[SERVER-2235] IndexScan should track the number of calls to seek() and expose in explain Created: 16/Dec/10  Updated: 22/Feb/16  Resolved: 03/Feb/16

Status: Closed
Project: Core Server
Component/s: Querying
Affects Version/s: None
Fix Version/s: 3.3.2

Type: Improvement Priority: Major - P3
Reporter: Aaron Staple Assignee: David Storch
Resolution: Done Votes: 0
Labels: neweng, query_triage
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Documented
is documented by DOCS-7086 Consider documenting "seeks" IXSCAN s... Closed
Related
related to SERVER-10448 Revamp explain() formatting Closed
is related to SERVER-3414 consider using nscannedObjects in add... Closed
Backwards Compatibility: Fully Compatible
Sprint: Query 10 (02/22/16)
Participants:

 Description   

The index scan stage should track the number of calls to BtreeIndexCursor::skip() made here:

https://github.com/mongodb/mongo/blob/r3.0.0-rc6/src/mongo/db/exec/index_scan.cpp#L438-L439

Original Description

Currently nscanned isn't precise enough to distinguish between unindexed traversal and btree traversal, and in some cases between btree skipping and inorder order btree traversal.



 Comments   
Comment by Githook User [ 03/Feb/16 ]

Author:

{u'username': u'dstorch', u'name': u'David Storch', u'email': u'david.storch@10gen.com'}

Message: SERVER-2235 add the number of IXSCAN seeks to explain executionStats output
Branch: master
https://github.com/mongodb/mongo/commit/c8f086a3a52c8793c3f9857cddbff37dc7bcc37d

Comment by David Storch [ 26/Jan/15 ]

Changes to explain made in SERVER-10448 should make it easy to use the totalKeysExamined and totalDocsExamined metrics to distinguish between collection scans and index scans. I am converting this ticket into the second part of this feature request, which is to separately track the number of btree skips so that this can be distinguished from in-order btree traversal.

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