Previously, a depth:0 query produced an empty report (since there are no
level zero accounts). Now, it aggregates all data into one summary item
with account name "...".
This makes it easier to see the kind of data Gwern was looking for from
register-csv (net worth over time). Eg this shows one line per month
summarising the total of assets and liabilities:
hledger register-csv -- -MHE ^assets ^liabilities depth:0
Single and multi-column balance reports behave similarly.
This refactoring fixes an O(n^2) slowdown in the balance command with
large numbers of accounts. It's now speedy, and the implementation is
clearer. To facilitate this, the Account type now represents a tree of
accounts which can easily be traversed up or down (and/or flattened
into a list).
Benchmark on a 2010 macbook:
+-------------------------------------------++--------------+------------+--------+
| || before: | after: | |
| || hledger-0.18 | hledgeropt | ledger |
+===========================================++==============+============+========+
| -f data/100x100x10.journal balance || 0.21 | 0.07 | 0.09 |
| -f data/1000x1000x10.journal balance || 10.13 | 0.47 | 0.62 |
| -f data/1000x10000x10.journal balance || 40.67 | 0.67 | 1.01 |
| -f data/10000x1000x10.journal balance || 15.01 | 3.22 | 2.36 |
| -f data/10000x1000x10.journal balance aa || 4.77 | 4.40 | 2.33 |
+-------------------------------------------++--------------+------------+--------+
