Category Routed Aliases

Through the lifetime of Solr we were given the possibility to work with cores, then collections and finally aliases – the alternative names for collections. Aliases allow the user to give your collection a new, virtual name and group multiple collections under that single virtual name. This allows isolation of the real collection name from the name that the client application is using. That allows changing the collection in the background without the need of bringing down the whole cluster and make your application or product unavailable. In Solr we have the option to use two aliases groups:

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Distributed IDF

When Lucene and Solr searches through the data, each document is assigned a score that is calculated on the basis of query terms statistics. When using SolrCloud and our data inside the collection is distributed among multiple shards we are hit by a problem of not exact inverse document frequency calculation. The problem can be defined in the following way – each shard stores the term statistics locally and doesn’t share that with other shards during query execution. Can we do something about it to have more precise IDF calculation? Let’s see what we can do about it.

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