homework-jianmu/examples/rust/examples/query.rs

107 lines
3.1 KiB
Rust

use std::time::Duration;
use chrono::{DateTime, Local};
use taos::*;
#[tokio::main]
async fn main() -> anyhow::Result<()> {
let dsn = "taos://";
let opts = PoolBuilder::new()
.max_size(5000) // max connections
.max_lifetime(Some(Duration::from_secs(60 * 60))) // lifetime of each connection
.min_idle(Some(1000)) // minimal idle connections
.connection_timeout(Duration::from_secs(2));
let pool = TaosBuilder::from_dsn(dsn)?.with_pool_builder(opts)?;
let taos = pool.get()?;
let db = "query";
// prepare database
taos.exec_many([
format!("DROP DATABASE IF EXISTS `{db}`"),
format!("CREATE DATABASE `{db}`"),
format!("USE `{db}`"),
])
.await?;
let inserted = taos.exec_many([
// create super table
"CREATE TABLE `meters` (`ts` TIMESTAMP, `current` FLOAT, `voltage` INT, `phase` FLOAT) TAGS (`groupid` INT, `location` BINARY(16))",
// create child table
"CREATE TABLE `d0` USING `meters` TAGS(0, 'Los Angles')",
// insert into child table
"INSERT INTO `d0` values(now - 10s, 10, 116, 0.32)",
// insert with NULL values
"INSERT INTO `d0` values(now - 8s, NULL, NULL, NULL)",
// insert and automatically create table with tags if not exists
"INSERT INTO `d1` USING `meters` TAGS(1, 'San Francisco') values(now - 9s, 10.1, 119, 0.33)",
// insert many records in a single sql
"INSERT INTO `d1` values (now-8s, 10, 120, 0.33) (now - 6s, 10, 119, 0.34) (now - 4s, 11.2, 118, 0.322)",
]).await?;
assert_eq!(inserted, 6);
loop {
let count: usize = taos
.query_one("select count(*) from `meters`")
.await?
.unwrap_or_default();
if count >= 6 {
break;
} else {
println!("waiting for data");
}
}
let mut result = taos.query("select tbname, * from `meters`").await?;
for field in result.fields() {
println!("got field: {}", field.name());
}
// Query option 1, use rows stream.
let mut rows = result.rows();
let mut nrows = 0;
while let Some(row) = rows.try_next().await? {
for (col, (name, value)) in row.enumerate() {
println!(
"[{}] got value in col {} (named `{:>8}`): {}",
nrows, col, name, value
);
}
nrows += 1;
}
// Query options 2, use deserialization with serde.
#[derive(Debug, serde::Deserialize)]
#[allow(dead_code)]
struct Record {
tbname: String,
// deserialize timestamp to chrono::DateTime<Local>
ts: DateTime<Local>,
// float to f32
current: Option<f32>,
// int to i32
voltage: Option<i32>,
phase: Option<f32>,
groupid: i32,
// binary/varchar to String
location: String,
}
let records: Vec<Record> = taos
.query("select tbname, * from `meters`")
.await?
.deserialize()
.try_collect()
.await?;
dbg!(result.summary());
assert_eq!(records.len(), 6);
dbg!(records);
Ok(())
}