Add postgres range type

[jonasrichard]

PR Info

• Closes Question: support for range types #69

New Features

• Provide a new type RangeType to implement Postgres range type
• Provide range type as an element type of Postgres Array

Doubts

• Not sure where to implement hashable-value features. I put that in the with_range.rs
• It implements time ranges with Chrono and Time I left out Jiff now
• Not sure how it plays together with with-json
• How to make RangeType from std Rust types (tuple, std range, how to describe exclusive and inclusive bounds?)
• A refactor PR is going on which may affect this branch (Refactor Value::Array and add Value::Enum #1004)

[jonasrichard]

The current dilemma is that I need to implement ToSql but in with_range.rs in src, because I think I cannot implement that in sea-query-postgres trait.

[tyt2y3]

i see, shall we move that to a separate type crate? something like sea-query-types / sea-query-postgres-types?

[jonasrichard]

I will create a create for postgres only now, so the 2nd. And addressing the sea-query-sqlx compilation error.

[tyt2y3]

sounds good, thank you! I will take a closer look

[jonasrichard]

@tyt2y3 I started to move Range to the sea-query-postgres-types crate but I am struggling a bit.

• I cannot reach this crate from the root crate sea-query. I think I would like to re-export these two types from sea-query-postgres crate and that crate is enough to be visible from sea-query.
• Another one, I tried to put a serde feature - because it is needed by the type definition - in the Cargo.toml of sea-query-postgres-types and say: use the same features as the root crate. Hope it is correct.
• I included serde in types crate as well, I feel that it is a duplication to say the serde version twice (this and in the root crate).

If you can tell me what to change to fix the 1st point I can go on.

[tyt2y3]

thank you. the problem is sea-query-postgres depends on sea-query so it won't work due to circular dependency.
the crate dependency graph should be:

1. sea-query-postgres-types: defines Range and implement ToSql for it (behind a feature flag driver-postgres)
2. sea-query-postgres: depends on sea-query-postgres-types and turn on the feature flag
3. sea-query: depends on sea-query-postgres-types but not turn on the feature flag

dont worry if you can't get CI to pass 100%, I will be able to fix that

I included serde in types crate as well, I feel that it is a duplication to say the serde version twice (this and in the root crate).

this is un-avoidable so I'll set one of them to a very loose requirement, i.e. version = "1"

[jonasrichard]

The next obstactle is how to implement ToSql. It seems that sqlx::PgRange<T> implements Encode rather, and all the constituent types (like i32 range, i64 range, etc) needs to implement Encode.

https://docs.rs/sqlx/latest/sqlx/postgres/types/struct.PgRange.html#impl-Encode%3C'q,+Postgres%3E-for-PgRange%3CT%3E

I don't think this goes to a good direction, though.

The other option is to implement the ToSql trait with using postgres-protocol, which used by postgres-types.

https://docs.rs/postgres-protocol/latest/postgres_protocol/types/enum.Range.html

Although I need to figure out how to construct that value for the sake of conversion. Because it has a lifetime and I don't want to have a RangeType with lifetimes.

Also I am leaning toward the generic RangeType implementation, and during ToSql conversion we can restrict the types we accept. So we will have 6 different impl block like impl ToSql for RangeType<i32> and so on.

[jonasrichard]

Finally I implemented by postgres-protocol so we don't need to sqlx type.

[jonasrichard]

Okay, I think I am ready with that. I managed to run almost all checks with build-tools/rustclippy.sh

[jonasrichard]

The next obstactle - quite a big one - is to implement sqlx::Encode with RangeType.

The problem is that in sea-query-sqlx we either make a PgRange conversion, which is not possible since our Value type is not generic. Or we need to implement Encode trait by hand in sea-query-postgres-types which is not easy since all the supporting types are private in sqlx.

https://docs.rs/sqlx-postgres/0.8.6/src/sqlx_postgres/types/range.rs.html#291-293

I think this is the last step since other cases I feel are covered.

[tyt2y3]

thank you for the great work so far! for you personal use case, do you use postgres or sqlx?

[jonasrichard]

I started to use this for a postgres database for a proof of concept, but to be honest I just wanted to contribute to know better Rust.

[tyt2y3]

thank you! if this works for you let's get this merged for now.
can create a followup PR for SQLx.

I think the strategy is to convert our own RangeType to sqlx's Range on the fly and call bind()

[tyt2y3]

I've pushed some commits to adjust the crate structure