Tool for un-merging incorrectly merged locations

[simonw]

https://discord.com/channels/799147121357881364/824443781990187008/859157576117780520 - it turns out we have some locations that have been incorrectly merged and we need a tool to fix them.

[simonw]

For the moment I'll build this as a non-API tool - it will live at https://vial.calltheshots.us/admin/unmerge-locations/ to mirror the existing https://vial.calltheshots.us/admin/merge-locations/ tool.

[simonw]

Current merge locations tool implementation:

vial/vaccinate/core/tool_views.py

Lines 212 to 238 in 3aca574

	@login_required
	@user_passes_test(lambda user: user.has_perm("core.merge_locations"))
	def merge_locations_view(request):
	if request.method == "POST":
	winner, loser = get_winner_loser(request.POST)
	if (
	winner
	and loser
	and (winner.pk != loser.pk)
	and not (winner.soft_deleted or loser.soft_deleted)
	):
	# Merge them
	merge_locations(winner, loser, request.user)
	messages.success(request, "Locations merged")
	return HttpResponseRedirect(
	f"/admin/core/location/{winner.pk}/change/#location-h2"
	)
	else:
	winner, loser = get_winner_loser(request.GET)
	return render(
	request,
	"admin/merge_locations.html",
	{
	"winner": winner,
	"loser": loser,
	},
	)

Which calls this function:

vial/vaccinate/core/utils_merge_locations.py

Lines 7 to 52 in 3aca574

	def merge_locations(winner: Location, loser: Location, user: User):
	with reversion.create_revision():
	# Record details of prior state before merge for these things,
	# because they will not be automatically captured in the
	# reversion history for the Location records
	winner_concordances = [str(c) for c in winner.concordances.all()]
	loser_concordances = [str(c) for c in loser.concordances.all()]
	details = {
	"winner_report_ids": list(winner.reports.values_list("pk", flat=True)),
	"loser_report_ids": list(loser.reports.values_list("pk", flat=True)),
	"winner_matched_source_location_ids": list(
	winner.matched_source_locations.values_list("pk", flat=True)
	),
	"loser_matched_source_location_ids": list(
	loser.matched_source_locations.values_list("pk", flat=True)
	),
	"winner_concordances": winner_concordances,
	"loser_concordances": loser_concordances,
	}
	loser.reports.update(location=winner.pk)
	loser.matched_source_locations.update(matched_location=winner.pk)
	loser.soft_deleted = True
	loser.soft_deleted_because = "Merged into location {}".format(winner.public_id)
	loser.duplicate_of = winner
	loser.save()
	# Copy concordances from loser to winner
	missing_concordances = [
	c for c in loser_concordances if c not in winner_concordances
	]
	for concordance in missing_concordances:
	winner.concordances.add(ConcordanceIdentifier.for_idref(concordance))
	CompletedLocationMerge.objects.create(
	winner_location=winner,
	loser_location=loser,
	created_by=user,
	details=details,
	)
	reversion.set_user(user)
	reversion.set_comment(
	"Merged locations, winner = {}, loser = {}".format(
	winner.public_id, loser.public_id
	)
	)

The trickiest thing to unwind here is the reports and source locations that were re-pointed at the winner. Thankfully we record details of what happened here:

details = {
    "winner_report_ids": list(winner.reports.values_list("pk", flat=True)),
    "loser_report_ids": list(loser.reports.values_list("pk", flat=True)),
    "winner_matched_source_location_ids": list(
        winner.matched_source_locations.values_list("pk", flat=True)
    ),
    "loser_matched_source_location_ids": list(
        loser.matched_source_locations.values_list("pk", flat=True)
    ),
    "winner_concordances": winner_concordances,
    "loser_concordances": loser_concordances,
}

[simonw]

The completed_location_merge table has details of completed merges in it - 890 at the moment: https://vial.calltheshots.us/dashboard/?sql=select%20count%28%2A%29%20from%20completed_location_merge%3AQocwKRKE6sxqWu78c-dit_bsB8MuepN6sSulKqxHtOg&sql=select%20id%2C%20created_at%2C%20details%2C%20created_by_id%2C%20loser_location_id%2C%20task_id%2C%20winner_location_id%20from%20completed_location_merge%3A__UqR2yHbu5btq4pLNt8Fg8E8Qag7FR5-lohPJboDNQ