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Diesel

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A safe, extensible ORM and Query Builder for Rust48 Servers

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22 Jan 2020
23:17:54@gitter_kosten:matrix.orgKonstantin (Gitter)Thx for help :)
23 Jan 2020
16:25:04@gitter_tobx:matrix.orgtobx (Gitter) Hey, I have some more general questions about Rust and derive. The Diesel examples talk about a Post and a NewPost struct. Post impl Queryable and NewPost impl Insertable. Now, the more my small test application grows, I realize, that I need more and more of thoses structs. E.g. I need some processing between deserialization and insert. So I have a struct DesirializedNewPost that can be converted to a InsertableNewPost. A Post derived from the database has information that are not meant for the user, so I first convert it into a SerializablePost. Furthermore I need a DesirializedPostUpdate and a InsertablePostUpdate struct. So for simple CRUD operations using the recommended derive options this is a lot of structs to define. Am I doing something wrong?
20:13:16@gitter_weiznich:matrix.orgGeorg Semmler (Gitter) @tobx That's not how I would structure the code. You don't need to have separate structs for deriving Queryable and Serialize or for Insertable/AsChangeset and Serialize. The details depend a bit on your exact use case. Normally you would just use the same struct for both derives. If you need to do some pre/postprocessing a combination of using tuples for diesel and #[serde(flatten)] is useful. To bring an simple example here: Supposed you are having some data set that are coming via some json api and you need to add a single field before inserting the data. In that case you would have a struct that derives Deserialize and Insertable and then do something like this: diesel::insert_into(some_table::table).values((your_struct_implementing_insertable, some_table::some_column.eq(something)).execute(&conn). The strategy works similar for updates. For queries normally a combination of custom select clauses and Queryable is sufficient. Otherwise just build a internal struct out of the values you can get from the database and wrap that into an outer struct adding the missing fields. You could just flatten that via #[serde(flatten)].
23:14:33@gitter_tobx:matrix.orgtobx (Gitter)Ok, I think I might have not the optimal database design, I guess with your tips I can improve that to achieve easier code.
24 Jan 2020
00:45:49@gitter_webewizard:matrix.orgWebeWizard (Gitter) joined the room.
00:45:49@gitter_webewizard:matrix.orgWebeWizard (Gitter) Hey all. Fairly new to Diesel, trying to use mysql backend. It seems like operations like '+' are not implemented for mysql Unsigned<T> types. Can anyone confirm? I don't see any open issues related to it
04:50:10@gitter_webewizard:matrix.orgWebeWizard (Gitter) trying to use it in update/set .set(CardDSL::deck_pos.eq(CardDSL::deck_pos + 1)) where deck_pos is an Unsigned<Smallint>
05:32:42@gitter_webewizard:matrix.orgWebeWizard (Gitter) ended up submitting a PR that auto generates ops like all the other types diesel-rs/diesel#2278 .
09:14:16@gitter_farkal:matrix.orgEtienne (Gitter) joined the room.
09:14:31@gitter_farkal:matrix.orgEtienne (Gitter) Hey guys what do you think about using sqlx inside diesel ? https://github.com/launchbadge/sqlx
09:14:48@gitter_weiznich:matrix.orgGeorg Semmler (Gitter)Can you explain what you expect from doing that?
09:25:49@gitter_farkal:matrix.orgEtienne (Gitter)The async part and the type safe sql
09:26:32@gitter_farkal:matrix.orgEtienne (Gitter) But i don't know the internal structure of diesel, perhaps it's a stupid suggestion
09:27:22@gitter_weiznich:matrix.orgGeorg Semmler (Gitter)We have already type safe sql. (I would say even more type safe then that what sqlx can offer). For async: I do not see that they solve our main blocker for writing a async interface: Having a sane transaction api, that does not require someone to call explicitly commit or abort.
09:46:45@gitter_farkal:matrix.orgEtienne (Gitter)Ok thanks for the explanations !
09:47:18@gitter_farkal:matrix.orgEtienne (Gitter)I have another question, is there a way to handle concurent insertions with diesel ?
09:47:39@gitter_weiznich:matrix.orgGeorg Semmler (Gitter) Concurrent in which way?
09:47:58@gitter_farkal:matrix.orgEtienne (Gitter)In kube i distribute my software and all of them can insert and read data in the same postgres database
09:48:45@gitter_weiznich:matrix.orgGeorg Semmler (Gitter) Yes, that's fine. Open a connection to the postgres database and run whatever sql statement you want. Postgres can handle that.
09:49:18@gitter_farkal:matrix.orgEtienne (Gitter)But what will append if two instances are asked to create the same object ?
09:49:26@gitter_farkal:matrix.orgEtienne (Gitter)Diesel will send me an error ?
09:49:53@gitter_weiznich:matrix.orgGeorg Semmler (Gitter)Postgres will generate that error, diesel will only give you the error message postgres has generated.
09:50:45@gitter_weiznich:matrix.orgGeorg Semmler (Gitter) (Assumed that the "same object" is somehow forbidden by some unique constrain at database level.)
09:51:21@gitter_farkal:matrix.orgEtienne (Gitter)(yes good assumption)
09:51:45@gitter_farkal:matrix.orgEtienne (Gitter)Ok so i have just to do the good error handling if diesel send me an already exist error
09:52:01@gitter_weiznich:matrix.orgGeorg Semmler (Gitter)Yes
09:53:10@gitter_farkal:matrix.orgEtienne (Gitter)Thank you very much !
09:53:14@gitter_weiznich:matrix.orgGeorg Semmler (Gitter) There is a separate error variant for this case: http://docs.diesel.rs/diesel/result/enum.DatabaseErrorKind.html#variant.UniqueViolation, so just match on the error and see if it's this variant.
09:55:51@gitter_farkal:matrix.orgEtienne (Gitter)Perfect !
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