Idea: Show measure of size of transactions in journal view

[zroug]

It would be great to have a measure of the size of transactions in the journal view, similar to the "Change" column in the account view. Something similar to the following BQL query could be used to calculate the size of a transaction:

SELECT
  first(date) AS date,
  first(narration) AS narration,
  sum(units(position)) AS size
WHERE number(units(position)) >= 0
GROUP BY id

This only makes sense for transactions that are balanced, for unbalanced transactions this value should not be displayed. For multi-currency transactions, one could either display all currencies or ignore them too.

[yagebu]

I like the idea - a PR contributing this would be welcome :)