Strategies for using alternative queries to mitigate zero results and their application to online marketplaces

René Kriegler and Jean Silva • Location: TUECHTIG • Back to Haystack EU 2023

We make great efforts to avoid returning an empty search result list to our users. Badly handled zero results queries not only provide a bad user experience but they can also impact our business negatively. On classified ads platforms, like Wallapop, this problem is even more salient as the content is user-generated and as the range of tradable items is almost unbounded and the users come from very diverse backgrounds. The recent developments in vector search and the availability of powerful language models for semantic search seem to solve the problem: we could always return some results. On the other hand, it can often be unclear to the user why a certain result shows up in the results when it comes from vector search. In addition, it would be hard to justify the permanent computational effort to vectorize millions of documents for classified ads that have a very short lifespan. Following up on the strategies for query relaxation that were presented in a talk at Haystack US 2019, we will discuss approaches to providing the user with alternative queries - like query relaxation and query term substitution - that are based on Large Language Models. We will also share our experiments on using simpler approaches to query relaxation that are based on query term statistics. These approaches can provide the user with a better experience and can be used in combination or as a replacement for vector search - not just in the context of a classified ads platform.

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René Kriegler

OpenSource Connections

René has worked in search for almost 16 years, including on projects for some of the top 10 German e-commerce sites. He is co-founder and co-organiser of MICES (Mix-Camp E-commerce Search), an event that brings together the e-commerce search community each year. He created and maintains the Querqy open source library for query rewriting. René is co-initiator of the Chorus project – an open source software stack that combines Querqy with other powerful tools to build e-commerce search and to measure and improve search quality. He works as Director E-commerce at OpenSource Connections.

Jean Silva


Jean Silva is a senior software engineer at Wallapop who has been working with various programming languages since 2008. He fell in love with the search world in 2014 and has never stopped learning and applying his knowledge since. Jean has worked in different industries such as travel, e-commerce, and classified listings.