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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.
29 lines
855 B
Ruby
29 lines
855 B
Ruby
# frozen_string_literal: true
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class CopyNotificationsIdValues < ActiveRecord::Migration[7.0]
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disable_ddl_transaction!
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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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min_id, max_id = execute("SELECT MIN(id), MAX(id) FROM notifications")[0].values
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batch_size = 10_000
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(min_id..max_id).step(batch_size) { |start_id| execute <<~SQL } if min_id && max_id
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UPDATE notifications
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SET new_id = id
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WHERE id >= #{start_id} AND id < #{start_id + batch_size} AND new_id != id
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SQL
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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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