[PHOENIX-1779] Parallelize fetching of next batch of records for scans corresponding to queries with no order by

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 4.4.0
• Assignee: Samarth Jain
• Reporter: Samarth Jain
• Created: 26/Mar/15 19:18
• Updated: 21/Nov/15 02:18
• Resolved: 17/Apr/15 19:48

Description

Today in Phoenix we parallelize the first execution of scans i.e. we load only the first batch of records up to the scan's cache size in parallel. Loading of subsequent batches of records in scanners is essentially serial. This could be improved especially for queries, including the ones with no order by clauses, that do not need any kind of merge sort on the client. This could also potentially improve the performance of UPSERT SELECT statements that load data from one table and insert into another. One such use case being creating immutable indexes for tables that already have data. It could also potentially improve the performance of our MapReduce solution for bulk loading data by improving the speed of the loading/mapping phase.

Issue Links

• relates to: PHOENIX-1871 Optimize Union All by fetching in parallel batches of records for *all* the underlying scanners