Module: ROM::Plugins::Relation::SQL::Postgres::Streaming

Defined in:
lib/rom/plugins/relation/sql/postgres/streaming.rb

Overview

PG-specific extensions which adds Relation#stream method

Defined Under Namespace

Modules: Combined, Composite Classes: StreamingNotSupportedError

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.apply(target, **_opts) ⇒ Object 



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# File 'lib/rom/plugins/relation/sql/postgres/streaming.rb', line 16

def self.apply(target, **_opts)
  conn = registry.gateways[target.config.component.gateway].connection

  return unless conn.database_type.to_sym == :postgres

  return if defined?(JRUBY_VERSION)

  begin
    require "sequel_pg"
  rescue LoadError
    raise StreamingNotSupportedError, "add sequel_pg to Gemfile to use pg_streaming"
  end

  unless Sequel::Postgres.supports_streaming?
    raise StreamingNotSupportedError, "postgres version does not support streaming"
  end

  conn.extension(:pg_streaming)

  target.include(Streaming)
end

.included(klass) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future. 



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# File 'lib/rom/plugins/relation/sql/postgres/streaming.rb', line 39

def self.included(klass)
  super
  ROM::Relation::Graph.include(Combined)
  ROM::Relation::Composite.include(Composite)
end

Instance Method Details

#stream_each ⇒ Relation

Allows you to stream returned rows one at a time, instead of collecting the entire result set in memory. Requires the sequel_pg gem

Examples:

posts.stream_each { |post| puts CSV.generate_line(post) }

Returns:

See Also:



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# File 'lib/rom/plugins/relation/sql/postgres/streaming.rb', line 57

def stream_each
  raise StreamingNotSupportedError, "not supported on jruby"
end