public Builder columns(Collection<ClickHouseColumn> columns) {
            if (columns != null) {
                for (ClickHouseColumn c : columns) {
                    this.columns.add(c);
                }
            }
            return this;
        }
Sets deferred content.

@param content non-null deferred content
@return this builder
clickhouse-data/src/main/java/com/clickhouse/data/ClickHouseExternalTable.java