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class CopyAccountStats < ActiveRecord::Migration[5.2]
disable_ddl_transaction!
def up
safety_assured do
if supports_upsert?
up_fast
else
up_slow
end
end
end
def down
# Nothing
end
private
def supports_upsert?
version = select_one("SELECT current_setting('server_version_num') AS v")['v'].to_i
version >= 90_500
end
def up_fast
say 'Upsert is available, importing counters using the fast method'
Account.unscoped.select('id').find_in_batches(batch_size: 5_000) do |accounts|
execute <<-SQL.squish
INSERT INTO account_stats (account_id, statuses_count, following_count, followers_count, created_at, updated_at)
SELECT id, statuses_count, following_count, followers_count, created_at, updated_at
FROM accounts
WHERE id IN (#{accounts.map(&:id).join(', ')})
ON CONFLICT (account_id) DO UPDATE
SET statuses_count = EXCLUDED.statuses_count, following_count = EXCLUDED.following_count, followers_count = EXCLUDED.followers_count
SQL
end
end
def up_slow
say 'Upsert is not available in PostgreSQL below 9.5, falling back to slow import of counters'
# We cannot use bulk INSERT or overarching transactions here because of possible
# uniqueness violations that we need to skip over
Account.unscoped.select('id, statuses_count, following_count, followers_count, created_at, updated_at').find_each do |account|
params = [[nil, account.id], [nil, account[:statuses_count]], [nil, account[:following_count]], [nil, account[:followers_count]], [nil, account.created_at], [nil, account.updated_at]]
exec_insert('INSERT INTO account_stats (account_id, statuses_count, following_count, followers_count, created_at, updated_at) VALUES ($1, $2, $3, $4, $5, $6)', nil, params)
rescue ActiveRecord::RecordNotUnique
next
end
end
end
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