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"

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 196

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 })
  Query.run(client.connection, "DELETE FROM #{audit_table}", true)

  logger.info("Copying contents..", { shadow_table: shadow_table, parent_table: client.table })
  if client.copy_statement
    query = format(client.copy_statement, shadow_table: shadow_table)
    return Query.run(client.connection, query, true)
  end

  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
end

.disable_vacuum!Object


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# File 'lib/pg_online_schema_change/orchestrate.rb', line 165

def disable_vacuum!
  # re-uses transaction with serializable
  # Disabling vacuum to avoid any issues during the process
  result = Query.storage_parameters_for(client, client.table, true) || ""
  Store.set(:primary_table_storage_parameters, result)

  logger.debug("Disabling vacuum on shadow and audit table",
               { shadow_table: shadow_table, audit_table: audit_table })
  sql = <<~SQL
    ALTER TABLE #{shadow_table} SET (
      autovacuum_enabled = false, toast.autovacuum_enabled = false
    );

    ALTER TABLE #{audit_table} SET (
      autovacuum_enabled = false, toast.autovacuum_enabled = false
    );
  SQL
  Query.run(client.connection, sql, true)
end

.drop_and_cleanup!Object


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# File 'lib/pg_online_schema_change/orchestrate.rb', line 270

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};
    #{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 82

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

  while !reader.closed? && IO.select([reader]) # 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

.replay_and_swap!Object


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# File 'lib/pg_online_schema_change/orchestrate.rb', line 216

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 45

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

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

  setup_audit_table!
  setup_trigger!
  setup_shadow_table! # re-uses transaction with serializable
  disable_vacuum! # 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!
  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 185

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 })
  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 256

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

  Query.run(client.connection, "ANALYZE VERBOSE #{client.table};")
end

.setup!(options) ⇒ Object


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# File 'lib/pg_online_schema_change/orchestrate.rb', line 12

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 97

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});
  SQL

  Query.run(client.connection, sql)
end

.setup_shadow_table!Object


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# File 'lib/pg_online_schema_change/orchestrate.rb', line 147

def setup_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)
  logger.info("Setting up shadow table", { shadow_table: shadow_table })

  Query.run(client.connection, "SELECT create_table_all('#{client.table}', '#{shadow_table}');", true)

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

.setup_signals!Object


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# File 'lib/pg_online_schema_change/orchestrate.rb', line 72

def setup_signals!
  reader, writer = IO.pipe

  %w[TERM QUIT INT].each do |sig|
    trap(sig) { writer.puts sig }
  end

  reader
end

.setup_storeObject


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# File 'lib/pg_online_schema_change/orchestrate.rb', line 29

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}")
  Store.set(:audit_table, "pgosc_at_#{client.table}_#{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(:audit_table_pk_sequence, "#{audit_table}_#{audit_table_pk}_seq")
  Store.set(:shadow_table, "pgosc_st_#{client.table}_#{pgosc_identifier}")

  Store.set(:referential_foreign_key_statements, Query.referential_foreign_keys_to_refresh(client, client.table))
  Store.set(:self_foreign_key_statements, Query.self_foreign_keys_to_refresh(client, client.table))
end

.setup_trigger!Object


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# File 'lib/pg_online_schema_change/orchestrate.rb', line 107

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)

  raise AccessExclusiveLockNotAcquired unless opened

  logger.info("Setting up triggers")

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

    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}
    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 224

def swap!
  logger.info("Performing swap!")

  storage_params_reset = primary_table_storage_parameters.empty? ? "" : "ALTER TABLE #{client.table} SET (#{primary_table_storage_parameters});"

  # From here on, all statements are carried out in a single
  # transaction with access exclusive lock

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

  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)

  sql = <<~SQL
    ALTER TABLE #{client.table} RENAME to #{old_primary_table};
    ALTER TABLE #{shadow_table} RENAME to #{client.table};
    #{referential_foreign_key_statements}
    #{self_foreign_key_statements}
    #{storage_params_reset}
    DROP TRIGGER IF EXISTS primary_to_audit_table_trigger ON #{client.table};
  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 262

def validate_constraints!
  logger.info("Validating constraints!")

  validate_statements = Query.get_foreign_keys_to_validate(client, client.table)

  Query.run(client.connection, validate_statements)
end