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use async_recursion::async_recursion; use boolinator::Boolinator; use futures::stream::{self, StreamExt, TryStreamExt}; use im_rc::HashMap; use serde::Serialize; use std::fmt::Debug; use std::rc::Rc; use thiserror::Error; use sqlparser::ast::{BinaryOperator, Expr, Function, UnaryOperator}; use super::context::{BlendContext, FilterContext}; use super::evaluate::{evaluate, Evaluated}; use super::select::select; use crate::data::Value; use crate::result::Result; use crate::store::Store; #[derive(Error, Serialize, Debug, PartialEq)] pub enum FilterError { #[error("unimplemented")] Unimplemented, } pub struct Filter<'a, T: 'static + Debug> { storage: &'a dyn Store<T>, where_clause: Option<&'a Expr>, context: Option<Rc<FilterContext<'a>>>, aggregated: Option<Rc<HashMap<&'a Function, Value>>>, } impl<'a, T: 'static + Debug> Filter<'a, T> { pub fn new( storage: &'a dyn Store<T>, where_clause: Option<&'a Expr>, context: Option<Rc<FilterContext<'a>>>, aggregated: Option<Rc<HashMap<&'a Function, Value>>>, ) -> Self { Self { storage, where_clause, context, aggregated, } } pub async fn check(&self, blend_context: Rc<BlendContext<'a>>) -> Result<bool> { match self.where_clause { Some(expr) => { let context = self.context.as_ref().map(Rc::clone); let context = FilterContext::concat(context, Some(blend_context)); let context = Some(context).map(Rc::new); let aggregated = self.aggregated.as_ref().map(Rc::clone); check_expr(self.storage, context, aggregated, expr).await } None => Ok(true), } } } #[async_recursion(?Send)] pub async fn check_expr<T: 'static + Debug>( storage: &dyn Store<T>, filter_context: Option<Rc<FilterContext<'async_recursion>>>, aggregated: Option<Rc<HashMap<&'async_recursion Function, Value>>>, expr: &Expr, ) -> Result<bool> { let evaluate = |expr: &'async_recursion Expr| { let filter_context = filter_context.as_ref().map(Rc::clone); let aggregated = aggregated.as_ref().map(Rc::clone); evaluate(storage, filter_context, aggregated, expr, false) }; let check = |expr| { let filter_context = filter_context.as_ref().map(Rc::clone); let aggregated = aggregated.as_ref().map(Rc::clone); check_expr(storage, filter_context, aggregated, expr) }; match expr { Expr::BinaryOp { op, left, right } => { let zip_evaluate = || async move { let l = evaluate(left).await?; let r = evaluate(right).await?; Ok((l, r)) }; let zip_check = || async move { let l = check(left).await?; let r = check(right).await?; Ok((l, r)) }; match op { BinaryOperator::Eq => zip_evaluate().await.map(|(l, r)| l == r), BinaryOperator::NotEq => zip_evaluate().await.map(|(l, r)| l != r), BinaryOperator::And => zip_check().await.map(|(l, r)| l && r), BinaryOperator::Or => zip_check().await.map(|(l, r)| l || r), BinaryOperator::Lt => zip_evaluate().await.map(|(l, r)| l < r), BinaryOperator::LtEq => zip_evaluate().await.map(|(l, r)| l <= r), BinaryOperator::Gt => zip_evaluate().await.map(|(l, r)| l > r), BinaryOperator::GtEq => zip_evaluate().await.map(|(l, r)| l >= r), _ => Err(FilterError::Unimplemented.into()), } } Expr::UnaryOp { op, expr } => match op { UnaryOperator::Not => check(&expr).await.map(|v| !v), _ => Err(FilterError::Unimplemented.into()), }, Expr::Nested(expr) => check(&expr).await, Expr::InList { expr, list, negated, } => { let negated = *negated; let target = evaluate(expr).await?; stream::iter(list.iter()) .filter_map(|expr| { let target = ⌖ async move { evaluate(expr).await.map_or_else( |error| Some(Err(error)), |evaluated| (target == &evaluated).as_some(Ok(!negated)), ) } }) .take(1) .collect::<Vec<_>>() .await .into_iter() .next() .unwrap_or(Ok(negated)) } Expr::InSubquery { expr, subquery, negated, } => { let target = evaluate(expr).await?; select(storage, &subquery, filter_context) .await? .try_filter_map(|row| { let target = ⌖ async move { let value = row.take_first_value()?; (target == &Evaluated::ValueRef(&value)) .as_some(Ok(!negated)) .transpose() } }) .take(1) .collect::<Vec<_>>() .await .into_iter() .next() .unwrap_or(Ok(*negated)) } Expr::Between { expr, negated, low, high, } => { let negated = *negated; let target = evaluate(expr).await?; Ok(negated ^ (evaluate(low).await? <= target && target <= evaluate(high).await?)) } Expr::Exists(query) => Ok(select(storage, query, filter_context) .await? .into_stream() .take(1) .try_collect::<Vec<_>>() .await? .get(0) .is_some()), Expr::IsNull(expr) => Ok(!evaluate(expr).await?.is_some()), Expr::IsNotNull(expr) => Ok(evaluate(expr).await?.is_some()), _ => Err(FilterError::Unimplemented.into()), } }