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use log::trace;
use mysql::Params;
use mysql::Params::Positional;
use mysql::Pool;
use smallvec::smallvec;
use crate::error::Error;
use crate::error::Result;
use crate::writer::Trade;
use crate::writer::Writer;
pub trait MySQLWriterElement {
fn to_params(&self) -> Params;
fn table_def() -> Vec<TableDef>;
fn index_names() -> Vec<String>;
fn create_table_stmt(table_name: &str) -> String {
let columns = Self::table_def()
.iter()
.map(|TableDef(k, v)| format!("{} {}", k, v))
.collect::<Vec<String>>();
let index = Self::index_names()
.iter()
.map(|name| format!("KEY `ind_{s}` (`{s}`)", s = name))
.collect::<Vec<String>>();
let definition = [&columns[..], &index[..]].concat().join(", ");
format!(
r"CREATE TABLE IF NOT EXISTS {} ( {} );",
table_name, definition
)
}
}
#[derive(Debug)]
pub struct TableDef(String, String);
impl TableDef {
pub fn new(s1: &str, s2: &str) -> Self {
TableDef(String::from(s1), String::from(s2))
}
}
#[derive(Debug)]
pub struct MySQLWriter<'a> {
table_name: &'a str,
connection: Pool,
}
impl<'a> MySQLWriter<'a> {
pub fn new(table_name: &'a str, database_url: &str) -> Self {
trace!("connect to {}", database_url);
let connection = Pool::new(database_url).expect("cannot connect to DB");
MySQLWriter {
table_name,
connection,
}
}
fn create_table<T: MySQLWriterElement>(&self) {
let create_stmt = T::create_table_stmt(self.table_name);
self.connection.prep_exec(create_stmt, ()).unwrap();
}
fn bulk_insert<T: MySQLWriterElement>(&self, v: &[T]) -> Result<u64> {
const MAX_PARAM_NUM: usize = 10000;
let col_names = T::table_def()
.iter()
.map(|TableDef(k, _)| k.clone())
.collect::<Vec<String>>();
v.chunks(MAX_PARAM_NUM)
.map(|x| {
let placeholder = format!(
"({})",
col_names
.iter()
.map(|_| "?")
.collect::<Vec<&str>>()
.join(",")
);
let stmt = format!(
r#"REPLACE INTO {} ({}) VALUES {} ;"#,
self.table_name,
col_names.join(","),
vec![placeholder; x.len()].join(",")
);
let params: Result<Params> = x
.iter()
.map(|e| e.to_params())
.map(|p: Params| {
p.into_positional(&col_names)
.map_err(|e| Error::MySqlMissingNamedParameter(Box::new(e)))
})
.collect::<Result<Vec<Params>>>()
.map(|vp| {
let u = vp
.into_iter()
.flat_map(|v| if let Positional(ps) = v { ps } else { smallvec![] })
.collect();
Positional(u)
});
params.and_then(|p: Params| {
self.connection
.prep_exec(stmt, p)
.map(|result| result.affected_rows())
.map_err(Error::from)
})
})
.collect::<Result<Vec<u64>>>()
.and_then(|e| Ok(e.iter().sum()))
}
}
impl<'a> Writer for MySQLWriter<'a> {
fn write(&mut self, trades: &[Trade]) -> Result<u64> {
self.create_table::<Trade>();
self.bulk_insert(trades)
}
}