fix(frontend): require primary key for system table

e2e_test/batch/catalog/pg_settings.slt.part

@@ -63,6 +63,14 @@ query TT
 SELECT * FROM pg_catalog.pg_settings where name='dummy';
 ----
 
+# https://github.com/risingwavelabs/risingwave/issues/15125
+query TT
+SELECT min(name) name, context FROM pg_catalog.pg_settings GROUP BY context;
+----
+application_name            user
+backup_storage_directory    postmaster
+block_size_kb               internal
+
 # Tab-completion of `SET` command
 query T
 SELECT name

src/common/fields-derive/src/gen/test_empty_pk.rs

@@ -0,0 +1,29 @@
+impl ::risingwave_common::types::Fields for Data {
+    const PRIMARY_KEY: Option<&'static [usize]> = Some(&[]);
+    fn fields() -> Vec<(&'static str, ::risingwave_common::types::DataType)> {
+        vec![
+            ("v1", < i16 as ::risingwave_common::types::WithDataType >
+            ::default_data_type()), ("v2", < String as
+            ::risingwave_common::types::WithDataType > ::default_data_type())
+        ]
+    }
+    fn into_owned_row(self) -> ::risingwave_common::row::OwnedRow {
+        ::risingwave_common::row::OwnedRow::new(
+            vec![
+                ::risingwave_common::types::ToOwnedDatum::to_owned_datum(self.v1),
+                ::risingwave_common::types::ToOwnedDatum::to_owned_datum(self.v2)
+            ],
+        )
+    }
+}
+impl From<Data> for ::risingwave_common::types::ScalarImpl {
+    fn from(v: Data) -> Self {
+        ::risingwave_common::types::StructValue::new(
+                vec![
+                    ::risingwave_common::types::ToOwnedDatum::to_owned_datum(v.v1),
+                    ::risingwave_common::types::ToOwnedDatum::to_owned_datum(v.v2)
+                ],
+            )
+            .into()
+    }
+}

src/common/fields-derive/src/gen/test_no_pk.rs

@@ -0,0 +1,29 @@
+impl ::risingwave_common::types::Fields for Data {
+    const PRIMARY_KEY: Option<&'static [usize]> = None;
+    fn fields() -> Vec<(&'static str, ::risingwave_common::types::DataType)> {
+        vec![
+            ("v1", < i16 as ::risingwave_common::types::WithDataType >
+            ::default_data_type()), ("v2", < String as
+            ::risingwave_common::types::WithDataType > ::default_data_type())
+        ]
+    }
+    fn into_owned_row(self) -> ::risingwave_common::row::OwnedRow {
+        ::risingwave_common::row::OwnedRow::new(
+            vec![
+                ::risingwave_common::types::ToOwnedDatum::to_owned_datum(self.v1),
+                ::risingwave_common::types::ToOwnedDatum::to_owned_datum(self.v2)
+            ],
+        )
+    }
+}
+impl From<Data> for ::risingwave_common::types::ScalarImpl {
+    fn from(v: Data) -> Self {
+        ::risingwave_common::types::StructValue::new(
+                vec![
+                    ::risingwave_common::types::ToOwnedDatum::to_owned_datum(v.v1),
+                    ::risingwave_common::types::ToOwnedDatum::to_owned_datum(v.v2)
+                ],
+            )
+            .into()
+    }
+}

src/common/fields-derive/src/gen/test_output.rs

@@ -1,4 +1,5 @@
 impl ::risingwave_common::types::Fields for Data {
+    const PRIMARY_KEY: Option<&'static [usize]> = Some(&[1usize, 0usize]);
     fn fields() -> Vec<(&'static str, ::risingwave_common::types::DataType)> {
         vec![
             ("v1", < i16 as ::risingwave_common::types::WithDataType >
@@ -21,9 +22,6 @@ impl ::risingwave_common::types::Fields for Data {
             ],
         )
     }
-    fn primary_key() -> &'static [usize] {
-        &[1usize, 0usize]
-    }
 }
 impl From<Data> for ::risingwave_common::types::ScalarImpl {
     fn from(v: Data) -> Self {

