[SERVER-19578] Adding showDiskLoc unnecessarily fetches document Created: 24/Jul/15  Updated: 06/Dec/22

Status: Backlog
Project: Core Server
Component/s: Querying
Affects Version/s: 3.0.4
Fix Version/s: None

Type: Improvement Priority: Major - P3
Reporter: Bruce Lucas (Inactive) Assignee: Backlog - Query Execution
Resolution: Unresolved Votes: 1
Labels: query-44-grooming
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Assigned Teams:
Query Execution
Participants:

 Description   

While investigating an index corruption case, I enountered the following:

The following query failed because the index pointed to a bad location. That is the issue I was investigating, not the problem I'm reporting on this ticket.

db.c.find(q).next()

This query succeeds because it is covered so avoids attempting to fetch the document at the bad location:

db.c.find(q, {_id:1}).hint({_id:1}).next()

Now attempt to determine the bad location by using showDiskLoc(); it unexpectedly fails attempting to fetch the document (verified by the stack trace), even though it should also be covered:

db.c.find(q, {_id:1}).hint({_id:1}).showDiskLoc().next()


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