SQL Databases are the standard tool for manipulating relational data with ACID transactions, but they are not convenient to use from C++. Raw SQL APIs such as SQLite do not match the C++ programming paradigm well: queries are strings parsed at run time, and the API is not type-safe. An ORM or a template library such as sqlpp11 can hide SQL from the C++ code, and improve type safety, but such a solution only adds a layer on top of string manipulation, and does not remove it.
In many applications, the immense complexity of a SQL database is not at all necessary. Joedb is a minimalist low-level alternative that can perform ACID transactions, on a local database or over a network connection. As shown in the diagram below, joedb compiles the database schema into C++ code. Applications using this code can then manipulate data like a C++ container, with compile-time checking of field names and types:
Other systems such as protocol buffers provide similar type-safe mechanisms for serializing structured data, but are missing key properties of a database, such as concurrency, transactions, and incremental crash-safe updates. Joedb can offer all these features by storing data as a journal of transactions. The whole data history is stored, so it is possible to re-create any past state of the database. Joedb also has a network protocol, and can operate a bit like git for structured data.
To give an indication of joedb's simplicity, the table below shows the size of
joedb's source code compared to some other libraries. Lines of code are counted
with wc -l. Compressed size is the size in bytes after removing comments
and compressing with gzip. These numbers were measured on 2024-07-28 on the
main branch.
| Software | Lines of code | Compressed size | Notes |
|---|---|---|---|
| joedb | 19,288 | 72,268 | without tests |
| nlhohmann/json | 24,941 | 87,168 | single include |
| boost/json | 37,609 | 123,229 | |
| SQLite | 258,281 | 1,067,983 | sqlite3.c amalgamation |
| PostgreSQL | 1,513,329 | 5,250,316 | content of src dir, without tests |
So joedb is an extremely simple low-level foundation for sharing relational data. It would be possible to build a SQL database on top of it, but it is already very convenient by itself.
For more information, please take at a look at the documentation.