Modern desktop applications typically deal with a significant number of files. Most applications and utilities have one or more preference files. There may also be system-wide and per-user configuration files, caches, and other data that must be tracked and stored. Document-based applications also need to store and access the actual document files.
Using the SQLite library as an abstract storage layer has many advantages. A fair amount of application metadata, such as caches, state data, and configuration data, fit well with the relational data model. This makes it relatively easy to create an appropriate database design that maps cleanly and easily into an application’s internal data structures.
In many cases, SQLite can also work well as a document file format. Rather than creating a custom document format, an application can simply use individual database instances to represent working documents. SQLite supports many standard datatypes, including Unicode text, as well as arbitrary binary data fields that can store images or other raw data.
Even if an application does not have particularly strong relational requirements, there are still significant advantages to using the SQLite library as a storage container. The SQLite library provides incremental updates that make it quick and easy to save small changes. The transaction system protects all file I/O against process termination and power disruption, nearly eliminating the possibility of file corruption. SQLite even provides its own file caching layer, so that very large files can be opened and processed in a limited memory footprint, without any additional work on the part of the application.
SQLite database files are cross-platform, allowing easy migration. File contents can be easily and safely shared with other applications without worrying about detailed file format specifications. The common file format also makes it easy for automated scripts or troubleshooting utilities to access the files. Multiple applications can even access the same file simultaneously, and the library will transparently take care of all required file locking and cache synchronization.
The use of SQLite can also make debugging and troubleshooting much easier, as files can be inspected and manipulated with standard database tools. You can even use standard tools to inspect and modify a database file as your application is using it. Similarly, test files can be programmatically generated outside the application, which is useful for automatic testing suites.
Using an entire database instance as a document container may sound a bit unusual, but it is worth considering. The advantages are significant and should help a developer stay focused on the core of their application, rather than worrying about file formats, caching, or data synchronization.