55 lines
1.9 KiB
Ruby
55 lines
1.9 KiB
Ruby
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# frozen_string_literal: true
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require 'securerandom'
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# This migration changes the IDs of several tables from serial to a
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# timestamped/"snowflake" one.
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#
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# Instead of "snowflakes" we shall call those IDs Cornflakes or Waspflakes
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# instead.
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#
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# Implementation somewhat lifted from Mastodon.
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class UseTimestampedIds < ActiveRecord::Migration[5.2]
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def up
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# PL/pgSQL is just spicy pascal
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# don't @ me
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execute <<~SQL
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CREATE or replace FUNCTION gen_timestamp_id(tblname text) RETURNS bigint AS $$
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DECLARE
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timepart bigint;
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seqpart bigint;
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BEGIN
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timepart := (date_part('epoch', now()) * 1000)::bigint << 16;
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seqpart := ('x' || substr(md5(tblname ||
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'#{SecureRandom.hex(16)}' ||
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timepart::text), 1, 4))::bit(16)::bigint;
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RETURN timepart | ((seqpart + nextval(tblname || '_id_seq')) & 65535);
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END;
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$$ LANGUAGE plpgsql VOLATILE;
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SQL
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# we need to migrate related columns to bigints for this to work
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{
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question: %i[answers inboxes],
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answer: %i[comments smiles subscriptions],
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comment: %i[comment_smiles],
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user: %i[announcements answers comment_smiles comments inboxes list_members lists moderation_comments moderation_votes questions reports services smiles subscriptions themes users_roles],
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# polymorphic tables go brrr
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recipient: %i[notifications],
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source: %i[relationships],
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target: %i[notifications relationships reports],
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}.each do |ref, tbls|
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tbls.each do |tbl|
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say "Migrating #{tbl}.#{ref}_id to bigint"
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change_column(tbl, :"#{ref}_id", :bigint)
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end
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end
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%i[questions answers comments smiles comment_smiles users].each do |tbl|
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say "Migrating #{tbl} to use timestamped ids"
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change_column(tbl, :id, :bigint, default: -> { "gen_timestamp_id('#{tbl}'::text)" })
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end
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end
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end
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