wp-sqlite-db VS parser

Before they added SQLite as WP plugin, I would use https://github.com/aaemnnosttv/wp-sqlite-db/ and I would use `define('DB_DIR', '/absolute/custom/path/to/directory/for/sqlite/database/file/');` to define the database location of my choice; I believe they would let users do the same with core support.

They basically took this implementation and just adapted it to coding standards:

https://github.com/aaemnnosttv/wp-sqlite-db

This has been around since some time and is itself a fork of a previous work.

The interesting part is that this drop-in replacement (mostly) already works well, there are a few issues that are related to some quirks in the WordPress core itself, for example: https://github.com/aaemnnosttv/wp-sqlite-db/issues/18

And maybe now they will be fixed.

Author here, here's an in-depth writeup on how this works and why it's useful:

https://make.wordpress.org/core/2022/09/23/client-side-webas...

To answer your questions directly:

WebAssembly is the magic sauce that transforms server-side code into client-side code. MySQL unfortunately is not yet supported by WebAssembly, so I applied a plugin that adds SQLite supports to WordPress [0]. The WebAssembly application has its own in-memory filesystem that lives in a specific browser tab and is scraped as soon as you close it.

So – technically it exposes db credentials, and even the entire DB, but that you are the only user of that DB so it's okay.

> What would the backend look like

The only backend is a static file server where the code and the database live. Your browser downloads a copy of the database and allows you to modify it in the current tab, but the updates are never saved back to the server.

[0] https://github.com/aaemnnosttv/wp-sqlite-db

1. Plugins that register their own database tables (however there already exists prior art such as https://github.com/aaemnnosttv/wp-sqlite-db for handling these cases)

2. Plugins that do direct queries against the standard database schema (broadly either for invalid (bad code) or performance (valid but slim use case) reasons)

Also, WordPress would of course keep the old query functions around and they would likely add a tag to the plugin repository so authors can mark plugins as supporting thes new ORM features.

Great idea in my opinion!

There's a WordPress plugin that adds support for SQLite as an alternative to MySQL.

Apparently it works really well. The implementation is (to my) simply astonishing: they run regular expressions against the SQL to convert it from MySQL dialect to SQLite! https://github.com/aaemnnosttv/wp-sqlite-db/blob/9a5604cce13...

This wp-sqlite-db one. Not super active, but maintained, at least.

For MySQL the situation is a bit different. sqlc uses the parser of TiDB (https://github.com/pingcap/parser), which is a parser that aims to be basically compatible with MySQL, but is quite young and is not a MySQL parser. The most basic queries work, but even simple joins or aggregations usually result in variables with unknown data types or wrong nullability. So you loose a lot of the benefits of sqlc. Manual type annotations for MySQL also do not work most of the time. They are simply ignored and forwarded to MySQL as invalid query if they do not occur on a place where sqlc is expecting them.

This is a disaster waiting to happen. Regular expressions should never be used to parse non-regular languages, of which SQL is one.

There are a variety of mature MySQL dialect parsers available[1][2], and MySQL should have its own public APIs for transforming a query into an AST. Any of those would be a safer and more correct alternative.

[1]: https://github.com/pingcap/parser

[2]: https://github.com/square/mysql-parser

Pingcap parser is a MySQL parser in Go.