src/common/fields-derive/src/lib.rs

@@ -66,16 +66,17 @@ fn gen(tokens: TokenStream) -> Result<TokenStream> {
         .iter()
         .map(|field| field.ident.as_ref().expect("field no name"))
         .collect::<Vec<_>>();
-    let primary_key = get_primary_key(&input).map(|indices| {
-        quote! {
-            fn primary_key() -> &'static [usize] {
-                &[#(#indices),*]
-            }
-        }
-    });
+    let primary_key = get_primary_key(&input).map_or_else(
+        || quote! { None },
+        |indices| {
+            quote! { Some(&[#(#indices),*]) }
+        },
+    );
 
     Ok(quote! {
         impl ::risingwave_common::types::Fields for #ident {
+            const PRIMARY_KEY: Option<&'static [usize]> = #primary_key;
+
             fn fields() -> Vec<(&'static str, ::risingwave_common::types::DataType)> {
                 vec![#(#fields_rw),*]
             }
@@ -84,7 +85,6 @@ fn gen(tokens: TokenStream) -> Result<TokenStream> {
                     ::risingwave_common::types::ToOwnedDatum::to_owned_datum(self.#names)
                 ),*])
             }
-            #primary_key
         }
         impl From<#ident> for ::risingwave_common::types::ScalarImpl {
             fn from(v: #ident) -> Self {
@@ -117,7 +117,9 @@ fn get_primary_key(input: &syn::DeriveInput) -> Option<Vec<usize>> {
         return Some(
             keys.to_string()
                 .split(',')
-                .map(|s| index(s.trim()))
+                .map(|s| s.trim())
+                .filter(|s| !s.is_empty())
+                .map(index)
                 .collect(),
         );
     }
@@ -143,6 +145,18 @@ mod tests {
         prettyplease::unparse(&output)
     }
 
+    fn do_test(code: &str, expected_path: &str) {
+        let input: TokenStream = str::parse(code).unwrap();
+
+        let output = super::gen(input).unwrap();
+
+        let output = pretty_print(output);
+
+        let expected = expect_test::expect_file![expected_path];
+
+        expected.assert_eq(&output);
+    }
+
     #[test]
     fn test_gen() {
         let code = indoc! {r#"
@@ -157,14 +171,33 @@ mod tests {
             }
         "#};
 
-        let input: TokenStream = str::parse(code).unwrap();
+        do_test(code, "gen/test_output.rs");
+    }
 
-        let output = super::gen(input).unwrap();
+    #[test]
+    fn test_no_pk() {
+        let code = indoc! {r#"
+            #[derive(Fields)]
+            struct Data {
+                v1: i16,
+                v2: String,
+            }
+        "#};
 
-        let output = pretty_print(output);
+        do_test(code, "gen/test_no_pk.rs");
+    }
 
-        let expected = expect_test::expect_file!["gen/test_output.rs"];
+    #[test]
+    fn test_empty_pk() {
+        let code = indoc! {r#"
+            #[derive(Fields)]
+            #[primary_key()]
+            struct Data {
+                v1: i16,
+                v2: String,
+            }
+        "#};
 
-        expected.assert_eq(&output);
+        do_test(code, "gen/test_empty_pk.rs");
     }
 }

src/common/src/types/fields.rs

@@ -58,17 +58,18 @@ use crate::util::chunk_coalesce::DataChunkBuilder;
 /// }
 /// ```
 pub trait Fields {
+    /// The primary key of the table.
+    ///
+    /// - `None` if the primary key is not applicable.
+    /// - `Some(&[])` if the primary key is empty, i.e., there'll be at most one row in the table.
+    const PRIMARY_KEY: Option<&'static [usize]>;
+
     /// Return the schema of the struct.
     fn fields() -> Vec<(&'static str, DataType)>;
 
     /// Convert the struct to an `OwnedRow`.
     fn into_owned_row(self) -> OwnedRow;
 
