA-342 for background.

Sub-Tasks

• Add method to set Hadoop InputSlit sizes: Resolved