Fix adding extra unique constraint to columns that are already unique

examples/.ledger

@@ -47,3 +47,4 @@
 47_add_table_foreign_key_constraint.json
 48_drop_tickets_check.json
 49_unset_not_null_on_indexed_column.json
+50_add_extra_unique_constraint_to_fruits.json

examples/08_create_fruits_table.json

@@ -18,6 +18,10 @@
           {
             "name": "price",
             "type": "decimal(10,2)"
+          },
+          {
+            "name": "producer",
+            "type": "varchar(255)"
           }
         ]
       }

examples/50_add_extra_unique_constraint_to_fruits.json

@@ -0,0 +1,24 @@
+{
+  "name": "44_add_extra_unique_constraint_to_fruits",
+  "operations": [
+    {
+      "create_constraint": {
+        "type": "unique",
+        "table": "fruits",
+        "name": "unique_fruit_and_producer",
+        "columns": [
+          "name",
+          "producer"
+        ],
+        "up": {
+          "name": "name",
+          "producer": "producer"
+        },
+        "down": {
+          "name": "name",
+          "producer": "producer"
+        }
+      }
+    }
+  ]
+}

pkg/migrations/rename.go

@@ -123,26 +123,24 @@ func RenameDuplicatedColumn(ctx context.Context, conn db.DB, table *schema.Table
 	// Rename any indexes on the duplicated column and use unique indexes to
 	// create `UNIQUE` constraints.
 	for _, idx := range table.Indexes {
-		if !IsDuplicatedName(idx.Name) {
+		if !IsDuplicatedName(idx.Name) || !slices.Contains(idx.Columns, TemporaryName(column.Name)) {
 			continue
 		}
 
-		if slices.Contains(idx.Columns, TemporaryName(column.Name)) {
-			// Rename the index to its original name
-			renameIndexSQL := fmt.Sprintf(cRenameIndexSQL,
-				pq.QuoteIdentifier(idx.Name),
-				pq.QuoteIdentifier(StripDuplicationPrefix(idx.Name)),
-			)
+		// Rename the index to its original name
+		renameIndexSQL := fmt.Sprintf(cRenameIndexSQL,
+			pq.QuoteIdentifier(idx.Name),
+			pq.QuoteIdentifier(StripDuplicationPrefix(idx.Name)),
+		)
 
-			_, err = conn.ExecContext(ctx, renameIndexSQL)
-			if err != nil {
-				return fmt.Errorf("failed to rename index %q: %w", idx.Name, err)
-			}
-
-			// Index no longer exists, remove it from the table
-			delete(table.Indexes, idx.Name)
+		_, err = conn.ExecContext(ctx, renameIndexSQL)
+		if err != nil {
+			return fmt.Errorf("failed to rename index %q: %w", idx.Name, err)
 		}
 
+		// Index no longer exists, remove it from the table
+		delete(table.Indexes, idx.Name)
+
 		if _, ok := table.UniqueConstraints[StripDuplicationPrefix(idx.Name)]; idx.Unique && ok {
 			// Create a unique constraint using the unique index
 			createUniqueConstraintSQL := fmt.Sprintf(cCreateUniqueConstraintSQL,
@@ -156,7 +154,6 @@ func RenameDuplicatedColumn(ctx context.Context, conn db.DB, table *schema.Table
 				return fmt.Errorf("failed to create unique constraint from index %q: %w", idx.Name, err)
 			}
 		}
-
 	}
 
 	return nil