Using versioning

When working with NoSQL solutions such as Solr, we usually don't have the notion of transaction and we can't predict the sequence in which documents will be received by Solr and indexed especially when indexing is done from multiple threads and machines. However, in certain cases, such a functionality is needed at least to some degree. For example, we don't want to run an update on a document that was updated between the time period we read the document and sent the update. This recipe will show you how to avoid such situations.

Getting ready

This recipe uses the functionality discussed in the Updating document fields recipe from Chapter 2, Indexing Your Data. Read this recipe before proceeding.

How to do it...

For the purpose of this recipe, we assume that we have an e-commerce library. When updating prices of the books, we need to read the document to get the current price, update it in the UI, and index the document. However, it can happen that the same book is being updated...