feat(psl): add validation + warning on missing indexes for relationMode = "prisma"

psl/builtin-connectors/src/mongodb.rs

@@ -132,4 +132,9 @@ impl Connector for MongoDbDatamodelConnector {
     fn allowed_relation_mode_settings(&self) -> enumflags2::BitFlags<RelationMode> {
         RelationMode::Prisma.into()
     }
+
+    /// Avoid checking whether the fields appearing in a `@relation` attribute are included in an index.
+    fn should_suggest_missing_referencing_fields_indexes(&self) -> bool {
+        false
+    }
 }

psl/diagnostics/Cargo.toml

@@ -6,3 +6,4 @@ edition = "2021"
 [dependencies]
 colored = "2"
 pest = "2.1.3"
+indoc = "1"

psl/diagnostics/src/warning.rs

@@ -1,9 +1,9 @@
-use colored::{ColoredString, Colorize};
-
 use crate::{
     pretty_print::{pretty_print, DiagnosticColorer},
     Span,
 };
+use colored::{ColoredString, Colorize};
+use indoc::indoc;
 
 /// A non-fatal warning emitted by the schema parser.
 /// For fancy printing, please use the `pretty_print_error` function.
@@ -25,6 +25,15 @@ impl DatamodelWarning {
         Self::new(message, span)
     }
 
+    pub fn new_missing_index_on_emulated_relation(span: Span) -> DatamodelWarning {
+        let message = indoc! {
+            r#"With `relationMode = \"prisma\"`, no foreign keys are used, so relation fields will not benefit from the index usually created by the relational database under the hood.
+            This can lead to poor performance when querying these fields. We recommend adding an index manually.
+            Learn more at https://pris.ly/d/relation-mode#indexes"#
+        };
+        Self::new(message.to_owned(), span)
+    }
+
     /// The user-facing warning message.
     pub fn message(&self) -> &str {
         &self.message

psl/parser-database/src/walkers/relation_field.rs

@@ -170,12 +170,12 @@ impl<'db> RelationFieldWalker<'db> {
     }
 
     /// The fields in the `fields: [...]` argument in the forward relation field.
-    pub fn referencing_fields(self) -> Option<impl ExactSizeIterator<Item = ScalarFieldWalker<'db>>> {
+    pub fn referencing_fields(self) -> Option<impl ExactSizeIterator<Item = ScalarFieldWalker<'db>> + Clone> {
         self.fields()
     }
 
     /// The fields in the `fields: [...]` argument in the forward relation field.
-    pub fn fields(self) -> Option<impl ExactSizeIterator<Item = ScalarFieldWalker<'db>>> {
+    pub fn fields(self) -> Option<impl ExactSizeIterator<Item = ScalarFieldWalker<'db>> + Clone> {
         let model_id = self.model_id;
         let attributes = self.attributes();
         attributes.fields.as_ref().map(move |fields| {

psl/psl-core/src/datamodel_connector.rs

@@ -299,6 +299,12 @@ pub trait Connector: Send + Sync {
         self.has_capability(ConnectorCapability::RelationFieldsInArbitraryOrder)
     }
 
+    /// If true, the schema validator function checks whether the referencing fields in a `@relation` attribute
+    /// are included in an index.
+    fn should_suggest_missing_referencing_fields_indexes(&self) -> bool {
+        true
+    }
+
     fn native_type_to_string(&self, instance: &NativeTypeInstance) -> String {
         let (name, args) = self.native_type_to_parts(instance);
         let args = if args.is_empty() {

psl/psl-core/src/validate/validation_pipeline/context.rs

@@ -2,7 +2,7 @@ use crate::{
     datamodel_connector::{Connector, RelationMode},
     Datasource, PreviewFeature,
 };
-use diagnostics::{DatamodelError, Diagnostics};
+use diagnostics::{DatamodelError, DatamodelWarning, Diagnostics};
 use enumflags2::BitFlags;
 
