[SERVER-14929] Performance regression in Queries.FindProjectionDottedField Created: 17/Aug/14  Updated: 02/Jun/15  Resolved: 02/Jun/15

Status: Closed
Project: Core Server
Component/s: Querying
Affects Version/s: 2.6.4
Fix Version/s: None

Type: Bug Priority: Major - P3
Reporter: Alvin Richards (Inactive) Assignee: David Daly
Resolution: Won't Fix Votes: 0
Labels: 28qa
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Depends
Backwards Compatibility: Fully Compatible
Operating System: ALL
Steps To Reproduce:

With a 2.7.1 or greater shell

var tests=[]
load ('/home/alvin/mongo-perf-current/util/utils.js')
tests.push( { name: "Queries.FindProjectionDottedField",
              pre: function( collection ) {
                  collection.drop();
                  for ( var i = 0; i < 1000; i++ ) {
                      collection.insert( { x : { y: i } } );
                  }
              },
              ops: [
                  { op: "find",
                    query: { },
                    filter: { 'x.y' : 1, _id : 0 } }
              ] } );

Sprint: CAP - 3.1.4
Participants:

 Description   

2.5.4 introduced a performance regression for Queries.FindProjectionDottedField over 2.4.10 which still exists in 2.6.4.



 Comments   
Comment by David Daly [ 02/Jun/15 ]

This regression happened as part of a large rewrite of the query system (SERVER-10026). The bad commit was when the new code was turned on (i.e., not a small point change), and there's a previous commit comment about projection being disabled for a period before. Given the amount of change to the query code during that period, and the age of the ticket, closing it.

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