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 = 
"3.0"

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 145

def self.bump(connection, *channels)
	channels = [channels].flatten.sort
	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 113

def self.bump_sql(*channels)
	channels = [channels].flatten.sort
	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 95

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 104

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 160

def self.read(connection, *channels)
	PgVersions.with_connection(connection, false) { |pg_connection|
		channels = [channels].flatten.sort
		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 90

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, 'YYYYMMDD')::integer || ',' || to_char(%s, 'HH24MISS')::integer || ',' || to_char(%s, '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