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Type: Improvement
Resolution: Unresolved
Priority: Major - P3
Fix Version/s: None
Affects Version/s: None
Component/s: Aggregation Framework
Labels:
- optimization

Assigned Teams:

Query Execution
Backwards Compatibility:
Fully Compatible
Sprint:
Query 10 (02/22/16), Query 11 (03/14/16), Query 12 (04/04/16)
Case:
Confidence Status:
None

Aha! Reference:
None
Tracking Level:
None
Risk Status:
None
Exec Notes:
None
Goal Name:
None
Goal Link:
None

If the input to a $group is sorted by the _id, then only one bucket needs to be maintained at a time. This will reduce memory requirements significantly.

We can examine the _id and take advantage of this if we can force an index scan on the key, if there are no intervening pipeline operations that would affect the results.

depends on

SERVER-4566 In new aggregation framework, $sort, $limit in the pipeline seems loading all the matched data into memory. When we tried to improve the performance by leveraging multi thread aggregation, this makes it much slower than single thread

Closed

is depended on by

SERVER-5795 Very Poor Performances

Closed

SERVER-84466 Complete TODO listed in SERVER-23318

Backlog

is duplicated by

SERVER-41891 $group on sorted cursor forces full collection scan

Closed

SERVER-11447 aggregation can sort using index to speed up group of an indexed field

Closed

SERVER-37242 $group on sort key (after $sort) could be optimized to avoid blocking

Closed

SERVER-21502 $group using index

Closed

is related to

SERVER-2130 Ability to use Limit() with Distinct()

Backlog

SERVER-447 new aggregation framework

Closed

SERVER-29444 Use a covered and streaming plan for $group, $sum:1 queries

Backlog

SERVER-9507 Optimize $sort+$group+$first pipeline to avoid full index scan

Closed

SERVER-21022 Coalesce $group and $limit in aggregation pipeline

Closed

related to

SERVER-4961 $group is taking 2x as long as collection.group()

Closed

SERVER-23477 Aggregation's streaming $group should become blocking when it evaluates an array field in the _id

Closed

SERVER-5361 early $group should provide a hint to use an index matching the group key

Closed

SERVER-20066 Query planner should consider index scans on empty query predicates

Closed

SERVER-40056 Remove disabled partial implementation of streaming $group

Closed

SERVER-55576 Optimize queries on time-series collections which request the most recent value

Closed

(2 is duplicated by, 5 is related to, 6 related to)

Assignee:: [DO NOT USE] Backlog - Query Execution

Reporter:: Daniel Pasette (Inactive)

Participants:: [DO NOT USE] Backlog - Query Execution, Asya Kamsky, Chris Westin, Daniel Pasette, Gavin Price, Githook User, Guido Imperiale, John Watts, Oleg Rekutin, Ramon Fernandez Marina

Votes:: 56 Vote for this issue

Watchers:: 74 Start watching this issue

Created:: Dec 15 2011 11:29:24 PM UTC

Updated:: Jan 09 2024 07:35:26 PM UTC

Confidence Status Last Update:: 10/Feb/16 11:00 PM

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