[英]How to insert HashMap into PostgreSQL as JSON type?
contacts
has a data structure as HashMap
, I'm using PostgreSQL
client - rust-postgres to insert contact
's key and value into a table, then I want to select from the table. contacts
的数据结构为HashMap
,我使用PostgreSQL
客户端 - rust-postgres将contact
的键和值插入表中,然后我想从表中进行选择。 Below is what I tried so far.以下是我到目前为止所尝试的。 I need help with writing the right syntax.
我需要帮助编写正确的语法。
use postgres::{Client, NoTls};
use std::collections::HashMap;
fn main() -> Result<(), Box<dyn std::error::Error>> {
let mut client = Client::connect("host=127.0.0.1 user=postgres", NoTls)?;
client.simple_query("
DROP TABLE
IF EXISTS following_relation;
")?;
client.simple_query("
CREATE TABLE following_relation (
id SERIAL NOT NULL PRIMARY KEY,
relation JSON NOT NULL
)
")?;
let mut contacts = HashMap::new();
let mut v: Vec<String> = Vec::new();
v = vec!["jump".to_owned(), "jog".to_string()];
contacts.insert("Ashley", v.clone());
for (name, hobby) in contacts.iter() {
// 1. How to write sql statement with parameters?
client.execute(
"INSERT INTO following_relation(relation)
VALUE ('{"name" : $1, "hobby" : $2}')",
&[&name, &hobby],
)?;
}
for row in client.query("SELECT id, relation FROM following_relation", &[])? {
// 2. How to read from parse the result?
let id: i32 = row.get(0);
let relation = row.get(1);
//println!("found person: {} {} {:?}", id, relation["name"], relation["hobby"]);
}
Ok(())
}
I've been given the hints我得到了提示
- Like the error message says, your query has VALUE but it needs to be VALUES.
就像错误消息所说的那样,您的查询具有 VALUE,但必须是 VALUES。
- Query parameters cannot be interpolated into strings.
查询参数不能插入到字符串中。 You should build the object in Rust, and usehttps://docs.rs/postgres/0.17.0/postgres/types/struct.Json.html to wrap the types when inserting.
您应该在 Rust 中构建对象,并在插入时使用https://docs.rs/postgres/0.17.0/postgres/types/struct.Json.html来包装类型。
I have no idea how to apply pub struct Json<T>(pub T);
我不知道如何应用
pub struct Json<T>(pub T);
here.这里。
How to build the query
required in function execute
?如何构建函数
execute
所需的query
?
pub fn execute<T: ?Sized>(
&mut self,
query: &T,
params: &[&(dyn ToSql + Sync)]
) -> Result<u64, Error>
where
T: ToStatement,
UPDATED, I tried with a more brief code sample更新,我尝试使用更简短的代码示例
use postgres::{Client, NoTls};
use postgres::types::Json;
use serde::{Deserialize, Serialize};
#[derive(Debug, Serialize, Deserialize)]
struct relations {
name : String,
hobby: Vec<String>
}
pub struct Json<T>(pub T);
fn main() -> Result<(), Box<dyn std::error::Error>> {
let mut client = Client::connect("host=127.0.0.1 user=postgres", NoTls)?;
client.simple_query("
DROP TABLE
IF EXISTS following_relation;
")?;
client.simple_query("
CREATE TABLE following_relation (
id SERIAL PRIMARY KEY,
relation JSON NOT NULL
)
")?;
let rel = relations {
name: "czfzdxx".to_string(),
hobby: vec![
"basketball".to_string(),
"jogging".to_string()
],
};
client.execute(
r#"INSERT INTO following_relation(relation)
VALUE ($1)"#,
&[&Json(&rel)]
)?;
Ok(())
}
I get我得到
error[E0432]: unresolved import `postgres::types::Json`
You want Rust raw string literal :你想要 Rust 原始字符串文字:
for (name, hobby) in contacts.iter() {
client.execute(
r#"INSERT INTO following_relation(relation)
VALUE ('{"name" : ($1), "hobby" : ($2)}')"#,
&[&name, &following],
)?;
}
Between the start r#"
and the end "#
, your string literals can have any character except #
itself without escaping.在开始
r#"
和结束"#
,您的字符串文字可以包含除#
本身之外的任何字符而无需转义。 If you also want #
itself, then starts the raw string literals with multiple #
s and ends with matching number of #
s.如果您还想要
#
本身,则以多个#
开始原始字符串文字,并以匹配数量的#
结束。
Here is main.rs
:这是
main.rs
:
use postgres::{Client, NoTls};
use serde::{Deserialize, Serialize};
use postgres_types::Json;
use postgres_types::{FromSql};
#[derive(Debug, Deserialize, Serialize, FromSql)]
struct Relation {
name : String,
hobby: Vec<String>
}
fn main() -> Result<(), Box<dyn std::error::Error>> {
let mut client = Client::connect("host=127.0.0.1 user=postgres", NoTls)?;
client.simple_query("
DROP TABLE
IF EXISTS following_relation;
")?;
client.simple_query("
CREATE TABLE following_relation (
id SERIAL PRIMARY KEY,
relation JSON NOT NULL
)
")?;
let rel = Relation {
name: "czfzdxx".to_string(),
hobby: vec![
"basketball".to_string(),
"jogging".to_string()
],
};
client.execute(
"INSERT INTO following_relation (relation) VALUES ($1)",
&[&Json::<Relation>(rel)]
)?;
for row in &client.query("SELECT relation FROM following_relation", &[]).unwrap() {
let rel: Json<Relation> = row.get(0);
println!("{:?}", rel);
}
Ok(())
}
and Cargo.toml
:和
Cargo.toml
:
[package]
name = "testapp"
version = "0.1.0"
edition = "2018"
# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
[dependencies]
postgres = {version = "0.17.0"}
tokio-postgres = "0.5.1"
serde = {version = "1.0.104", features = ["derive"]}
postgres-types = {version = "0.1.0", features = ["derive", "with-serde_json-1"]}
serde_json = "1.0.45"
And here is the relevant documentation used: postgres_types and postgres .这是使用的相关文档: postgres_types和postgres 。 Search for
serde_json
, ToSql
and FromSql
traits are implemented for this third-party type.搜索
serde_json
、 ToSql
和FromSql
特征是为此第三方类型实现的。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.