In addition to the PostgreSQL `SQLITE` type, pglite-fusion provides the `query_sqlite`` function for querying SQLite databases and the `execute_sqlite` function for updating them. Additional functions are listed in the project’s README.
The pglite-fusion extension is written in Rust using the pgrx framework [1].
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Implementation Details
The PostgreSQL `SQLITE` type is stored as a CBOR-encoded `Vec<u8>`. When a query is made, this `Vec<u8>` is written to a random file in the `/tmp` directory. SQLite then loads the file, performs the query, and returns the result as a table containing a single row with an array of JSON-encoded values.
The `execute_sqlite` function follows a similar process. However, instead of returning query results, it returns the contents of the SQLite file (stored in `/tmp`) as a new `SQLITE` instance.
We could have SQLite within postgres within sqlite within postgres! Is it practical or even slightly useful? Of course not - but it's SQL databases all the way down. Not that this is a good thing in itself.