fix(postgres): bind the caller's schema in getTableColumns

backend/src/main/java/com/dbaagent/provider/postgres/PostgresIntrospectionProvider.java

@@ -166,24 +166,36 @@ SELECT n.nspname as schema_name, p.proname as name, pg_get_functiondef(p.oid) as
     public List<ColumnInfo> getTableColumns(Connection connection, String database, String tableName) throws SQLException {
         List<ColumnInfo> columns = new ArrayList<>();
 
+        // `database` carries the schema here: getTablesAndViews() passes the schema each
+        // row was found in. Binding DEFAULT_SCHEMA instead returned zero columns for every
+        // table on any database whose objects live outside public — and the unqualified PK
+        // subquery cross-matched same-named tables, since Postgres auto-names primary keys
+        // "<table>_pkey" and two schemas holding `orders` collide by construction.
+        String schema = (database == null || database.isBlank()) ? DEFAULT_SCHEMA : database;
+
         String query = """
             SELECT c.column_name, c.data_type, c.is_nullable, c.column_default,
                 CASE WHEN pk.column_name IS NOT NULL THEN true ELSE false END as is_primary_key
             FROM information_schema.columns c
             LEFT JOIN (
                 SELECT ku.column_name
                 FROM information_schema.table_constraints tc
-                JOIN information_schema.key_column_usage ku ON tc.constraint_name = ku.constraint_name
-                WHERE tc.constraint_type = 'PRIMARY KEY' AND ku.table_name = ?
+                JOIN information_schema.key_column_usage ku
+                  ON tc.constraint_name = ku.constraint_name
+                 AND tc.table_schema = ku.table_schema
+                WHERE tc.constraint_type = 'PRIMARY KEY'
+                  AND ku.table_name = ?
+                  AND ku.table_schema = ?
             ) pk ON c.column_name = pk.column_name
             WHERE c.table_name = ? AND c.table_schema = ?
             ORDER BY c.ordinal_position
             """;
 
         try (PreparedStatement stmt = connection.prepareStatement(query)) {
             stmt.setString(1, tableName);
-            stmt.setString(2, tableName);
-            stmt.setString(3, DEFAULT_SCHEMA);
+            stmt.setString(2, schema);
+            stmt.setString(3, tableName);
+            stmt.setString(4, schema);
             try (ResultSet rs = stmt.executeQuery()) {
                 while (rs.next()) {
                     ColumnInfo col = new ColumnInfo();