private String[] parseKey(String key) {
            if (key.contains(":")) {
                // split the group and bucket
                return new String[] {
                    StringUtils.substringBeforeLast(key, ":"),
                    StringUtils.substringAfterLast(key, ":"),
                };
            }
            return new String[] {"default", key};
        }
Build one heatmap value column based on rawdata in the storage and row id.

@param id      of the row
@param rawdata literal string, represent a {@link DataTable}
oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/query/type/HeatMap.java