[SERVER-4717] consider removing fast count mode, otherwise refactor it Created: 19/Jan/12  Updated: 08/Mar/13  Resolved: 15/Oct/12

Status: Closed
Project: Core Server
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Question Priority: Major - P3
Reporter: Aaron Staple Assignee: Unassigned
Resolution: Done Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Related
is related to SERVER-4529 fast count mode should not be used wh... Closed
is related to SERVER-1752 improve the performance of simple counts Closed
Participants:

 Description   

We have a 'fast' count mode that runs in cases like a query on

{a:'c',b:'d'}

with index

{a:1,b:1}

. (Among other restrictions, all fields of the index must be present and the queried values must not be objects or numbers.) This optimization adds implementation complexity and has been a source of bugs (eg SERVER-4529). Additionally, the performance of this special counting mode has likely been degraded by changes over time (eg SERVER-3449).

Also, I'm not sure if we've actually measured the performance of fast count mode. We might consider removing it, otherwise we might refactor it out of the main query path.



 Comments   
Comment by Aaron Staple [ 15/Oct/12 ]

The old fast count mode will be superseded by SERVER-1752.

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