 /// The validation context. The lifetime parameter is _not_ the AST lifetime, but the subtype of
@@ -24,4 +24,9 @@ impl Context<'_> {
     pub(super) fn push_error(&mut self, error: DatamodelError) {
         self.diagnostics.push_error(error);
     }
+
+    /// Pure convenience method. Forwards to Diagnostics::push_warning().
+    pub(super) fn push_warning(&mut self, warning: DatamodelWarning) {
+        self.diagnostics.push_warning(warning);
+    }
 }

psl/psl-core/src/validate/validation_pipeline/validations.rs

@@ -97,6 +97,7 @@ pub(super) fn validate(ctx: &mut Context<'_>) {
             relation_fields::ignored_related_model(field, ctx);
             relation_fields::referential_actions(field, ctx);
             relation_fields::map(field, ctx);
+            relation_fields::validate_missing_relation_indexes(field, ctx);
         }
 
         for index in model.indexes() {

psl/psl-core/src/validate/validation_pipeline/validations/relation_fields.rs

@@ -5,6 +5,7 @@ use crate::{
     diagnostics::DatamodelError,
     validate::validation_pipeline::context::Context,
 };
+use diagnostics::DatamodelWarning;
 use enumflags2::BitFlags;
 use itertools::Itertools;
 use parser_database::{
@@ -249,3 +250,67 @@ pub(super) fn map(field: RelationFieldWalker<'_>, ctx: &mut Context<'_>) {
         validate_db_name(field.model().name(), relation_attr, field.mapped_name(), ctx, false);
     }
 }
+
+pub(super) fn validate_missing_relation_indexes(relation_field: RelationFieldWalker<'_>, ctx: &mut Context<'_>) {
+    if !ctx.connector.should_suggest_missing_referencing_fields_indexes() || ctx.relation_mode != RelationMode::Prisma {
+        return;
+    }
+
+    if let Some(fields) = relation_field.referencing_fields() {
+        let model = relation_field.model();
+        // Considers all fields that should be part of an index in the given model, w.r.t. to left-wise inclusion.
+        let referencing_fields_it = fields.map(|field| field.field_id());
+
+        // Considers all groups of indexes explicitly declared in the given model.
+        // An index group can be:
+        // - a singleton (@unique or @id)
+        // - an ordered set (@@unique or @@index)
+        let index_field_groups = model.indexes();
+
+        let referencing_fields_appear_in_index = index_field_groups
+            .map(|index_walker| index_walker.fields().map(|index| index.field_id()))
+            .any(|index_fields_it| {
+                let fields_it = referencing_fields_it.clone();
+                is_leftwise_included_it(fields_it, index_fields_it)
+            });
+
+        if !referencing_fields_appear_in_index {
+            let ast_field = relation_field.ast_field();
+            let span = ast_field
+                .span_for_attribute("relation")
+                .unwrap_or_else(|| ast_field.span());
+            ctx.push_warning(DatamodelWarning::new_missing_index_on_emulated_relation(span));
+        }
+    }
+}
+
+/// An subgroup is left-wise included in a supergroup if the subgroup is contained in the supergroup, and all the entries of
+/// the left-most entries of the supergroup match the order of definitions of the subgroup.
+/// More formally: { x_1, x_2, ..., x_n } is left-wise included in { y_1, y_2, ..., y_m } if and only if
+/// n <= m and x_i = y_i for all i in [1, n].
+fn is_leftwise_included_it<T>(subgrop: impl ExactSizeIterator<Item = T>, supergroup: impl Iterator<Item = T>) -> bool
+where
+    T: PartialEq,
+{
+    supergroup.take(subgrop.len()).eq(subgrop)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::is_leftwise_included_it;
+    #[test]
+    fn test_is_left_wise_included() {
+        let item = vec![1, 2];
+        let group = vec![1, 2, 3, 4];
+        assert_eq!(is_leftwise_included_it(item.iter(), group.iter()), true);
+        let item = vec![1, 2, 3, 4];
+        let group = vec![1, 2, 3, 4];
+        assert_eq!(is_leftwise_included_it(item.iter(), group.iter()), true);
+        let item = vec![1, 2, 3, 4];
+        let group = vec![1, 2];
+        assert_eq!(is_leftwise_included_it(item.iter(), group.iter()), false);
+        let item = vec![2, 3];
+        let group = vec![1, 2, 3, 4];
+        assert_eq!(is_leftwise_included_it(item.iter(), group.iter()), false);
+    }
+}

