Feature: Add fallback reason to the explanation (#2647)

lib/src/dbs/explanation.rs

@@ -1,3 +1,4 @@
+use crate::ctx::Context;
 use crate::dbs::Iterable;
 use crate::sql::{Explain, Object, Value};
 use std::collections::HashMap;
@@ -6,7 +7,11 @@ use std::collections::HashMap;
 pub(super) struct Explanation(Vec<ExplainItem>);
 
 impl Explanation {
-	pub(super) fn new(e: Option<&Explain>, iterables: &Vec<Iterable>) -> (bool, Option<Self>) {
+	pub(super) fn new(
+		ctx: &Context<'_>,
+		e: Option<&Explain>,
+		iterables: &Vec<Iterable>,
+	) -> (bool, Option<Self>) {
 		match e {
 			None => (true, None),
 			Some(e) => {
@@ -14,6 +19,11 @@ impl Explanation {
 				for i in iterables {
 					exp.add_iter(i);
 				}
+				if let Some(qp) = ctx.get_query_planner() {
+					for reason in qp.fallbacks() {
+						exp.add_fallback(reason.to_string());
+					}
+				}
 				(e.0, Some(exp))
 			}
 		}
@@ -27,6 +37,10 @@ impl Explanation {
 		self.0.push(ExplainItem::new_fetch(count));
 	}
 
+	fn add_fallback(&mut self, reason: String) {
+		self.0.push(ExplainItem::new_fallback(reason));
+	}
+
 	pub(super) fn output(self, results: &mut Vec<Value>) {
 		for e in self.0 {
 			results.push(e.into());
@@ -47,6 +61,13 @@ impl ExplainItem {
 		}
 	}
 
+	fn new_fallback(reason: String) -> Self {
+		Self {
+			name: "Fallback".into(),
+			details: vec![("reason", reason.into())],
+		}
+	}
+
 	fn new_iter(iter: &Iterable) -> Self {
 		match iter {
 			Iterable::Value(v) => Self {

lib/src/dbs/iterator.rs

@@ -278,7 +278,7 @@ impl Iterator {
 		// Process the query START clause
 		self.setup_start(&cancel_ctx, opt, txn, stm).await?;
 		// Extract the expected behaviour depending on the presence of EXPLAIN with or without FULL
-		let (do_iterate, mut explanation) = Explanation::new(stm.explain(), &self.entries);
+		let (do_iterate, mut explanation) = Explanation::new(ctx, stm.explain(), &self.entries);
 
 		if do_iterate {
 			// Process prepared values

lib/src/doc/index.rs

@@ -57,7 +57,7 @@ impl<'a> Document<'a> {
 					Index::Search(p) => ic.index_full_text(&mut run, p).await?,
 					Index::MTree(_) => {
 						return Err(Error::FeatureNotYetImplemented {
-							feature: "MTree indexing",
+							feature: "MTree indexing".to_string(),
 						})
 					}
 				};

lib/src/err/mod.rs

@@ -606,7 +606,7 @@ pub enum Error {
 	/// The feature has not yet being implemented
 	#[error("Feature not yet implemented: {feature}")]
 	FeatureNotYetImplemented {
-		feature: &'static str,
+		feature: String,
 	},
 
 	/// Duplicated match references are not allowed

lib/src/fnc/string.rs

@@ -140,13 +140,13 @@ pub mod distance {
 
 	pub fn hamming((_, _): (String, String)) -> Result<Value, Error> {
 		Err(Error::FeatureNotYetImplemented {
-			feature: "string::distance::hamming() function",
+			feature: "string::distance::hamming() function".to_string(),
 		})
 	}
 
 	pub fn levenshtein((_, _): (String, String)) -> Result<Value, Error> {
 		Err(Error::FeatureNotYetImplemented {
-			feature: "string::distance::levenshtein() function",
+			feature: "string::distance::levenshtein() function".to_string(),
 		})
 	}
 }
@@ -234,7 +234,7 @@ pub mod similarity {
 
 	pub fn jaro((_, _): (String, String)) -> Result<Value, Error> {
 		Err(Error::FeatureNotYetImplemented {
-			feature: "string::similarity::jaro() function",
+			feature: "string::similarity::jaro() function".to_string(),
 		})
 	}
 

lib/src/fnc/vector.rs

@@ -66,7 +66,7 @@ pub mod distance {
 
 	pub fn mahalanobis((_, _): (Vec<Number>, Vec<Number>)) -> Result<Value, Error> {
 		Err(Error::FeatureNotYetImplemented {
-			feature: "vector::distance::mahalanobis() function",
+			feature: "vector::distance::mahalanobis() function".to_string(),
 		})
 	}
 
