Make query!() recognize Vec<Vec<u8>> as a type

[augustocdias]

I'm trying to batch a insert of multiple rows with the following query (PostgreSQL):

INSERT INTO instances (instance_hash, workflow_hash)
     SELECT i, w FROM unnest($1::BYTEA[], $2::BYTEA[]) as x(i,w)
ON CONFLICT (instance_hash) DO NOTHING

I'm getting the following error: unsupported type BYTEA[] for param #1

I'm using the query! macro to do it and check the query. Is there a way to do it without doing it unchecked?

[abonander]

@augustocdias it's not exactly optimal but you could pass hex encoded strings in and decode them in Postgres:

INSERT INTO instances (instance_hash, workflow_hash)
     SELECT decode(i, 'hex'), decode(w, 'hex') FROM unnest($1::TEXT[], $2::TEXT[]) as x(i,w)
ON CONFLICT (instance_hash) DO NOTHING

We already have trait implementations for Vec<Vec<u8>>, &[&[u8]], Vec<&[u8]> and &[Vec<u8>], it just needs to be enabled in the macros.

Unfortunately though it's only possible to specify one or two types for the macros to use, an "owned" type and a "borrowed" type. Which ones would be the most useful here? You might think Vec<Vec<u8>> and &[&[u8]] but the latter can only be created by constructing an array or vec of slices which is somewhat redundant.

Thus, I would argue that it should be Vec<Vec<u8>> | &[Vec<u8>] which should be added here (and also mirrors Vec<String> | &[String] above which has the same issue): https://github.com/launchbadge/sqlx/blob/master/sqlx-macros/src/database/postgres.rs#L78

When the const_panic feature is stabilized we can get rid of the owned/borrowed distinction and just specify a single type and have a const is_compatible() assertion for borrowed types, which would also significantly improve the typechecking code and the errors it gives.

[augustocdias]

It seems to be as simple as you described. I created the PR for that.

Tks