Class: PgOnlineSchemaChange::Orchestrate

Inherits:
Object
  • Object
show all
Extended by:
Helper
Defined in:
lib/pg_online_schema_change/orchestrate.rb

Constant Summary collapse

SWAP_STATEMENT_TIMEOUT = 
"5s"
TRACK_PROGRESS_INTERVAL =

seconds

60

Class Method Summary collapse

Methods included from Helper

logger, method_missing, primary_key, respond_to_missing?

Class Method Details

.copy_data! ⇒ Object 



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# File 'lib/pg_online_schema_change/orchestrate.rb', line 204

def copy_data!
  # re-uses transaction with serializable
  # Begin the process to copy data into copy table
  # depending on the size of the table, this can be a time
  # taking operation.
  logger.info(
    "Clearing contents of audit table before copy..",
    { shadow_table: shadow_table, parent_table: client.table_name },
  )
  Query.run(client.connection, "DELETE FROM #{audit_table}", true)

  if client.copy_statement
    query = format(client.copy_statement, shadow_table: shadow_table)
    return Query.run(client.connection, query, true)
  end

  logger.info(
    "Copying contents..",
    { shadow_table: shadow_table, parent_table: client.table_name },
  )

  @copy_finished = false
  log_progress

  sql = Query.copy_data_statement(client, shadow_table, true)
  Query.run(client.connection, sql, true)
ensure
  Query.run(client.connection, "COMMIT;") # commit the serializable transaction
  @copy_finished = true
end

.drop_and_cleanup! ⇒ Object 



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# File 'lib/pg_online_schema_change/orchestrate.rb', line 339

def drop_and_cleanup!
  primary_drop = client.drop ? "DROP TABLE IF EXISTS #{old_primary_table};" : ""
  audit_table_drop = audit_table ? "DROP TABLE IF EXISTS #{audit_table}" : ""
  shadow_table_drop = shadow_table ? "DROP TABLE IF EXISTS #{shadow_table}" : ""

  sql = <<~SQL
    DROP TRIGGER IF EXISTS primary_to_audit_table_trigger ON #{client.table_name};
    #{audit_table_drop};
    #{shadow_table_drop};
    #{primary_drop}
    RESET statement_timeout;
    RESET client_min_messages;
    RESET lock_timeout;
  SQL

  Query.run(client.connection, sql)
end

.handle_signals! ⇒ Object 



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# File 'lib/pg_online_schema_change/orchestrate.rb', line 96

def handle_signals!
  reader = setup_signals!
  signal = reader.gets.chomp

  while !reader.closed? && reader.wait_readable # rubocop:disable Lint/UnreachableLoop
    logger.info("Signal #{signal} received, cleaning up")

    client.connection.cancel
    drop_and_cleanup!
    reader.close

    exit(Signal.list[signal])
  end
end

.log_progress ⇒ Object 



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# File 'lib/pg_online_schema_change/orchestrate.rb', line 235

def log_progress
  new_connection = client.checkout_connection
  source_table_size = Query.get_table_size(new_connection, client.schema, client.table_name)

  Thread.new do
    loop do
      break if @copy_finished

      shadow_table_size = Query.get_table_size(new_connection, client.schema, shadow_table)
      progress = (shadow_table_size.to_f / source_table_size) * 100
      logger.info("Estimated copy progress: #{progress.round(2)}% complete")

      break if @copy_finished || progress >= 100
      sleep(TRACK_PROGRESS_INTERVAL) unless ENV["CI"]
    rescue StandardError => e
      logger.info("Reporting progress failed: #{e.message}")
    end
  end
end

.replace_views! ⇒ Object 



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# File 'lib/pg_online_schema_change/orchestrate.rb', line 324

def replace_views!
  view_definitions = Query.view_definitions_for(client, old_primary_table)
  view_definitions.each do |definition|
    definition.each do |view_name, view_definition|
      view_definition = view_definition.gsub(old_primary_table, client.table)

      logger.info("Replacing view #{view_name}")
      sql = <<~SQL
        CREATE OR REPLACE VIEW #{view_name} AS #{view_definition}
      SQL
      Query.run(client.connection, sql)
    end
  end
end

.replay_and_swap! ⇒ Object 



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# File 'lib/pg_online_schema_change/orchestrate.rb', line 255

def replay_and_swap!
  Replay.begin!
rescue CountBelowDelta
  logger.info("Remaining rows below delta count, proceeding towards swap")

  swap!
end

.run!(options) ⇒ Object 



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# File 'lib/pg_online_schema_change/orchestrate.rb', line 56

def run!(options)
  setup!(options)
  Thread.new { handle_signals! }

  raise Error, "Parent table has no primary key, exiting..." if primary_key.nil?

