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extern crate postgres;
extern crate rand;
#[macro_use]
#[cfg(test)]
extern crate lazy_static;
use std::{fmt, mem};
use std::iter::IntoIterator;
use postgres::Connection;
use postgres::types::ToSql;
use postgres::rows::{Rows};
use rand::{thread_rng, Rng};
struct Hex<'a>(&'a [u8]);
impl<'a> fmt::Display for Hex<'a> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
for byte in self.0 {
write!(f, "{:02x}", byte)?;
}
Ok(())
}
}
pub struct Cursor<'conn> {
conn: &'conn Connection,
closed: bool,
cursor_name: String,
fetch_query: String,
batch_size: u32
}
impl<'conn> Cursor<'conn> {
fn new<'c, 'a, D>(builder: Builder<'c, 'a, D>) -> postgres::Result<Cursor<'c>>
where D: fmt::Display + ?Sized
{
let mut bytes: [u8; 8] = unsafe { mem::uninitialized() };
thread_rng().fill_bytes(&mut bytes[..]);
let cursor_name = format!("cursor:{}:{}", builder.tag, Hex(&bytes));
let query = format!("DECLARE \"{}\" CURSOR FOR {}", cursor_name, builder.query);
let fetch_query = format!("FETCH {} FROM \"{}\"", builder.batch_size, cursor_name);
builder.conn.execute("BEGIN", &[])?;
builder.conn.execute(&query[..], builder.params)?;
Ok(Cursor {
closed: false,
conn: builder.conn,
cursor_name,
fetch_query,
batch_size: builder.batch_size,
})
}
pub fn build<'b>(conn: &'b Connection) -> Builder<'b, 'static, str> {
Builder::<str>::new(conn)
}
}
pub struct Iter<'b, 'a: 'b> {
cursor: &'b mut Cursor<'a>,
}
impl<'b, 'a: 'b> Iterator for Iter<'b, 'a> {
type Item = postgres::Result<Rows>;
fn next(&mut self) -> Option<postgres::Result<Rows>> {
if self.cursor.closed {
None
} else {
Some(self.cursor.next_batch())
}
}
}
impl<'a, 'conn> IntoIterator for &'a mut Cursor<'conn> {
type Item = postgres::Result<Rows>;
type IntoIter = Iter<'a, 'conn>;
fn into_iter(self) -> Iter<'a, 'conn> {
self.iter()
}
}
impl<'a> Cursor<'a> {
pub fn iter<'b>(&'b mut self) -> Iter<'b, 'a> {
Iter {
cursor: self,
}
}
fn next_batch(&mut self) -> postgres::Result<Rows> {
let rows = self.conn.query(&self.fetch_query[..], &[])?;
if rows.len() < (self.batch_size as usize) {
self.close()?;
}
Ok(rows)
}
fn close(&mut self) -> postgres::Result<()> {
if !self.closed {
let close_query = format!("CLOSE \"{}\"", self.cursor_name);
self.conn.execute(&close_query[..], &[])?;
self.conn.execute("COMMIT", &[])?;
self.closed = true;
}
Ok(())
}
}
impl<'a> Drop for Cursor<'a> {
fn drop(&mut self) {
let _ = self.close();
}
}
pub struct Builder<'conn, 'builder, D: ?Sized + 'builder> {
batch_size: u32,
query: &'builder str,
conn: &'conn Connection,
tag: &'builder D,
params: &'builder [&'builder ToSql],
}
impl<'conn, 'builder, D: fmt::Display + ?Sized + 'builder> Builder<'conn, 'builder, D> {
fn new<'c>(conn: &'c Connection) -> Builder<'c, 'static, str> {
Builder {
conn,
batch_size: 5_000,
query: "SELECT 1 as one",
tag: "default",
params: &[],
}
}
pub fn query_params(mut self, params: &'builder [&'builder ToSql]) -> Self {
self.params = params;
self
}
pub fn batch_size(mut self, batch_size: u32) -> Self {
self.batch_size = batch_size;
self
}