@@ -99,7 +99,7 @@ pub mod similarity {
 
 	pub fn spearman((_, _): (Vec<Number>, Vec<Number>)) -> Result<Value, Error> {
 		Err(Error::FeatureNotYetImplemented {
-			feature: "vector::similarity::spearman() function",
+			feature: "vector::similarity::spearman() function".to_string(),
 		})
 	}
 }

lib/src/idx/planner/executor.rs

@@ -122,7 +122,7 @@ impl QueryExecutor {
 				..
 			} => self.new_search_index_iterator(ir, io).await,
 			_ => Err(Error::FeatureNotYetImplemented {
-				feature: "VectorSearch iterator",
+				feature: "VectorSearch iterator".to_string(),
 			}),
 		}
 	}

lib/src/idx/planner/mod.rs

@@ -20,6 +20,7 @@ pub(crate) struct QueryPlanner<'a> {
 	/// There is one executor per table
 	executors: HashMap<String, QueryExecutor>,
 	requires_distinct: bool,
+	fallbacks: Vec<String>,
 }
 
 impl<'a> QueryPlanner<'a> {
@@ -30,6 +31,7 @@ impl<'a> QueryPlanner<'a> {
 			cond,
 			executors: HashMap::default(),
 			requires_distinct: false,
+			fallbacks: vec![],
 		}
 	}
 
@@ -40,31 +42,36 @@ impl<'a> QueryPlanner<'a> {
 		t: Table,
 		it: &mut Iterator,
 	) -> Result<(), Error> {
-		let res = Tree::build(ctx, self.opt, txn, &t, self.cond).await?;
-		if let Some((node, im)) = res {
-			let mut exe = QueryExecutor::new(self.opt, txn, &t, im).await?;
-			let ok = match PlanBuilder::build(node, self.with)? {
-				Plan::SingleIndex(exp, io) => {
-					let ir = exe.add_iterator(exp);
-					it.ingest(Iterable::Index(t.clone(), ir, io));
-					true
-				}
-				Plan::MultiIndex(v) => {
-					for (exp, io) in v {
+		match Tree::build(ctx, self.opt, txn, &t, self.cond).await? {
+			Some((node, im)) => {
+				let mut exe = QueryExecutor::new(self.opt, txn, &t, im).await?;
+				match PlanBuilder::build(node, self.with)? {
+					Plan::SingleIndex(exp, io) => {
 						let ir = exe.add_iterator(exp);
 						it.ingest(Iterable::Index(t.clone(), ir, io));
-						self.requires_distinct = true;
+						self.executors.insert(t.0.clone(), exe);
+					}
+					Plan::MultiIndex(v) => {
+						for (exp, io) in v {
+							let ir = exe.add_iterator(exp);
+							it.ingest(Iterable::Index(t.clone(), ir, io));
+							self.requires_distinct = true;
+						}
+						self.executors.insert(t.0.clone(), exe);
+					}
+					Plan::TableIterator(fallback) => {
+						if let Some(fallback) = fallback {
+							self.fallbacks.push(fallback);
+						}
+						self.executors.insert(t.0.clone(), exe);
+						it.ingest(Iterable::Table(t));
 					}
-					true
 				}
-				Plan::TableIterator => false,
-			};
-			self.executors.insert(t.0.clone(), exe);
-			if ok {
-				return Ok(());
+			}
+			None => {
+				it.ingest(Iterable::Table(t));
 			}
 		}
-		it.ingest(Iterable::Table(t));
 		Ok(())
 	}
 
@@ -79,4 +86,8 @@ impl<'a> QueryPlanner<'a> {
 	pub(crate) fn requires_distinct(&self) -> bool {
 		self.requires_distinct
 	}
+
+	pub(crate) fn fallbacks(&self) -> &Vec<String> {
+		&self.fallbacks
+	}
 }

