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use boolinator::Boolinator; use futures::stream::{self, once, StreamExt, TryStream, TryStreamExt}; use serde::Serialize; use std::fmt::Debug; use std::pin::Pin; use std::rc::Rc; use thiserror::Error as ThisError; use sqlparser::ast::{Ident, Join as AstJoin, JoinConstraint, JoinOperator}; use super::context::{BlendContext, FilterContext}; use super::filter::Filter; use crate::data::Table; use crate::result::{Error, Result}; use crate::store::Store; use crate::utils::OrStream; #[derive(ThisError, Serialize, Debug, PartialEq)] pub enum JoinError { #[error("unimplemented! join not supported")] JoinTypeNotSupported, #[error("unimplemented! using on join not supported")] UsingOnJoinNotSupported, #[error("unimplemented! natural on join not supported")] NaturalOnJoinNotSupported, #[error("umimplemented! failed to get table name")] FailedToGetTableName, } pub struct Join<'a, T: 'static + Debug> { storage: &'a dyn Store<T>, join_clauses: &'a [AstJoin], filter_context: Option<Rc<FilterContext<'a>>>, } type JoinItem<'a> = Rc<BlendContext<'a>>; type Joined<'a> = Pin<Box<dyn TryStream<Ok = JoinItem<'a>, Error = Error, Item = Result<JoinItem<'a>>> + 'a>>; impl<'a, T: 'static + Debug> Join<'a, T> { pub fn new( storage: &'a dyn Store<T>, join_clauses: &'a [AstJoin], filter_context: Option<Rc<FilterContext<'a>>>, ) -> Self { Self { storage, join_clauses, filter_context, } } pub async fn apply( &self, init_context: Result<BlendContext<'a>>, join_columns: Rc<Vec<Rc<Vec<Ident>>>>, ) -> Result<Joined<'a>> { let init_context = init_context.map(Rc::new); let init_rows: Joined<'a> = Box::pin(stream::once(async { init_context })); let filter_context = self.filter_context.as_ref().map(Rc::clone); let joins = self .join_clauses .iter() .enumerate() .map(move |(i, join_clause)| { let join_columns = Rc::clone(&join_columns[i]); Ok::<_, Error>((join_clause, join_columns)) }); let rows = stream::iter(joins) .try_fold(init_rows, |rows, (join_clause, join_columns)| { let storage = self.storage; let filter_context = filter_context.as_ref().map(Rc::clone); async move { let rows = rows .map(Ok) .and_then(move |blend_context| { let columns = Rc::clone(&join_columns); let filter_context = filter_context.as_ref().map(Rc::clone); join(storage, filter_context, join_clause, columns, blend_context) }) .try_flatten(); Ok::<Joined<'a>, _>(Box::pin(rows)) } }) .await?; Ok(Box::pin(rows)) } } async fn join<'a, T: 'static + Debug>( storage: &'a dyn Store<T>, filter_context: Option<Rc<FilterContext<'a>>>, ast_join: &'a AstJoin, columns: Rc<Vec<Ident>>, blend_context: Result<Rc<BlendContext<'a>>>, ) -> Result<Joined<'a>> { let AstJoin { relation, join_operator, } = ast_join; let table = Table::new(relation)?; let table_name = table.get_name(); let table_alias = table.get_alias(); let blend_context = blend_context?; let init_context = Rc::new(BlendContext::new( table.get_alias(), Rc::clone(&columns), None, Some(Rc::clone(&blend_context)), )); let fetch_joined = |constraint: &'a JoinConstraint| { fetch_joined( storage, table_name, table_alias, Rc::clone(&columns), filter_context, blend_context, constraint, ) }; match join_operator { JoinOperator::Inner(constraint) => fetch_joined(constraint).await.map(|rows| { let rows: Joined<'a> = Box::pin(rows); rows }), JoinOperator::LeftOuter(constraint) => fetch_joined(constraint).await.map(|rows| { let init_rows = once(async { Ok(init_context) }); let rows: Joined<'a> = Box::pin(OrStream::new(rows, init_rows)); rows }), _ => Err(JoinError::JoinTypeNotSupported.into()), } } async fn fetch_joined<'a, T: 'static + Debug>( storage: &'a dyn Store<T>, table_name: &'a str, table_alias: &'a str, columns: Rc<Vec<Ident>>, filter_context: Option<Rc<FilterContext<'a>>>, blend_context: Rc<BlendContext<'a>>, constraint: &'a JoinConstraint, ) -> Result<impl TryStream<Ok = JoinItem<'a>, Error = Error, Item = Result<JoinItem<'a>>> + 'a> { let where_clause = match constraint { JoinConstraint::On(where_clause) => Some(where_clause), JoinConstraint::Using(_) => { return Err(JoinError::UsingOnJoinNotSupported.into()); } JoinConstraint::Natural => { return Err(JoinError::NaturalOnJoinNotSupported.into()); } }; let rows = storage .scan_data(table_name) .await .map(stream::iter)? .try_filter_map(move |(_, row)| { let filter_context = FilterContext::concat( filter_context.as_ref().map(Rc::clone), Some(&blend_context).map(Rc::clone), ); let filter_context = Some(filter_context).map(Rc::new); let blend_context = Rc::clone(&blend_context); let columns = Rc::clone(&columns); async move { let filter = Filter::new(storage, where_clause, filter_context, None); let context = Rc::new(BlendContext::new( table_alias, Rc::clone(&columns), Some(row), Some(&blend_context).map(Rc::clone), )); filter .check(Rc::clone(&context)) .await .map(|pass| pass.as_some(context)) } }); Ok(rows) }