  logger.info("Performing some house keeping....")
  run_analyze!
  run_vacuum!

  setup_audit_table!

  setup_trigger!
  setup_shadow_table! # re-uses transaction with serializable
  run_alter_statement! # re-uses transaction with serializable
  copy_data! # re-uses transaction with serializable
  run_analyze!
  replay_and_swap!
  run_analyze!
  validate_constraints!
  replace_views!
  drop_and_cleanup!

  logger.info("All tasks successfully completed")
rescue StandardError => e
  logger.fatal("Something went wrong: #{e.message}", { e: e })

  drop_and_cleanup!

  raise e
end

.run_alter_statement! ⇒ Object 



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# File 'lib/pg_online_schema_change/orchestrate.rb', line 191

def run_alter_statement!
  # re-uses transaction with serializable
  statement = Query.alter_statement_for(client, shadow_table)
  logger.info(
    "Running alter statement on shadow table",
    { shadow_table: shadow_table, parent_table: client.table_name },
  )
  Query.run(client.connection, statement, true)

  Store.set(:dropped_columns_list, Query.dropped_columns(client))
  Store.set(:renamed_columns_list, Query.renamed_columns(client))
end

.run_analyze! ⇒ Object 



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# File 'lib/pg_online_schema_change/orchestrate.rb', line 301

def run_analyze!
  logger.info("Performing ANALYZE!")

  client.connection.async_exec("ANALYZE VERBOSE \"#{client.schema}\".#{client.table_name};")
end

.run_vacuum! ⇒ Object 



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# File 'lib/pg_online_schema_change/orchestrate.rb', line 307

def run_vacuum!
  logger.info("Performing VACUUM!")

  client.connection.async_exec("VACUUM VERBOSE \"#{client.schema}\".#{client.table_name};")
end

.setup!(options) ⇒ Object 



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# File 'lib/pg_online_schema_change/orchestrate.rb', line 13

def setup!(options)
  client = Store.set(:client, Client.new(options))

  sql = <<~SQL
    SET statement_timeout = 0;
    SET client_min_messages = warning;
    SET search_path TO "#{client.schema}";
  SQL

  Query.run(client.connection, sql)
  # install functions
  Query.run(client.connection, FUNC_FIX_SERIAL_SEQUENCE)
  Query.run(client.connection, FUNC_CREATE_TABLE_ALL)

  setup_store
end

.setup_audit_table! ⇒ Object 



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# File 'lib/pg_online_schema_change/orchestrate.rb', line 111

def setup_audit_table!
  logger.info("Setting up audit table", { audit_table: audit_table })

  sql = <<~SQL
    CREATE TABLE #{audit_table} (#{audit_table_pk} SERIAL PRIMARY KEY, #{operation_type_column} text, #{trigger_time_column} timestamp, LIKE #{client.table_name}) WITH (autovacuum_enabled = false);
  SQL

  Query.run(client.connection, sql)

  Store.set(
    :audit_table_pk_sequence,
    Query.get_sequence_name(client, audit_table, audit_table_pk),
  )
end

.setup_shadow_table! ⇒ Object 



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# File 'lib/pg_online_schema_change/orchestrate.rb', line 166

def setup_shadow_table!
  logger.info("Setting up shadow table", { shadow_table: shadow_table })
  Query.run(
    client.connection,
    "SELECT create_table_all('#{client.table_name}', '#{shadow_table}');",
  )

  # re-uses transaction with serializable
  # This ensures that all queries from here till copy_data run with serializable.
  # This is to to ensure that once the trigger is added to the primay table
  # and contents being copied into the shadow, after a delete all on audit table,
  # any replaying of rows that happen next from audit table do not contain
  # any duplicates. We are ensuring there are no race conditions between
  # adding the trigger, till the copy ends, since they all happen in the
  # same serializable transaction.
  Query.run(client.connection, "SET TRANSACTION ISOLATION LEVEL SERIALIZABLE", true)

  # update serials
  Query.run(
    client.connection,
    "SELECT fix_serial_sequence('#{client.table_name}', '#{shadow_table}');",
    true,
  )
end

