what is idhack

[Sameer Akhtar]

Hi All,
I am getting the following result on running the profiler. Can anyone
please let me know that what does 'idhack' mean.

> db.system.profile.find({millis:{$gt:5}})

{ "ts" : ISODate("2011-10-11T14:07:27.361Z"), "info" : "query collider-
server.partners ntoreturn:1 idhack reslen:168 165ms", "millis" :
165 }
{ "ts" : ISODate("2011-10-11T14:07:27.361Z"), "info" : "query collider-
server.partners ntoreturn:1 idhack reslen:168 144ms", "millis" :
144 }
{ "ts" : ISODate("2011-10-11T14:07:27.361Z"), "info" : "query
xyz.partners ntoreturn:1 idhack reslen:168 140ms", "millis" : 140 }
{ "ts" : ISODate("2011-10-11T14:07:27.361Z"), "info" : "query xyz-
server.partners ntoreturn:1 idhack reslen:168 93ms", "millis" : 93 }
{ "ts" : ISODate("2011-10-11T14:07:27.361Z"), "info" : "query xyz-
server.partners ntoreturn:1 idhack reslen:168 62ms", "millis" : 62 }
{ "ts" : ISODate("2011-10-11T14:07:27.361Z"), "info" : "query xyz-
server.partners ntoreturn:1 idhack reslen:168 157ms", "millis" :
157 }
{

[Scott Hernandez]

It just means that the _id index is used and the normal check against
possible indexes is skipped for the special case of a query on the _id
field. It is harmless, and just informational.

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[Karl Seguin]

You mean it short circuits figuring out which query plan will be best, since obvious the index on _id will be?

I've seen that message too...low priority, but I'd say a different message in the log might be better...like "quickId"  or "queryById"

"hack" makes me think you committed something drunk on new years eve.

[Scott Hernandez]

Yes, it does a fast index selection for the _id index.

Feel free to add a jira issue with that comment :)

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