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use crate::{
errors::{unexpected, Error, Result},
messages::{BoltRequest, BoltResponse},
pool::ManagedConnection,
row::Row,
txn::TransactionHandle,
types::BoltList,
DeError,
};
use futures::{stream::try_unfold, TryStream};
use serde::de::DeserializeOwned;
use std::collections::VecDeque;
/// An abstraction over a stream of rows, this is returned as a result of [`crate::Txn::execute`].
///
/// A stream needs a running transaction to be consumed.
#[must_use = "Results must be streamed through with `next` in order to execute the query"]
pub struct RowStream {
qid: i64,
fields: BoltList,
state: State,
fetch_size: usize,
buffer: VecDeque<Row>,
}
/// An abstraction over a stream of rows, this is returned as a result of [`crate::Graph::execute`].
///
/// A stream will contain a connection from the connection pool which will be released to the pool
/// when the stream is dropped.
#[must_use = "Results must be streamed through with `next` in order to execute the query"]
pub struct DetachedRowStream {
stream: RowStream,
connection: ManagedConnection,
}
impl RowStream {
pub(crate) fn new(qid: i64, fields: BoltList, fetch_size: usize) -> Self {
RowStream {
qid,
fields,
fetch_size,
state: State::Ready,
buffer: VecDeque::with_capacity(fetch_size),
}
}
}
impl DetachedRowStream {
pub(crate) fn new(stream: RowStream, connection: ManagedConnection) -> Self {
DetachedRowStream { stream, connection }
}
}
impl RowStream {
/// A call to next() will return a row from an internal buffer if the buffer has any entries,
/// if the buffer is empty and the server has more rows left to consume, then a new batch of rows
/// are fetched from the server (using the fetch_size value configured see [`crate::ConfigBuilder::fetch_size`])
pub async fn next(&mut self, mut handle: impl TransactionHandle) -> Result<Option<Row>> {
loop {
match self.state {
State::Ready => {
let pull = BoltRequest::pull(self.fetch_size, self.qid);
let connection = handle.connection();
connection.send(pull).await?;
self.state = State::Streaming;
}
State::Streaming => {
let connection = handle.connection();
match connection.recv().await {
Ok(BoltResponse::Success(s)) => {
if s.get("has_more").unwrap_or(false) {
self.state = State::Buffered;
} else {
self.state = State::Complete;
}
}
Ok(BoltResponse::Record(record)) => {
let row = Row::new(self.fields.clone(), record.data);
self.buffer.push_back(row);
}
msg => return Err(unexpected(msg, "PULL")),
}
}
State::Buffered => {
if !self.buffer.is_empty() {
return Ok(self.buffer.pop_front());
}
self.state = State::Ready;
}
State::Complete => {
return Ok(self.buffer.pop_front());
}
}
}
}
/// Turns this RowStream into a [`futures::stream::TryStream`] where
/// every element is a [`crate::row::Row`].
pub fn into_stream(
self,
handle: impl TransactionHandle,
) -> impl TryStream<Ok = Row, Error = Error> {
try_unfold((self, handle), |(mut stream, mut hd)| async move {
match stream.next(&mut hd).await {
Ok(Some(row)) => Ok(Some((row, (stream, hd)))),
Ok(None) => Ok(None),
Err(e) => Err(e),
}
})
}
/// Turns this RowStream into a [`futures::stream::TryStream`] where
/// every row is converted into a `T` by calling [`crate::row::Row::to`].
pub fn into_stream_as<T: DeserializeOwned>(
self,
handle: impl TransactionHandle,
) -> impl TryStream<Ok = T, Error = Error> {
self.into_stream_de(handle, |row| row.to::<T>())
}
/// Turns this RowStream into a [`futures::stream::TryStream`] where
/// the value at the given column is converted into a `T`
/// by calling [`crate::row::Row::get`].
pub fn column_into_stream<'db, T: DeserializeOwned + 'db>(
self,
handle: impl TransactionHandle + 'db,
column: &'db str,
) -> impl TryStream<Ok = T, Error = Error> + 'db {
self.into_stream_de(handle, move |row| row.get::<T>(column))
}
fn into_stream_de<T: DeserializeOwned>(
self,
handle: impl TransactionHandle,
deser: impl Fn(Row) -> Result<T, DeError>,
) -> impl TryStream<Ok = T, Error = Error> {
try_unfold(
(self, handle, deser),
|(mut stream, mut hd, de)| async move {
match stream.next(&mut hd).await {
Ok(Some(row)) => match de(row) {
Ok(res) => Ok(Some((res, (stream, hd, de)))),
Err(e) => Err(Error::DeserializationError(e)),
},
Ok(None) => Ok(None),
Err(e) => Err(e),
}
},
)
}
}
impl DetachedRowStream {
/// A call to next() will return a row from an internal buffer if the buffer has any entries,
/// if the buffer is empty and the server has more rows left to consume, then a new batch of rows are fetched from the server (using the
/// fetch_size value configured see [`crate::ConfigBuilder::fetch_size`])
pub async fn next(&mut self) -> Result<Option<Row>> {
self.stream.next(&mut self.connection).await
}
/// Turns this RowStream into a [`futures::stream::TryStream`] where
/// every element is a [`crate::row::Row`].
pub fn into_stream(self) -> impl TryStream<Ok = Row, Error = Error> {
self.stream.into_stream(self.connection)
}
/// Turns this RowStream into a [`futures::stream::TryStream`] where
/// every row is converted into a `T` by calling [`crate::row::Row::to`].
/// If the conversion fails and the result stream has exactly one column,
/// that single value will be converted by calling [`crate::BoltType::to`].
pub fn into_stream_as<T: DeserializeOwned>(self) -> impl TryStream<Ok = T, Error = Error> {
self.stream.into_stream_as(self.connection)
}
/// Turns this RowStream into a [`futures::stream::TryStream`] where
/// the value at the given column is converted into a `T`
/// by calling [`crate::row::Row::get`].
pub fn column_into_stream<'db, T: DeserializeOwned + 'db>(
self,
column: &'db str,
) -> impl TryStream<Ok = T, Error = Error> + 'db {
self.stream.column_into_stream(self.connection, column)
}
}
#[derive(Copy, Clone, PartialEq, Debug)]
enum State {
Ready,
Streaming,
Buffered,
Complete,
}