Enterprise search solutions work on multiple data sources. Integration of these data sources with a search engine is an important aspect of search solution design. The data sources can vary from applications to databases and web crawlers. Like ETL tools of data warehouse, the data loading in search solutions goes through similar cycles. The important part here is how and which data should be loaded in the search engine. In this section, we will look at different approaches while working with the integration of data sources with a search engine. Many times, during the design of a search engine, architects end up using one or more of these data integration patterns for the design. Most application integrations fall under one of the following patterns. Each of them offer unique benefits and drawbacks; the architects have to choose the best-suited pattern based on the landscape.