-    /// The primary key of the table.
-    fn primary_key() -> &'static [usize] {
-        &[]
-    }
-
     /// Create a [`DataChunkBuilder`](crate::util::chunk_coalesce::DataChunkBuilder) with the schema of the struct.
     fn data_chunk_builder(capacity: usize) -> DataChunkBuilder {
         DataChunkBuilder::new(

src/frontend/macro/src/lib.rs

@@ -117,11 +117,15 @@ fn gen_sys_table(attr: Attr, item_fn: ItemFn) -> Result<TokenStream2> {
         #[linkme::distributed_slice(crate::catalog::system_catalog::SYS_CATALOGS_SLICE)]
         #[no_mangle]    // to prevent duplicate schema.table name
         fn #gen_fn_name() -> crate::catalog::system_catalog::BuiltinCatalog {
+            const _: () = {
+                assert!(#struct_type::PRIMARY_KEY.is_some(), "primary key is required for system table");
+            };
+
             crate::catalog::system_catalog::BuiltinCatalog::Table(crate::catalog::system_catalog::BuiltinTable {
                 name: #table_name,
                 schema: #schema_name,
                 columns: #struct_type::fields(),
-                pk: #struct_type::primary_key(),
+                pk: #struct_type::PRIMARY_KEY.unwrap(),
                 function: |reader| std::boxed::Box::pin(async {
                     let rows = #user_fn_name(reader) #_await #handle_error;
                     let mut builder = #struct_type::data_chunk_builder(rows.len() + 1);

src/frontend/src/catalog/system_catalog/pg_catalog/pg_cast.rs

@@ -22,6 +22,7 @@ use crate::expr::cast_map_array;
 /// Ref: [`https://www.postgresql.org/docs/current/catalog-pg-cast.html`]
 #[derive(Fields)]
 struct PgCast {
+    #[primary_key]
     oid: i32,
     castsource: i32,
     casttarget: i32,

src/frontend/src/catalog/system_catalog/pg_catalog/pg_settings.rs

@@ -21,6 +21,7 @@ use crate::catalog::system_catalog::SysCatalogReaderImpl;
 /// The catalog `pg_settings` stores settings.
 /// Ref: [`https://www.postgresql.org/docs/current/view-pg-settings.html`]
 #[derive(Fields)]
+#[primary_key(name, context)]
 struct PgSetting {
     name: String,
     setting: String,

src/frontend/src/catalog/system_catalog/rw_catalog/rw_hummock_branched_objects.rs

@@ -19,6 +19,7 @@ use crate::catalog::system_catalog::SysCatalogReaderImpl;
 use crate::error::Result;
 
 #[derive(Fields)]
+#[primary_key(object_id, sst_id)] // TODO: is this correct?
 struct RwHummockBranchedObject {
     object_id: i64,
     sst_id: i64,

src/frontend/src/catalog/system_catalog/rw_catalog/rw_hummock_pinned_snapshots.rs

@@ -20,6 +20,7 @@ use crate::error::Result;
 
 #[derive(Fields)]
 struct RwHummockPinnedSnapshot {
+    #[primary_key]
     worker_node_id: i32,
     min_pinned_snapshot_id: i64,
 }

src/frontend/src/catalog/system_catalog/rw_catalog/rw_hummock_pinned_versions.rs

@@ -20,6 +20,7 @@ use crate::error::Result;
 
 #[derive(Fields)]
 struct RwHummockPinnedVersion {
+    #[primary_key]
     worker_node_id: i32,
     min_pinned_version_id: i64,
 }

src/frontend/src/catalog/system_catalog/rw_catalog/rw_hummock_version.rs

@@ -22,6 +22,7 @@ use crate::error::Result;
 
 #[derive(Fields)]
 struct RwHummockVersion {
+    #[primary_key]
     version_id: i64,
     max_committed_epoch: i64,
     safe_epoch: i64,

src/frontend/src/catalog/system_catalog/rw_catalog/rw_meta_snapshot.rs

@@ -21,6 +21,7 @@ use crate::error::Result;
 
 #[derive(Fields)]
 struct RwMetaSnapshot {
+    #[primary_key]
     meta_snapshot_id: i64,
     hummock_version_id: i64,
     // the smallest epoch this meta snapshot includes