$graphLook enquiries regarding memory consumption

Hi Jose

From the $graphLookup documentation: “The $graphLookup stage must stay within the 100 megabyte memory limit. If allowDiskUse: true is specified for the aggregate() operation, the $graphLookup stage ignores the option”

My understanding is that this means setting allowDiskUse makes no difference to this stage and it still needs to stay within the 100MB limit?

Conversely, In chapter 3, under the general considerations for this stage, Norberto mentions at about 0:40 that allowDiskUse will be helpful to manage documents that exceed the limit

I’m struggling to reconcile both statements. Any further explanation will be appreciated

Regards,
Dayo

Hi,

You are right. $graphLookup ignores the allowDiskUse option, indeed there’s an open ticket to implement this.

https://jira.mongodb.org/browse/SERVER-23980

José Carlos

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