A Principled Approach to Querying Data – A Type-Safe Search DSL

Summary

The rise of local-first web applications demands a rethinking of traditional client-server architectures. Users expect near-native responsiveness, even when offline. This necessitates efficient, client-side data processing, including search. The techniques presented in this article, while discussed in a local-first context, are equally applicable to server-side systems. We’ll explore a type-driven approach, leveraging a Domain-Specific Language (DSL), to create a powerful and maintainable search system. The complete, dependency-free code for this article is available on GitHub. Domain-Specific Languages (DSLs) Our approach centers around a DSL tailored to the specifics of searching “issues” – a common concept in project management and bug tracking. A DSL provides a specialized language for expressing search intent, offering several key advantages. Consider these example queries: is:open label:bug author:alice (type:feature type:enhancement) is:closed milestone:v1.0 assignee:bob The expressiveness and clarity of a well-designed Domain-Specific Language (DSL) are evident across many successful systems. Examples include Lucene/Elasticsearch, which utilizes a query string DSL for full-text search. SQL employs its WHERE clause as a DSL for filtering data, and GraphQL defines a query language for fetching data from APIs. The reader might observe the similarity of the proposed DSL to the one used by GitHub in their issue search functionality. The benefits of using a DSL are multifaceted. It provides controlled complexity by limiting the scope of possible queries and ensures domain alignment by mirroring the domain’s concepts in its vocabulary. This, in turn, enhances usability, allowing users to query using familiar terms. Furthermore, a formal grammar simplifies maintainability and extensibility, making modification and expansion more manageable. Defining the domain The structure of the dataset is usually inferred from the constraints of the business domain being modeled....