lib/src/idx/planner/plan.rs

@@ -20,7 +20,7 @@ impl<'a> PlanBuilder<'a> {
 	pub(super) fn build(root: Node, with: &'a Option<With>) -> Result<Plan, Error> {
 		if let Some(with) = with {
 			if matches!(with, With::NoIndex) {
-				return Ok(Plan::TableIterator);
+				return Ok(Plan::TableIterator(Some("WITH NOINDEX".to_string())));
 			}
 		}
 		let mut b = PlanBuilder {
@@ -30,12 +30,12 @@ impl<'a> PlanBuilder<'a> {
 			all_exp_with_index: true,
 		};
 		// Browse the AST and collect information
-		if !b.eval_node(root)? {
-			return Ok(Plan::TableIterator);
+		if let Err(e) = b.eval_node(root) {
+			return Ok(Plan::TableIterator(Some(e.to_string())));
 		}
 		// If we didn't found any index, we're done with no index plan
 		if b.indexes.is_empty() {
-			return Ok(Plan::TableIterator);
+			return Ok(Plan::TableIterator(Some("NO INDEX FOUND".to_string())));
 		}
 		// If every boolean operator are AND then we can use the single index plan
 		if b.all_and {
@@ -47,7 +47,7 @@ impl<'a> PlanBuilder<'a> {
 		if b.all_exp_with_index {
 			return Ok(Plan::MultiIndex(b.indexes));
 		}
-		Ok(Plan::TableIterator)
+		Ok(Plan::TableIterator(None))
 	}
 
 	// Check if we have an explicit list of index we can use
@@ -62,7 +62,7 @@ impl<'a> PlanBuilder<'a> {
 		io
 	}
 
-	fn eval_node(&mut self, node: Node) -> Result<bool, Error> {
+	fn eval_node(&mut self, node: Node) -> Result<(), String> {
 		match node {
 			Node::Expression {
 				io,
@@ -79,10 +79,12 @@ impl<'a> PlanBuilder<'a> {
 				} else if self.all_exp_with_index && !is_bool {
 					self.all_exp_with_index = false;
 				}
-				self.eval_expression(*left, *right)
+				self.eval_node(*left)?;
+				self.eval_node(*right)?;
+				Ok(())
 			}
-			Node::Unsupported => Ok(false),
-			_ => Ok(true),
+			Node::Unsupported(reason) => Err(reason),
+			_ => Ok(()),
 		}
 	}
 
@@ -99,23 +101,13 @@ impl<'a> PlanBuilder<'a> {
 		}
 	}
 
-	fn eval_expression(&mut self, left: Node, right: Node) -> Result<bool, Error> {
-		if !self.eval_node(left)? {
-			return Ok(false);
-		}
-		if !self.eval_node(right)? {
-			return Ok(false);
-		}
-		Ok(true)
-	}
-
 	fn add_index_option(&mut self, e: Expression, i: IndexOption) {
 		self.indexes.push((e, i));
 	}
 }
 
 pub(super) enum Plan {
-	TableIterator,
+	TableIterator(Option<String>),
 	SingleIndex(Expression, IndexOption),
 	MultiIndex(Vec<(Expression, IndexOption)>),
 }

lib/src/idx/planner/tree.rs

@@ -71,20 +71,20 @@ impl<'a> TreeBuilder<'a> {
 	#[cfg_attr(not(target_arch = "wasm32"), async_recursion)]
 	#[cfg_attr(target_arch = "wasm32", async_recursion(?Send))]
 	async fn eval_value(&mut self, v: &Value) -> Result<Node, Error> {
-		Ok(match v {
-			Value::Expression(e) => self.eval_expression(e).await?,
-			Value::Idiom(i) => self.eval_idiom(i).await?,
-			Value::Strand(_) => Node::Scalar(v.to_owned()),
-			Value::Number(_) => Node::Scalar(v.to_owned()),
-			Value::Bool(_) => Node::Scalar(v.to_owned()),
-			Value::Thing(_) => Node::Scalar(v.to_owned()),
-			Value::Subquery(s) => self.eval_subquery(s).await?,
+		match v {
+			Value::Expression(e) => self.eval_expression(e).await,
+			Value::Idiom(i) => self.eval_idiom(i).await,
+			Value::Strand(_) => Ok(Node::Scalar(v.to_owned())),
+			Value::Number(_) => Ok(Node::Scalar(v.to_owned())),
+			Value::Bool(_) => Ok(Node::Scalar(v.to_owned())),
+			Value::Thing(_) => Ok(Node::Scalar(v.to_owned())),
+			Value::Subquery(s) => self.eval_subquery(s).await,
 			Value::Param(p) => {
 				let v = p.compute(self.ctx, self.opt, self.txn, None).await?;
-				self.eval_value(&v).await?
+				self.eval_value(&v).await
 			}
-			_ => Node::Unsupported,
-		})
+			_ => Ok(Node::Unsupported(format!("Unsupported value: {}", v))),
+		}
 	}
 
 	async fn eval_idiom(&mut self, i: &Idiom) -> Result<Node, Error> {
@@ -99,9 +99,7 @@ impl<'a> TreeBuilder<'a> {
 		match e {
 			Expression::Unary {
 				..
-			} => Err(Error::FeatureNotYetImplemented {
-				feature: "unary expressions in index",
-			}),
+			} => Ok(Node::Unsupported("unary expressions not supported".to_string())),
 			Expression::Binary {
 				l,
 				o,
@@ -173,10 +171,10 @@ impl<'a> TreeBuilder<'a> {
 	}
 
 	async fn eval_subquery(&mut self, s: &Subquery) -> Result<Node, Error> {
-		Ok(match s {
-			Subquery::Value(v) => self.eval_value(v).await?,
-			_ => Node::Unsupported,
-		})
+		match s {
+			Subquery::Value(v) => self.eval_value(v).await,
+			_ => Ok(Node::Unsupported(format!("Unsupported subquery: {}", s))),
+		}
 	}
 }
 
