doc: comments

query-engine/connectors/sql-query-connector/src/filter/alias.rs

@@ -5,19 +5,22 @@ use crate::{model_extensions::AsColumn, *};
 use quaint::prelude::Column;
 use query_structure::ScalarField;
 
+/// An alias referring to a table or a join on a table.
 #[derive(Debug, Clone, Copy)]
 pub enum Alias {
     Table(usize),
     Join(usize),
 }
 
 impl Alias {
+    /// Converts the alias to one that refers to a join on the table.
     pub fn to_join_alias(self) -> Self {
         match self {
             Self::Table(index) | Self::Join(index) => Self::Join(index),
         }
     }
 
+    /// Converts the alias to one that refers to the table.
     pub fn to_table_alias(self) -> Self {
         match self {
             Self::Table(index) | Self::Join(index) => Self::Table(index),

query-engine/connectors/sql-query-connector/src/filter/visitor.rs

@@ -122,10 +122,10 @@ impl FilterVisitor {
     /// Traverses a relation filter using this rough SQL structure:
     ///
     /// ```sql
-    /// (parent.id) IN (
+    /// EXISTS (
     ///   SELECT id FROM parent
     ///   INNER JOIN child ON (child.parent_id = parent.id)
-    ///   WHERE <filter>
+    ///   WHERE <filter> AND outer.id = parent.id
     /// )
     /// ```
     /// We need this in two cases:
@@ -193,9 +193,9 @@ impl FilterVisitor {
     /// Traverses a relation filter using this rough SQL structure:
     ///
     /// ```sql
-    /// (parent.id1, parent.id2) IN (
+    /// EXISTS (
     ///   SELECT id1, id2 FROM child
-    ///   WHERE <filter>
+    ///   WHERE <filter> AND outer.id1 = child.id1 AND outer.id2 = child.id2
     /// )
     /// ```
     fn visit_relation_filter_select_with_row(&mut self, filter: RelationFilter, ctx: &Context<'_>) -> Select<'static> {