.setup_signals! ⇒ Object 



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# File 'lib/pg_online_schema_change/orchestrate.rb', line 88

def setup_signals!
  reader, writer = IO.pipe

  ['TERM', 'QUIT', 'INT'].each { |sig| trap(sig) { writer.puts sig } }

  reader
end

.setup_store ⇒ Object 



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# File 'lib/pg_online_schema_change/orchestrate.rb', line 30

def setup_store
  # Set this early on to ensure their creation and cleanup (unexpected)
  # happens at all times. IOW, the calls from Store.get always return
  # the same value.
  Store.set(:old_primary_table, "pgosc_op_table_#{client.table.downcase}")
  Store.set(:audit_table, "pgosc_at_#{client.table.downcase}_#{pgosc_identifier}")
  Store.set(:operation_type_column, "operation_type_#{pgosc_identifier}")
  Store.set(:trigger_time_column, "trigger_time_#{pgosc_identifier}")
  Store.set(:audit_table_pk, "at_#{pgosc_identifier}_id")
  Store.set(:shadow_table, "pgosc_st_#{client.table.downcase}_#{pgosc_identifier}")
  Store.set(
    :primary_table_storage_parameters,
    Query.storage_parameters_for(client, client.table_name, true) || "",
  )

  Store.set(
    :referential_foreign_key_statements,
    Query.referential_foreign_keys_to_refresh(client, client.table_name),
  )
  Store.set(
    :self_foreign_key_statements,
    Query.self_foreign_keys_to_refresh(client, client.table_name),
  )
  Store.set(:trigger_statements, Query.get_triggers_for(client, client.table_name))
end

.setup_trigger! ⇒ Object 



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# File 'lib/pg_online_schema_change/orchestrate.rb', line 126

def setup_trigger!
  # acquire access exclusive lock to ensure audit triggers
  # are setup fine. This also calls kill_backends (if opted in via flag)
  # so any competing backends will be killed to setup the trigger
  opened = Query.open_lock_exclusive(client, client.table_name)

  raise AccessExclusiveLockNotAcquired unless opened

  logger.info("Setting up triggers")

  sql = <<~SQL
    DROP TRIGGER IF EXISTS primary_to_audit_table_trigger ON #{client.table_name};

    CREATE OR REPLACE FUNCTION primary_to_audit_table_trigger()
    RETURNS TRIGGER AS
    $$
    BEGIN
      IF ( TG_OP = 'INSERT') THEN
        INSERT INTO "#{audit_table}" select nextval('#{audit_table_pk_sequence}'), 'INSERT', clock_timestamp(), NEW.* ;
        RETURN NEW;
      ELSIF ( TG_OP = 'UPDATE') THEN
        INSERT INTO "#{audit_table}" select nextval('#{audit_table_pk_sequence}'), 'UPDATE', clock_timestamp(),  NEW.* ;
        RETURN NEW;
      ELSIF ( TG_OP = 'DELETE') THEN
        INSERT INTO "#{audit_table}" select nextval('#{audit_table_pk_sequence}'), 'DELETE', clock_timestamp(), OLD.* ;
        RETURN NEW;
      END IF;
    END;
    $$ LANGUAGE PLPGSQL SECURITY DEFINER;

    CREATE TRIGGER primary_to_audit_table_trigger
    AFTER INSERT OR UPDATE OR DELETE ON #{client.table_name}
    FOR EACH ROW EXECUTE PROCEDURE primary_to_audit_table_trigger();
  SQL

  Query.run(client.connection, sql, opened)
ensure
  Query.run(client.connection, "COMMIT;")
end

.swap! ⇒ Object 



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# File 'lib/pg_online_schema_change/orchestrate.rb', line 263

def swap!
  logger.info("Performing swap!")
  # From here on, all statements are carried out in a single
  # transaction with access exclusive lock

  opened = Query.open_lock_exclusive(client, client.table_name)

  raise AccessExclusiveLockNotAcquired unless opened

  Query.run(
    client.connection,
    "SET statement_timeout to '#{SWAP_STATEMENT_TIMEOUT}';",
    opened,
  )

  rows = Replay.rows_to_play(opened)
  Replay.play!(rows, opened)

  query_for_primary_key_refresh =
    Query.query_for_primary_key_refresh(shadow_table, primary_key, client.table_name, opened)

  sql = <<~SQL
    #{query_for_primary_key_refresh};
    ALTER TABLE #{client.table_name} RENAME to #{old_primary_table};
    ALTER TABLE #{shadow_table} RENAME to #{client.table_name};
    #{referential_foreign_key_statements}
    #{self_foreign_key_statements}
    #{trigger_statements}
    #{storage_params_reset}
    DROP TRIGGER IF EXISTS primary_to_audit_table_trigger ON #{client.table_name};
  SQL

  Query.run(client.connection, sql, opened)
ensure
  Query.run(client.connection, "COMMIT;")
  Query.run(client.connection, "SET statement_timeout = 0;")
end

.validate_constraints! ⇒ Object 



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# File 'lib/pg_online_schema_change/orchestrate.rb', line 313

def validate_constraints!
  return if client.skip_foreign_key_validation

  Query
    .get_foreign_keys_to_validate(client, client.table_name)
    .each do |statement|
      logger.info("Validating constraints!", statement: statement)
      Query.run(client.connection, statement)
    end
end