@@ -201,7 +199,7 @@ pub(super) enum Node {
 	IndexedField(Idiom, DefineIndexStatement),
 	NonIndexedField,
 	Scalar(Value),
-	Unsupported,
+	Unsupported(String),
 }
 
 impl Node {

lib/src/sql/statements/analyze.rs

@@ -58,7 +58,7 @@ impl AnalyzeStatement {
 					}
 					_ => {
 						return Err(Error::FeatureNotYetImplemented {
-							feature: "Statistics on unique and non-unique indexes.",
+							feature: "Statistics on unique and non-unique indexes.".to_string(),
 						})
 					}
 				};

lib/tests/planner.rs

@@ -110,10 +110,10 @@ async fn select_where_iterate_two_no_index() -> Result<(), Error> {
 	let mut res = execute_test(&two_multi_index_query("WITH NOINDEX", ""), 9).await?;
 	// OR results
 	check_result(&mut res, "[{ name: 'Jaime' }, { name: 'Tobie' }]")?;
-	check_result(&mut res, &table_explain(2))?;
+	check_result(&mut res, &table_explain_no_index(2))?;
 	// AND results
 	check_result(&mut res, "[{name: 'Jaime'}]")?;
-	check_result(&mut res, &table_explain(1))?;
+	check_result(&mut res, &table_explain_no_index(1))?;
 	Ok(())
 }
 
@@ -185,6 +185,31 @@ fn table_explain(fetch_count: usize) -> String {
 	)
 }
 
+fn table_explain_no_index(fetch_count: usize) -> String {
+	format!(
+		"[
+			{{
+				detail: {{
+					table: 'person'
+				}},
+				operation: 'Iterate Table'
+			}},
+			{{
+				detail: {{
+					reason: 'WITH NOINDEX'
+				}},
+				operation: 'Fallback'
+			}},
+			{{
+				detail: {{
+					count: {fetch_count}
+				}},
+				operation: 'Fetch'
+			}}
+		]"
+	)
+}
+
 const THREE_TABLE_EXPLAIN: &str = "[
 	{
 		detail: {
@@ -332,3 +357,60 @@ const TWO_MULTI_INDEX_EXPLAIN: &str = "[
 					operation: 'Fetch'
 				}
 			]";
+
+#[tokio::test]
+async fn select_with_no_index_unary_operator() -> Result<(), Error> {
+	let dbs = new_ds().await?;
+	let ses = Session::owner().with_ns("test").with_db("test");
+	let mut res = dbs
+		.execute("SELECT * FROM table WITH NOINDEX WHERE !param.subparam EXPLAIN", &ses, None)
+		.await?;
+	assert_eq!(res.len(), 1);
+	let tmp = res.remove(0).result?;
+	let val = Value::parse(
+		r#"[
+				{
+					detail: {
+						table: 'table'
+					},
+					operation: 'Iterate Table'
+				},
+				{
+					detail: {
+						reason: 'WITH NOINDEX'
+					},
+					operation: 'Fallback'
+				}
+			]"#,
+	);
+	assert_eq!(format!("{:#}", tmp), format!("{:#}", val));
+	Ok(())
+}
+
+#[tokio::test]
+async fn select_unsupported_unary_operator() -> Result<(), Error> {
+	let dbs = new_ds().await?;
+	let ses = Session::owner().with_ns("test").with_db("test");
+	let mut res =
+		dbs.execute("SELECT * FROM table WHERE !param.subparam EXPLAIN", &ses, None).await?;
+	assert_eq!(res.len(), 1);
+	let tmp = res.remove(0).result?;
+	let val = Value::parse(
+		r#"[
+				{
+					detail: {
+						table: 'table'
+					},
+					operation: 'Iterate Table'
+				},
+				{
+					detail: {
+						reason: 'unary expressions not supported'
+					},
+					operation: 'Fallback'
+				}
+			]"#,
+	);
+	assert_eq!(format!("{:#}", tmp), format!("{:#}", val));
+	Ok(())
+}