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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
32 lines
1.2 KiB
Ruby
32 lines
1.2 KiB
Ruby
require "test_helper"
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class Message::PaginationTest < ActiveSupport::TestCase
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test "messages updated since a time are found through the room and update time index" do
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assert_match(/USING INDEX index_messages_on_room_id_and_updated_at \(room_id=\? AND updated_at>\?\)/, plan_of_page_updated_since)
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end
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test "messages updated since a time are the newest page of them, in creation order" do
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room = rooms(:watercooler)
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first, second, third = room.messages.ordered.first(3)
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travel 1.minute do
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[ third, first, second ].each(&:touch)
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stub_const(Message::Pagination, :PAGE_SIZE, 2) do
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assert_equal [ second, third ], room.messages.page_updated_since(30.seconds.ago).to_a
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end
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end
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end
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private
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def plan_of_page_updated_since
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statements = []
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callback = ->(*, payload) { statements << payload[:sql] if payload[:sql].start_with?(%(SELECT "messages")) }
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ActiveSupport::Notifications.subscribed(callback, "sql.active_record") do
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rooms(:watercooler).messages.page_updated_since(1.minute.ago)
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end
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Message.connection.select_rows("EXPLAIN QUERY PLAN #{statements.sole}").map(&:last).join(" | ")
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end
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end
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