Custom backend resources/outline?

[markalexander]

Hi,

I'd like to get Diesel working for e.g. ClickHouse projects and was wondering:

(a) What's the general amount of work involved in making a custom connection + backend? Can I just implement any arbitary subset of the dialect to meet my needs, or does Diesel require a certain coverage of implementation to work at all?

(b) Are there any third party backend crates out there that are considered 'good' implementations and that I can take a look at?

Thanks!

[weiznich]

(a) What's the general amount of work involved in making a custom connection + backend? Can I just implement any arbitary subset of the dialect to meet my needs, or does Diesel require a certain coverage of implementation to work at all?

There is some general documentation on that topic here and here. You need to implement most of the traits listed there to get basic functionality. You need at least LoadConnection, Connection, Backend, SqlDialect, all the HasSqlType’, FromSqlandToSqlimpls. Likely you also needBindCollectorandQueryBuilderif you cannot use and existing one. Depending on the choices you make while implementing them (especiallySqlDialectandHasSqlType`) additional impls might be required to fine tune the generated sql and type mapping. Overall I would expect that you need something about 1k lines of rust code to get something up and running. On the bright side, given no super exotic SQL dialect that will already be quite complete and useable. The details obviously heavily depend on which interface you can use to program against.

Are there any third party backend crates out there that are considered 'good' implementations and that I can take a look at?

I'm aware of the following third party backends:

• diesel-oci
• rsfbclient-diesel
• diesel-mssql

Also the in tree backends/connections can serve as and example. diesel-async can serve as example how to only use a partial set of the traits listed above and replace others with different (but conceptually similar) interfaces.

I hope that gives you at least a clue where to start. Otherwise I'm also happy to provide pointers for specific problems as long as the code is open source.

[markalexander]

Thanks! This is very helpful as a jumping-off point.