add_index = async (table_name, field_name) => {
  // TBD check that there are no problems with lenght of constraint name
  const sql = `create index "${sqlsanitize(table_name)}_${sqlsanitize(
    field_name
  )}_index" on "${getTenantSchema()}"."${sqlsanitize(
    table_name
  )}" ("${sqlsanitize(field_name)}");`;
  sql_log(sql);
  await getMyClient().query(sql);
}
Add index
@param {string} table_name - table name
@param {string} field_name - list of columns (members of constraint)
@returns {Promise<void>} no result