Thomas Ardal

Freelance software consultant and entrepreneur building SaaS applications like elmah.io

Implementing date histogram facets with ElasticSearch and NEST

My pet project elmah.io stores every error in Elasticsearch and the search GUI contains a perfect example for doing faceted search: the errors graph in top of the search result.

errors_per_day

At the moment the code for this sucker isn’t the stuff I’m most proud of. I simply extract every error created during the last 14 days and doing some LINQ to Objects magic on top of that. Not really optimal. What I really want to do, is letting Elasticsearch create a date histogram containing a dictionary of values where the date is key and the amount of errors created on that date as value. The query turned out to be really simple, once I got a hang on faceted search using NEST (the excellent .NET client for Elasticsearch):

Thanks to Martijn Laarman for the help on StackOverflow.

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