pub fn tag<D2: fmt::Display + ?Sized>(self, tag: &'builder D2) -> Builder<'conn, 'builder, D2> {
Builder {
batch_size: self.batch_size,
query: self.query,
conn: self.conn,
tag: tag,
params: self.params
}
}
pub fn query(mut self, query: &'builder str) -> Self {
self.query = query;
self
}
pub fn finalize(self) -> postgres::Result<Cursor<'conn>> {
Cursor::new(self)
}
}
#[cfg(test)]
mod tests {
use std::sync::Mutex;
use postgres::{Connection, TlsMode};
use super::Cursor;
lazy_static! {
static ref LOCK: Mutex<u8> = {
Mutex::new(0)
};
}
fn synchronized<F: FnOnce() -> T, T>(func: F) -> T {
let _guard = LOCK.lock().unwrap_or_else(|e| e.into_inner());
func()
}
fn with_items<F: FnOnce(&Connection) -> T, T>(items: i32, func: F) -> T {
synchronized(|| {
let conn = get_connection();
conn.execute("TRUNCATE TABLE products", &[]).expect("truncate");
for i in 0..items {
conn.execute("INSERT INTO products (id) VALUES ($1)", &[&i]).expect("insert");
}
func(&conn)
})
}
fn get_connection() -> Connection {
Connection::connect("postgres://jwilm@127.0.0.1/postgresql_cursor_test", TlsMode::None)
.expect("connect")
}
#[test]
fn test_framework_works() {
let count = 183;
with_items(count, |conn| {
for row in &conn.query("SELECT COUNT(*) FROM products", &[]).unwrap() {
let got: i64 = row.get(0);
assert_eq!(got, count as i64);
}
});
}
#[test]
fn cursor_iter_works_when_batch_size_divisible() {
with_items(200, |conn| {
let mut cursor = Cursor::build(conn)
.batch_size(10)
.query("SELECT id FROM products")
.finalize().unwrap();
let mut got = 0;
for batch in &mut cursor {
let batch = batch.unwrap();
got += batch.len();
}
assert_eq!(got, 200);
});
}
#[test]
fn cursor_iter_works_when_batch_size_remainder() {
with_items(197, |conn| {
let mut cursor = Cursor::build(conn)
.batch_size(10)
.query("SELECT id FROM products")
.finalize().unwrap();
let mut got = 0;
for batch in &mut cursor {
let batch = batch.unwrap();
got += batch.len();
}
assert_eq!(got, 197);
});
}
#[test]
fn build_cursor_with_tag() {
with_items(1, |conn| {
{
let cursor = Cursor::build(conn)
.tag("foobar")
.finalize().unwrap();
assert!(cursor.cursor_name.starts_with("cursor:foobar"));
}
struct Foo;
use std::fmt;
impl fmt::Display for Foo {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "foo-{}", 1)
}
}
{
let foo = Foo;
let cursor = Cursor::build(conn)
.tag(&foo)
.finalize().unwrap();
println!("{}", cursor.cursor_name);
assert!(cursor.cursor_name.starts_with("cursor:foo-1"));
}
});
}
#[test]
fn cursor_with_long_tag() {
with_items(100, |conn| {
let mut cursor = Cursor::build(conn)
.tag("really-long-tag-damn-that-was-only-three-words-foo-bar-baz")
.query("SELECT id FROM products")
.finalize().unwrap();
let mut got = 0;
for batch in &mut cursor {
let batch = batch.unwrap();
got += batch.len();
}
assert_eq!(got, 100);
});
}
#[test]
fn cursor_with_params() {
with_items(100, |conn| {
let mut cursor = Cursor::build(conn)
.query("SELECT id FROM products WHERE id > $1 AND id < $2")
.query_params(&[&1, &10])
.finalize().unwrap();
let mut got = 0;
for batch in &mut cursor {
let batch = batch.unwrap();
got += batch.len();
}
assert_eq!(got, 8);
});
}
}