Module: PgVersions

Defined in:
lib/pg_versions/pg_versions.rb,
lib/pg_versions.rb,
lib/pg_versions/rails.rb,
lib/pg_versions/version.rb

Overview

TODO: prepared statements? TODO: use ractor instead of thread for event listening

Defined Under Namespace

Classes: Connection, ConnectionClosed, ConnectionInner, Engine, InvalidParameters, Notification

Constant Summary collapse

VERSION = 
"3.3"

Class Method Summary collapse

Class Method Details

.bump(connection, *channels) ⇒ Object

TODO: ensure this is called only once per transaction, or that all bumps occur in the same order in all transactions, to avoid deadlocks



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# File 'lib/pg_versions/pg_versions.rb', line 147

def self.bump(connection, *channels)
  channels = [channels].flatten.sort.uniq
  PgVersions.with_connection(connection, false) { |pg_connection|
    sql = self.bump_sql(*channels)
    return {} if sql == ""
    pg_connection.exec(sql) { |result|
      result.map { |row| [channels[Integer(row["i"])], string_to_version(row["version"])] }.to_h
    }
  }
end

.bump_sql(*channels) ⇒ Object 



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# File 'lib/pg_versions/pg_versions.rb', line 115

def self.bump_sql(*channels)
  channels = [channels].flatten
  return ""  if channels.size == 0
  encoder = PG::TextEncoder::QuotedLiteral.new(elements_type: PG::TextEncoder::String.new)
  quoted_channels = channels.map.with_index { |channel, i| "(#{i},#{encoder.encode(channel)})" }.join(", ")
  # table-wide share lock is there to mutually exclude table cleaner
  # clock_timestamp() - this has to be a timestamp after table lock got acquired
  "
    LOCK TABLE pg_versions IN ACCESS SHARE MODE;
    WITH
      to_bump(i, channel) AS (VALUES #{quoted_channels})
      , current_instant(ts) AS (VALUES (clock_timestamp()))
      , updated AS (
          INSERT INTO pg_versions(channel, instant, counter)
          SELECT to_bump.channel, (SELECT ts FROM current_instant), 0 FROM to_bump
          ON CONFLICT (channel) DO UPDATE SET
            instant = GREATEST(pg_versions.instant, EXCLUDED.instant),
            counter = CASE WHEN pg_versions.instant < EXCLUDED.instant THEN 0 ELSE pg_versions.counter + 1 END
          RETURNING channel, instant, pg_versions.counter
          )
    SELECT DISTINCT
      i
      , #{timestamp_to_integers('updated.instant')} || ',' || updated.counter::text AS version
      , pg_notify(updated.channel::text, #{timestamp_to_integers('updated.instant')} || ',' || updated.counter::text)::text
    FROM
      to_bump
      JOIN updated ON to_bump.channel = updated.channel;
  "
end

.create_table(connection) ⇒ Object 



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# File 'lib/pg_versions/pg_versions.rb', line 97

def self.create_table(connection)
  PgVersions.with_connection(connection, false) { |pg_connection|
    open(File.dirname(__FILE__)+"/../../create-table.sql") { |sql_file|
      pg_connection.exec sql_file.read
    }
  }
end

.drop_table(connection) ⇒ Object 



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# File 'lib/pg_versions/pg_versions.rb', line 106

def self.drop_table(connection)
  PgVersions.with_connection(connection, false) { |pg_connection|
    open(File.dirname(__FILE__)+"/../../drop-table.sql") { |sql_file|
      pg_connection.exec sql_file.read
    }
  }
end

.read(connection, *channels) ⇒ Object

TODO: bump in the same query instead of calling bump TODO: do we really need to bump though? TODO: and then, implement read_sql



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# File 'lib/pg_versions/pg_versions.rb', line 162

def self.read(connection, *channels)
  PgVersions.with_connection(connection, false) { |pg_connection|
    channels = [channels].flatten.sort.uniq
    return {} if channels.size == 0
    versions = {}
    quoted_channels = channels.map.with_index { |channel, i| "(#{i},'#{pg_connection.escape_string(channel)}')" }.join(", ")
    not_found_channels = pg_connection.exec("
      LOCK TABLE pg_versions IN ACCESS SHARE MODE;
      WITH
        channels(i, channel) AS (VALUES #{quoted_channels})
      SELECT
        i
        , #{timestamp_to_integers('instant')} || ',' || counter AS version
      FROM
        channels
        JOIN pg_versions ON pg_versions.channel = channels.channel
      ORDER BY
        i DESC;
    ") { |result|
      result.each { |row|
        versions[channels.delete_at(Integer(row["i"]))] = string_to_version(row["version"])
      }
    }
    versions.merge!(self.bump(pg_connection, channels))  if channels.size > 0
    versions
  }
end

.string_to_version(version_str) ⇒ Object 



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# File 'lib/pg_versions/pg_versions.rb', line 92

def self.string_to_version(version_str)
  version_str.split(",").map { |str| Integer(str) }
end

.timestamp_to_integers(input) ⇒ Object 



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# File 'lib/pg_versions/pg_versions.rb', line 40

def self.timestamp_to_integers(input)
  "to_char(%s AT TIME ZONE 'UTC', 'YYYYMMDD')::integer || ',' || to_char(%s AT TIME ZONE 'UTC', 'HH24MISS')::integer || ',' || to_char(%s AT TIME ZONE 'UTC', 'US')::integer"%[input, input, input]
end

.with_connection(pg_connection_param, reset, &block) ⇒ Object 



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# File 'lib/pg_versions/pg_versions.rb', line 45

def self.with_connection(pg_connection_param, reset, &block)
  if pg_connection_param.kind_of? ::PG::Connection
    if reset
      pg_connection_param.sync_reset
      pg_connection_param.exec("select;")
    end
    block.call(pg_connection_param)
  elsif pg_connection_param.respond_to? :call
    pg_connection_param.call(reset, &block)
  elsif pg_connection_param.kind_of?(String) or pg_connection_param.kind_of?(Hash)
    Thread.handle_interrupt(Object => :never) {
      begin
        pg_connection = nil
        Thread.handle_interrupt(Object => :immediate) {
          pg_connection = ::PG.connect(pg_connection_param)
          block.call(pg_connection)
        }
      ensure
        pg_connection&.close
      end
    }
  elsif defined?(ActiveRecord) and pg_connection_param.kind_of?(Class) and pg_connection_param <= ActiveRecord::Base
    pg_connection = pg_connection_param.connection.raw_connection
    if reset
      pg_connection.sync_reset
      pg_connection.exec("select;")
    end
    block.call(pg_connection)
  else
    raise InvalidParameters, "Invalid connection parameter (#{pg_connection_param.inspect}). Either pass PG::Connection object, url string, hash, ActiveRecord::Base class (or subclass) or call one of the ActiveRecord methods that come with PgVersions refinement."
  end
end