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