docs: HashMap<String, byte[]> getExplainPlans(Catalog catalog) {
          HashMap<String, byte[]> retval = new HashMap<>();
          Database db = getCatalogDatabase(m_catalog);
          assert(db != null);
          for (Procedure proc : db.getProcedures()) {
              for (Statement stmt : proc.getStatements()) {
                  String s = "SQL: " + stmt.getSqltext() + "\n";
                  s += "COST: " + Integer.toString(stmt.getCost()) + "\n";
                  s += "PLAN:\n\n";
                  s += Encoder.hexDecodeToString(stmt.getExplainplan()) + "\n";
                  byte[] b = s.getBytes(Constants.UTF8ENCODING);
                  retval.put(proc.getTypeName() + "_" + stmt.getTypeName() + ".txt", b);
              }
          }
          return retval;
      }