psl/psl/tests/validation/attributes/index/missing_index_warning/mongodb.prisma

@@ -0,0 +1,17 @@
+// no missing relation index validation on mongodb.
+
+datasource db {
+    provider = "mongodb"
+    url = env("TEST_DATABASE_URL")
+}
+
+model SomeUser {
+    id String @id @map("_id") @default(auto()) @db.ObjectId
+    posts Post[]
+}
+
+model Post {
+    id String @id @map("_id") @default(auto()) @db.ObjectId
+    userId String
+    user SomeUser @relation(fields: [userId], references: [id])
+}

psl/psl/tests/validation/attributes/index/missing_index_warning/relation_mode_foreign_keys.prisma

@@ -0,0 +1,17 @@
+// no missing relation index validation on relationMode = "foreignKeys" / no relationMode at all.
+
+datasource db {
+    provider = "mysql"
+    url = env("TEST_DATABASE_URL")
+}
+
+model SomeUser {
+    id Int @id
+    posts Post[]
+}
+
+model Post {
+    id Int @id
+    userId Int
+    user SomeUser @relation(fields: [userId], references: [id])
+}

psl/psl/tests/validation/attributes/index/missing_index_warning/relation_mode_prisma/one_field_at_at_unique.prisma

@@ -0,0 +1,20 @@
+// no relation index validation warning on relationMode = "prisma" when a referenced field is already in @@unique.
+
+datasource db {
+    provider = "mysql"
+    url = env("TEST_DATABASE_URL")
+    relationMode = "prisma"
+}
+
+model SomeUser {
+    id Int @id
+    profile Profile?
+}
+
+model Profile {
+    id Int @id
+    userId Int
+    user SomeUser? @relation(fields: [userId], references: [id])
+
+    @@unique([userId])
+}

psl/psl/tests/validation/attributes/index/missing_index_warning/relation_mode_prisma/one_field_at_unique.prisma

@@ -0,0 +1,18 @@
+// no relation index validation warning on relationMode = "prisma" when a referenced field is already in @unique.
+
+datasource db {
+    provider = "mysql"
+    url = env("TEST_DATABASE_URL")
+    relationMode = "prisma"
+}
+
+model SomeUser {
+    id Int @id
+    profile Profile?
+}
+
+model Profile {
+    id Int @id
+    userId Int @unique
+    user SomeUser? @relation(fields: [userId], references: [id])
+}

psl/psl/tests/validation/attributes/index/missing_index_warning/relation_mode_prisma/one_field_no_index.prisma

@@ -0,0 +1,26 @@
+// add missing relation index validation warning on relationMode = "prisma".
+
+datasource db {
+    provider = "mysql"
+    url = env("TEST_DATABASE_URL")
+    relationMode = "prisma"
+}
+
+model SomeUser {
+    id Int @id
+    posts Post[]
+}
+
+model Post {
+    id Int @id
+    userId Int
+    user SomeUser @relation(fields: [userId], references: [id])
+}
+// warning: With `relationMode = \"prisma\"`, no foreign keys are used, so relation fields will not benefit from the index usually created by the relational database under the hood.
+// This can lead to poor performance when querying these fields. We recommend adding an index manually.
+// Learn more at https://pris.ly/d/relation-mode#indexes
+//   -->  schema.prisma:17
+//    | 
+// 16 |     userId Int
+// 17 |     user SomeUser @relation(fields: [userId], references: [id])
+//    | 

psl/psl/tests/validation/attributes/index/missing_index_warning/relation_mode_prisma/three_fields_index_leftmost.prisma

