How would i go about converting the following raw query to the new on_conflict op?

[Drapersniper]

INSERT INTO player (id, bot, dj_roles)
VALUES ({}, {}, {})
ON CONFLICT (id, bot)
DO UPDATE 
SET dj_roles = array_cat(player.dj_roles, EXCLUDED.dj_roles);

[dantownsend]

Give this a go:

from piccolo.querystring import QueryString

await Player.insert(
    Player(...)  # Whichever rows you want to upsert
).on_conflict(
    action='DO UPDATE',
    target=(Player.id, Player.bot),  # assuming you have a composite unique constraint on these columns
    values=[(Player.dj_roles, QueryString('array_cat(player.dj_roles, EXCLUDED.dj_roles)')]
)

We're passing in the SQL for the value to update using QueryString. This isn't really documented anywhere, but QueryString is the building block of queries internally.

[Drapersniper]

Fantastic, thanks for clarifying. I didn't think of QueryString here.

Edit:
Just to close the loop in case anyone in the future search for it everything worked fine with Dans suggestion with a small syntax fix.

from piccolo.querystring import QueryString

await Player.insert(
    Player(...)  # Whichever rows you want to upsert
).on_conflict(
    action='DO UPDATE',
    target=(Player.id, Player.bot),  # assuming you have a composite unique constraint on these columns
-    values=[(Player.dj_roles, QueryString('array_cat(player.dj_roles, EXCLUDED.dj_roles)')]
+    values=[(Player.dj_roles, QueryString('array_cat(player.dj_roles, EXCLUDED.dj_roles)'))]
)