feat(frontend): describe stmt shows index ordering (#8073)

- As title.

Approved-By: yezizp2012
Approved-By: cyliu0

Co-Authored-By: Dylan Chen <zilin@singularity-data.com>
Co-Authored-By: Dylan <chenzl25@mail2.sysu.edu.cn>

src/frontend/src/handler/describe.rs

@@ -29,6 +29,7 @@ use crate::binder::{Binder, Relation};
 use crate::catalog::{CatalogError, IndexCatalog};
 use crate::handler::util::col_descs_to_rows;
 use crate::handler::HandlerArgs;
+use crate::optimizer::property::Direction;
 
 pub fn handle_describe(handler_args: HandlerArgs, table_name: ObjectName) -> Result<RwPgResponse> {
     let session = handler_args.session;
@@ -113,11 +114,18 @@ pub fn handle_describe(handler_args: HandlerArgs, table_name: ObjectName) -> Res
     rows.extend(indices.iter().map(|index| {
         let index_table = index.index_table.clone();
 
-        let index_columns = index_table
+        let index_columns_with_ordering = index_table
             .pk
             .iter()
             .filter(|x| !index_table.columns[x.index].is_hidden)
-            .map(|x| index_table.columns[x.index].name().to_string())
+            .map(|x| {
+                let index_column_name = index_table.columns[x.index].name().to_string();
+                if Direction::Desc == x.direct {
+                    index_column_name + " DESC"
+                } else {
+                    index_column_name
+                }
+            })
             .collect_vec();
 
         let pk_column_index_set = index_table
@@ -147,7 +155,7 @@ pub fn handle_describe(handler_args: HandlerArgs, table_name: ObjectName) -> Res
                 Some(
                     format!(
                         "index({}) distributed by({})",
-                        display_comma_separated(&index_columns),
+                        display_comma_separated(&index_columns_with_ordering),
                         display_comma_separated(&distributed_by_columns),
                     )
                     .into(),
@@ -156,7 +164,7 @@ pub fn handle_describe(handler_args: HandlerArgs, table_name: ObjectName) -> Res
                 Some(
                     format!(
                         "index({}) include({}) distributed by({})",
-                        display_comma_separated(&index_columns),
+                        display_comma_separated(&index_columns_with_ordering),
                         display_comma_separated(&include_columns),
                         display_comma_separated(&distributed_by_columns),
                     )
@@ -204,7 +212,7 @@ mod tests {
             .unwrap();
 
         frontend
-            .run_sql("create index idx1 on t (v1,v2);")
+            .run_sql("create index idx1 on t (v1 DESC, v2);")
             .await
             .unwrap();
 
@@ -233,7 +241,7 @@ mod tests {
             "v3".into() => "Int32".into(),
             "v4".into() => "Int32".into(),
             "primary key".into() => "v3".into(),
-            "idx1".into() => "index(v1, v2, v3) include(v4) distributed by(v1, v2)".into(),
+            "idx1".into() => "index(v1 DESC, v2, v3) include(v4) distributed by(v1, v2)".into(),
         };
 
         assert_eq!(columns, expected_columns);