Add primary key to preview_cards_statuses join table (includes deduplication migration) (#25243)
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5 changed files with 93 additions and 5 deletions
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# frozen_string_literal: true |
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class AddUniqueIndexOnPreviewCardsStatuses < ActiveRecord::Migration[6.1] |
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disable_ddl_transaction! |
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def up |
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add_index :preview_cards_statuses, [:status_id, :preview_card_id], name: :preview_cards_statuses_pkey, algorithm: :concurrently, unique: true |
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rescue ActiveRecord::RecordNotUnique |
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deduplicate_and_reindex! |
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end |
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def down |
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remove_index :preview_cards_statuses, name: :preview_cards_statuses_pkey |
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end |
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private |
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def deduplicate_and_reindex! |
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deduplicate_preview_cards! |
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safety_assured { execute 'REINDEX INDEX preview_cards_statuses_pkey' } |
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rescue ActiveRecord::RecordNotUnique |
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retry |
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end |
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def deduplicate_preview_cards! |
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# Statuses should have only one preview card at most, even if that's not the database |
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# constraint we will end up with |
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duplicate_ids = select_all('SELECT status_id FROM preview_cards_statuses GROUP BY status_id HAVING count(*) > 1;').rows |
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duplicate_ids.each_slice(1000) do |ids| |
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# This one is tricky: since we don't have primary keys to keep only one record, |
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# use the physical `ctid` |
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safety_assured do |
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execute "DELETE FROM preview_cards_statuses p WHERE p.status_id IN (#{ids.join(', ')}) AND p.ctid NOT IN (SELECT q.ctid FROM preview_cards_statuses q WHERE q.status_id = p.status_id LIMIT 1)" |
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end |
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end |
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end |
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end |
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# frozen_string_literal: true |
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class AddPrimaryKeyToPreviewCardsStatusesJoinTable < ActiveRecord::Migration[6.1] |
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disable_ddl_transaction! |
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def up |
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safety_assured do |
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execute 'ALTER TABLE preview_cards_statuses ADD PRIMARY KEY USING INDEX preview_cards_statuses_pkey' |
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end |
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end |
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def down |
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safety_assured do |
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# I have found no way to demote the primary key to an index, instead, re-create the index |
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execute 'CREATE UNIQUE INDEX CONCURRENTLY preview_cards_statuses_pkey_tmp ON preview_cards_statuses (status_id, preview_card_id)' |
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execute 'ALTER TABLE preview_cards_statuses DROP CONSTRAINT preview_cards_statuses_pkey' |
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execute 'ALTER INDEX preview_cards_statuses_pkey_tmp RENAME TO preview_cards_statuses_pkey' |
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end |
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end |
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end |
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