public String getTagValue(final String tagName) {
        Integer tagPos = tagPositionMap.get(tagName);
        if (tagPos == null) {
            throw new RuntimeException(String.format("Tag with name [%s] could not be found", tagName));
        }
        try {
            return tagList.get(tagPos).getValue();
        } catch (final RuntimeException e) {
            throw new RuntimeException(String.format("Error extracting value for tag [%s] at position [%s]",
                    tagName, tagPos), e);
        }
    }
@param tagName The name of the tag in a {@link StatisticTag} object
@return The position of the tag in the tag list (0 based)
stroom-statistics/stroom-statistics-impl-sql/src/main/java/stroom/statistics/impl/sql/TimeAgnosticStatisticEvent.java