Problem:something wrong with official guide.

[ghost]

Versions

• Rust: Nightly
• Diesel: 1.0.0
• Database: MySQL5.7
• Operating System OSX

Problem Description

Follow Official Guide,When I Finished **show_posts.rs**,and I execute **cargo run --bin show_posts**,a error occurs.

--> src/bin/show_posts.rs:14:10
|
14 | .load::(&connection)
| ^^^^ the trait diesel::deserialize::FromSql<diesel::sql_types::BigInt, diesel::mysql::Mysql> is not implemented for i32
|

What does this mean?
How can I solve it?

Thanks very much.

[brandur]

diesel::sql_types::BigInt is representative of the BIGINT SQL type. You can see from the MySQL documentation on integer types here that BIGINT is an 8-byte integer. That's inherently incompatible with an i32 which is 32 bits (or 4 bytes), and Diesel is smart enough to understand that there's a potentially unsafe condition when you try to load a BIGINT that's too large into an i32, and won't let your program compile.

Solution: try i64 (64 bits, or 8 bytes) instead.

(Disclaimer: I'm not a maintainer of this project, but hopefully this is helpful.)

[sgrif]

Above comment is correct. Either use i64 on the Rust side, or change the type to INTEGER on the SQL side.

[ghost]

Thanks,