Remove redundant queries when importing closet pages

Specifically, we were running a find_or_initialize_by for all 50
hangers, which isn't great. Collation logic is more complicated this
way, but query count is way lower.

Additionally, compare against hanger.list_id instead of hanger.list,
because hanger.list will fire a query if list_id is non-nil, but that
nil ID tells us everything we needed to know, anyway.
This commit is contained in:
Emi Matchu 2013-06-26 00:10:52 -07:00
parent a7574f0864
commit b93dbb8e49

View file

@ -163,29 +163,56 @@ class ClosetPage
)
)
# Create closet hanger from each item, and remove them from the reference
# lists.
# And now for some more single-query beauty: check for existing hangers.
# We don't want to insert duplicate hangers of what a user owns if they
# already have it in another list (e.g. imports to Items You Own *after*
# curating their Up For Trade list), so we check for the hanger's presence
# in *all* items the user owns or wants (whichever is appropriate for this
# request).
hangers_scope = @user.closet_hangers.where(owned: @hangers_owned)
# Group existing hangers by item ID and whether they're from the current
# list or another list.
current_list_id = @closet_list.try(:id)
existing_hangers_by_item_id = hangers_scope.
where(item_id: items.map(&:id)).
group_by(&:item_id)
# Careful! We're just using a single default empty list for performance,
# but it must not be mutated! If mutation becomes necessary, change this
# to a default_proc assignment.
existing_hangers_by_item_id.default = []
# Create closet hanger from each item, and remove them from the reference
# lists.
@hangers = items.map do |item|
data = items_data[:id].delete(item.id) ||
items_data[:thumbnail_url].delete(item.thumbnail_url)
hanger = hangers_scope.find_or_initialize_by_item_id(item.id)
# If there's a hanger in the current list, we want it so we can update
# its quantity. If there's a hanger in another list, we want it so we
# know not to build a new one. Otherwise, build away!
existing_hangers = existing_hangers_by_item_id[item.id]
existing_hanger_in_current_list = existing_hangers.detect { |h|
h.list_id == current_list_id
}
hanger = existing_hanger_in_current_list || existing_hangers.first ||
hangers_scope.build
# We also don't want to move existing hangers from other lists, so only
# set the list if the hanger is new.
hanger.list = @closet_list if hanger.new_record?
# set the list if the hanger is new. (The item assignment is only
# necessary for new records, so may as well put it here, too.)
if hanger.new_record?
hanger.item = item
hanger.list = @closet_list
end
# Finally, we don't want to update the quantity of hangers in those other
# lists, either, so only update quantity if it's in this list. (This will
# be true for some existing hangers and all new hangers. This is also the
# only value that could change for existing hangers; if nothing changes,
# it was an existing hanger from another list.)
hanger.quantity = data[:quantity] if hanger.list == @closet_list
hanger.quantity = data[:quantity] if hanger.list_id == current_list_id
hanger
end