如何应要求将后Gresql数字类型解析为生锈的数字类型？
相关代码是这样：
use chrono::{DateTime, Utc}; // 0.4.10
use postgres::{Client, NoTls, Config, types::{FromSql, Type}};
//...
for row in client.query("SELECT * FROM pricetable;", &[])? {
let time:DateTime<Utc> = row.get(0);
let price:i64 = row.get(1);
println!("found datum: {:?}", &row);
println!("found datum: {} {} ", time, price);
}
运行时我遇到的错误是：
thread 'main' panicked at 'error retrieving column 1: error
deserializing column 1: cannot convert between the Rust type `i64`
and the Postgres type `numeric`', /home/me/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-postgres-0.7.6/src/row.rs:151:25
其中Price是numeric在SQL类型方面键入。我似乎无法将其解析为任何标准的生锈类型，例如u64，i64等。鉴于它们似乎无法实现fromsql 特征 ）postgres 板条板出口。 （我意识到这清楚地表明在这里，但这不是我的错误。 0_4“]}
我已经看到人们建议声明自己的包装器类型，例如struct float64（u64） 和实现 tosql和 fromsql 上面。是否有参考实现？
Relevant code is this:
use chrono::{DateTime, Utc}; // 0.4.10
use postgres::{Client, NoTls, Config, types::{FromSql, Type}};
//...
for row in client.query("SELECT * FROM pricetable;", &[])? {
let time:DateTime<Utc> = row.get(0);
let price:i64 = row.get(1);
println!("found datum: {:?}", &row);
println!("found datum: {} {} ", time, price);
}
The error I'm getting when I run this is thus:
thread 'main' panicked at 'error retrieving column 1: error
deserializing column 1: cannot convert between the Rust type `i64`
and the Postgres type `numeric`', /home/me/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-postgres-0.7.6/src/row.rs:151:25
where price is a NUMERIC type in terms of SQL types. I can't seem to parse it into any of the standard rust types like u64,i64 etc. given that they don't seem to implement FromSql trait that the postgres crate exports. (I realize it's stated plainly here that they it is, but that's not what my error says. Do i need to enable some feature? Cargo.toml has postgres={version="0.19.3",features= ["with-chrono-0_4"]})
I've seen people recommend declaring your own wrapper type like struct Float64(u64) and implementing ToSql and FromSql on those.. Is that the only way to get data out of Postgres into Rust? Is there a reference implementation if so?
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使用
DECIMAL代替本机数据类型：它IncementsFromsql和TOSQL实际上未针对常规Rust的数值类型和SQL的数字实现。这是由于数字是任意的精度。Use something like
decimalinstead of the native data types: it impementsFromSqlandToSqlwhich are not in fact implemented for regular rust's numerical types and SQL'sNUMERIC. This is due toNUMERICbeing of arbitrary precision.