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Marcello Costagliola
ca626ea7e2
Every room visit and every reconnection asks for the messages updated since the page was rendered. That query filtered the room by updated_at and sorted it by created_at, so SQLite walked every message in the room: about 220-360 ms in a room of a million messages. An index on (room_id, updated_at) finds the few updated messages directly. Sorting on +created_at keeps SQLite on that index once messages are also indexed by (room_id, created_at): with both, the planner otherwise walks the room in creation order looking for updated rows. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01JVFo3Lt9T8M5NR7KxVvsZ2
59 lines
1.8 KiB
Ruby
59 lines
1.8 KiB
Ruby
module Message::Pagination
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extend ActiveSupport::Concern
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PAGE_SIZE = 40
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# Expose Rails' collection-preloading hook while preserving Array pagination and
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# validators. The renderer passes only cache misses to preload_associations.
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class Page < Array
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def self.load(relation, direction, size)
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new(relation.skip_preloading!.public_send(direction, size), relation)
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end
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def initialize(records, relation)
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super(records)
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@relation = relation
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end
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def loaded?
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true
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end
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def preload_associations(records)
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@relation.preload_associations(records)
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end
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end
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included do
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# Keep presentation data lazy until the collection cache knows which messages missed.
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scope :last_page, -> { last_page_of(PAGE_SIZE) }
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scope :first_page, -> { Page.load(ordered, :first, PAGE_SIZE) }
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scope :before, ->(message) { where("created_at < ?", message.created_at) }
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scope :after, ->(message) { where("created_at > ?", message.created_at) }
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scope :page_before, ->(message) { before(message).last_page }
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scope :page_after, ->(message) { after(message).first_page }
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scope :page_created_since, ->(time) { where("created_at > ?", time).first_page }
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# Sorting on +created_at, which no index covers, has SQLite find the few messages updated since
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# through (room_id, updated_at) and sort just those, instead of walking the whole room by
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# (room_id, created_at) looking for them.
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scope :page_updated_since, ->(time) { Page.load(where("updated_at > ?", time).reorder(Arel.sql("+messages.created_at")), :last, PAGE_SIZE) }
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end
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class_methods do
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def last_page_of(size)
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Page.load(ordered, :last, size)
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end
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def page_around(message)
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Page.new(page_before(message) + [ message ] + page_after(message), ordered)
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end
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def paged?
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count > PAGE_SIZE
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end
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end
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end
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