We introduced task subtypes in T93499 / T224417.
I don't understand what some subtypes are good for, especially `deadline`. Deadline is not a task type.
Many task types can have a due date though.
Deadline is set/used by forms 37, 54 and 94.
Some tasks get created with the Deadline subtype and I have no idea why. They do not have any Due Dates. Examples: `T332743`, `T334770`, `T197015`.
Need to check though which edit forms allow setting/editing a Due Date on a task. Unfortunately Phab doesn't offer a simple way to check which form was used to create a task.
```
mysql:phstats@m3-slave.eqiad.wmnet [phabricator_maniphest]> SELECT mt.subtype, COUNT(mt.id) FROM phabricator_maniphest.maniphest_task mt GROUP BY mt.subtype;
+----------+--------------+
| subtype | COUNT(mt.id) |
+----------+--------------+
| bug | 11458 |
| deadline | 1116 |
| default | 308486 |
| design | 76 |
| error | 3440 |
| feature | 5981 |
| goal | 36 |
| release | 334 |
| request | 1701 |
| security | redacted |
| spike | 608 |
+----------+--------------+
11 rows in set (0.145 sec)
mysql:phstats@m3-slave.eqiad.wmnet [phabricator_maniphest]> SELECT mt.subtype, COUNT(mt.id) FROM phabricator_maniphest.maniphest_task mt WHERE (mt.status="open" OR mt.status="progress" OR mt.status="stalled") GROUP BY mt.subtype;
+----------+--------------+
| subtype | COUNT(mt.id) |
+----------+--------------+
| bug | 3523 |
| deadline | 82 |
| default | 44111 |
| design | 23 |
| error | 259 |
| feature | 4789 |
| goal | 12 |
| release | 10 |
| request | 75 |
| security | redacted |
| spike | 183 |
+----------+--------------+
11 rows in set (0.584 sec)
**Related issues:**
* {T310188}
* comments in {T355307}
* {T335367}
* {T379376}
* maybe also {T367830}.