@@ -0,0 +1,34 @@
+// add missing relation index validation warning on relationMode = "prisma".
+
+datasource db {
+    provider = "mysql"
+    url = env("TEST_DATABASE_URL")
+    relationMode = "prisma"
+}
+
+model SomeUser {
+    idA Int
+    idB Int
+    idC Int
+    posts Post[]
+
+    @@id([idA, idB, idC])
+}
+
+model Post {
+    id Int @id
+    userIdA Int
+    userIdB Int
+    userIdC Int
+    user SomeUser @relation(fields: [userIdA, userIdB, userIdC], references: [idA, idB, idC])
+
+    @@index([userIdA, userIdB])
+}
+// warning: With `relationMode = \"prisma\"`, no foreign keys are used, so relation fields will not benefit from the index usually created by the relational database under the hood.
+// This can lead to poor performance when querying these fields. We recommend adding an index manually.
+// Learn more at https://pris.ly/d/relation-mode#indexes
+//   -->  schema.prisma:23
+//    | 
+// 22 |     userIdC Int
+// 23 |     user SomeUser @relation(fields: [userIdA, userIdB, userIdC], references: [idA, idB, idC])
+//    | 

psl/psl/tests/validation/attributes/index/missing_index_warning/relation_mode_prisma/three_fields_index_rightmost.prisma

@@ -0,0 +1,34 @@
+// add missing relation index validation warning on relationMode = "prisma".
+
+datasource db {
+    provider = "mysql"
+    url = env("TEST_DATABASE_URL")
+    relationMode = "prisma"
+}
+
+model SomeUser {
+    idA Int
+    idB Int
+    idC Int
+    posts Post[]
+
+    @@id([idA, idB, idC])
+}
+
+model Post {
+    id Int @id
+    userIdA Int
+    userIdB Int
+    userIdC Int
+    user SomeUser @relation(fields: [userIdA, userIdB, userIdC], references: [idA, idB, idC])
+
+    @@index([userIdB, userIdC])
+}
+// warning: With `relationMode = \"prisma\"`, no foreign keys are used, so relation fields will not benefit from the index usually created by the relational database under the hood.
+// This can lead to poor performance when querying these fields. We recommend adding an index manually.
+// Learn more at https://pris.ly/d/relation-mode#indexes
+//   -->  schema.prisma:23
+//    | 
+// 22 |     userIdC Int
+// 23 |     user SomeUser @relation(fields: [userIdA, userIdB, userIdC], references: [idA, idB, idC])
+//    | 

psl/psl/tests/validation/attributes/index/missing_index_warning/relation_mode_prisma/three_fields_mixed_unique.prisma

@@ -0,0 +1,34 @@
+// add missing relation index validation warning on relationMode = "prisma".
+
+datasource db {
+    provider = "mysql"
+    url = env("TEST_DATABASE_URL")
+    relationMode = "prisma"
+}
+
+model SomeUser {
+    idA Int
+    idB Int
+    idC Int
+    posts Post[]
+
+    @@id([idA, idB, idC])
+}
+
+model Post {
+    id Int @id
+    userIdA Int @unique
+    userIdB Int
+    userIdC Int @unique
+    user SomeUser @relation(fields: [userIdA, userIdB, userIdC], references: [idA, idB, idC])
+
+    @@unique([userIdA, userIdB])
+}
+// warning: With `relationMode = \"prisma\"`, no foreign keys are used, so relation fields will not benefit from the index usually created by the relational database under the hood.
+// This can lead to poor performance when querying these fields. We recommend adding an index manually.
+// Learn more at https://pris.ly/d/relation-mode#indexes
+//   -->  schema.prisma:23
+//    | 
+// 22 |     userIdC Int @unique
+// 23 |     user SomeUser @relation(fields: [userIdA, userIdB, userIdC], references: [idA, idB, idC])
+//    |