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33 lines
1.1 KiB
33 lines
1.1 KiB
7 years ago
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class StatusIdsToTimestampIds < ActiveRecord::Migration[5.1]
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def up
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# Prepare the function we will use to generate IDs.
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Rake::Task['db:define_timestamp_id'].execute
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# Set up the statuses.id column to use our timestamp-based IDs.
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ActiveRecord::Base.connection.execute(<<~SQL)
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ALTER TABLE statuses
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ALTER COLUMN id
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SET DEFAULT timestamp_id('statuses')
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SQL
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# Make sure we have a sequence to use.
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Rake::Task['db:ensure_id_sequences_exist'].execute
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end
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def down
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# Revert the column to the old method of just using the sequence
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# value for new IDs. Set the current ID sequence to the maximum
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# existing ID, such that the next sequence will be one higher.
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# We lock the table during this so that the ID won't get clobbered,
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# but ID is indexed, so this should be a fast operation.
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ActiveRecord::Base.connection.execute(<<~SQL)
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LOCK statuses;
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SELECT setval('statuses_id_seq', (SELECT MAX(id) FROM statuses));
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ALTER TABLE statuses
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ALTER COLUMN id
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SET DEFAULT nextval('statuses_id_seq');"
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SQL
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end
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end
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