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The `notifications.id` column is the most probable column to run out of values. This is because it is an `int` column that has only 2147483647 values and many notifications are generated on a regular basis in an active community. This commit migrates the column to `bigint`. These migrations do not use `ALTER TABLE ... COLUMN ... TYPE` in order to avoid the `ACCESS EXCLUSIVE` lock on the entire table. Instead, they create a new `bigint` column, copy the values to the new column and then sets the new column as primary key. Related columns (see `user_badges`, `shelved_notifications`) will be migrated in a follow-up commit.
44 lines
1.6 KiB
Ruby
44 lines
1.6 KiB
Ruby
# frozen_string_literal: true
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class SwapBigIntNotificationsId < ActiveRecord::Migration[7.0]
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def up
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# Short-circuit if the table has been migrated already
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result =
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execute(
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"SELECT data_type FROM information_schema.columns WHERE table_name = 'notifications' AND column_name = 'id' LIMIT 1",
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)
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data_type = result[0]["data_type"]
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return if data_type.downcase == "bigint"
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# Necessary to rename and drop columns
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Migration::SafeMigrate.disable!
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# Drop trigger and function used to replicate new values
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execute "DROP TRIGGER notifications_new_id_trigger ON notifications"
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execute "DROP FUNCTION mirror_notifications_id()"
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# Move sequence to new column
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execute "ALTER TABLE notifications ALTER COLUMN id DROP DEFAULT"
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execute "ALTER TABLE notifications ALTER COLUMN new_id SET DEFAULT nextval('notifications_id_seq'::regclass)"
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execute "ALTER SEQUENCE notifications_id_seq OWNED BY notifications.new_id"
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# Swap columns
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execute "ALTER TABLE notifications RENAME COLUMN id TO old_id"
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execute "ALTER TABLE notifications RENAME COLUMN new_id TO id"
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# Recreate primary key
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execute "ALTER TABLE notifications DROP CONSTRAINT notifications_pkey"
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execute "ALTER TABLE notifications ADD CONSTRAINT notifications_pkey PRIMARY KEY USING INDEX notifications_pkey_bigint"
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# Keep old column and mark it as read only
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execute "ALTER TABLE notifications ALTER COLUMN old_id DROP NOT NULL"
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Migration::ColumnDropper.mark_readonly(:notifications, :old_id)
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ensure
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Migration::SafeMigrate.enable!
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end
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def down
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raise ActiveRecord::IrreversibleMigration
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end
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end
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