Rust diesel 有条件地过滤查询

Question

我正尝试在一个项目中使用柴油，我想要一个“可过滤”的类型。这个想法是你可以去 /api/foo?id=10&bar=11 它会 return 一个结构 Foo:

struct Foo {
    id: Option<i64>,
    bar: Option<i64>,
    name: Option<String>,
}

如：

Foo {
   id: Some(10),
   bar: Some(11),
   name: None,
}

我一直在互联网上搜索一种方法来过滤现有的字段，但我无法找到有效的解决方案。我最初使用 mysql driver 并使用 proc 宏构建 sql 查询，但使用柴油要好得多，我想知道是否有办法获得与 mysql driver 柴油。

Answer 1

您可以使用into_boxed方法，即：

Boxes the pieces of a query into a single type. This is useful for cases where you want to conditionally modify a query, but need the type to remain the same. A boxed query will incur a minor performance penalty, as the query builder can no longer be inlined by the compiler. For most applications this cost will be minimal.

use crate::schema::foo;

let mut query = foo::table.into_boxed();

if let Some(id) = foo.id {
    query = query.filter(foo::id.eq(id));
}

if let Some(bar) = foo.bar {
    query = query.filter(foo::bar.eq(bar));
}

if let Some(name) = foo.name {
    query = query.filter(foo::name.eq(name));
}

let results = query
    .load::<Foo>(&conn)
    .expect("error loading foo");

Rust diesel 有条件地过滤查询

Rust diesel conditionally filter a query

backend

rust

rust-diesel