Solr suggester1/13/2024 One way to improve performance is to reverse the token during indexing which basically changes a leading wildcard query into a trailing wildcard query. If the use case requires leading wildcard queries then there is one trick that can help improve performance. In many cases, there is a better way to handle the query by different tokenization or analyzing. The best way to improve leading wildcard queries is to remove them if possible. This can cause poor caching if the index doesn’t fit in memory as well as other problems. The iteration through the terms cannot stop until it has gone through the entire index for matches. The question mark ( ?) can be significantly more performant since Lucene doesn’t have to check as much. With the asterick ( *) at the beginning of the query, this means that there can be many matches throughout the index. For even moderately sized indices this can be time consuming. When leading wildcards are involved, there is a lot more work that needs to be done since the index is not optimized for this type of lookup.Ī leading wildcard query must iterate through all of the terms in the index to see if they match the query. Lucene is very good at exact matches since it can efficiently query the index for matches. Tokens are the representation of a piece of text data after it has been tokenized and analyzed. Why are leading wildcard queries inefficient?Īpache Lucene, the library that backs Apache Solr and Elasticsearch, is designed to search for tokens. For more details, see the Apache Reference Guide Wildcard Searches page. I am focusing on leading wildcard queries only and not trailing (ie: color:re*) or other combinations (ie: color:*e*). There is another variation where the question mark ( ?) is used as a placeholder for a single character. The asterick ( *) takes the place of one or more characters. For an example, you could look for all colors that end in ed with color:*ed. Leading wildcard queries are term queries that use the asterick ( *) in the beginning of the term. ReversedWildcardFilterFactory Implementation.How to improve leading wildcard queries.Why are leading wildcard queries inefficient?.There are also no references that explain how to verify that leading wildcards are being processed efficiently. It was surprising to me that there are few references explaining what leading wildcard queries are and how they are implemented behind the scenes. There have been many questions over the years about leading wildcard queries. Recently, I was looking into performance where the query had leading wildcards. Apache Solr is a full text search engine that is built on Apache Lucene.
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