internal/integration: composite-index test case

internal/integration/testdata/postgres/index-desc.txt

@@ -7,6 +7,9 @@ cmpshow users 2.sql
 # Use of "columns" instead of "on" should not trigger a change.
 synced 2-no-change.hcl
 
+apply 3.hcl
+cmpshow users 3.sql
+
 -- 1.hcl --
 schema "$db" {}
 
@@ -54,6 +57,7 @@ table "users" {
 Indexes:
     "rank_idx" btree (rank)
 
+
 -- 2-no-change.hcl --
 schema "$db" {}
 
@@ -67,4 +71,36 @@ table "users" {
             table.users.column.rank,
         ]
     }
-}
+}
+
+
+-- 3.hcl --
+schema "$db" {}
+
+table "users" {
+    schema = schema.$db
+    column "rank" {
+        type = int
+    }
+    column "score" {
+        type = int
+    }
+    index "rank_score_idx" {
+        on {
+            column = table.users.column.rank
+        }
+        on {
+            column = table.users.column.score
+            desc = true
+        }
+    }
+}
+
+-- 3.sql --
+          Table "script_index_desc.users"
+ Column |  Type   | Collation | Nullable | Default
+--------+---------+-----------+----------+---------
+ rank   | integer |           | not null |
+ score  | integer |           | not null |
+Indexes:
+    "rank_score_idx" btree (rank, score DESC)