Class: Sq::Dbsync::LoadAction

Inherits:
Object
  • Object
show all
Defined in:
lib/sq/dbsync/load_action.rb

Overview

An stateful action object representing the transfer of data from a source table to a target. The action can be performed in full using ‘#call`, but control can also be inverted using the `.stages` method, which allows the action to be combined to run efficiently in parallel with other actions.

This is useful because a single load taxes the source system then the target system in sequence, so for maximum efficency a second load should be interleaved to start taxing the source system as soon as the first finishes the extract, rather than waiting for it to also finish the load. This is not possible if the process is fully encapsulated as it is in ‘#call`.

This is an abstract base class, see ‘BatchLoadAction` and `IncrementalLoadAction` for example subclasses.

Defined Under Namespace

Classes: NullAction

Constant Summary collapse

EPOCH = 
Date.new(2000, 1, 1).to_time

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(target, plan, registry, logger, now = ->{ Time.now.utc }) ⇒ LoadAction

Returns a new instance of LoadAction.



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# File 'lib/sq/dbsync/load_action.rb', line 32

def initialize(target, plan, registry, logger, now = ->{ Time.now.utc })
  @target   = target
  @plan     = OpenStruct.new(plan)
  @registry = registry
  @logger   = logger
  @now      = now
end

Class Method Details

.stages ⇒ Object 



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# File 'lib/sq/dbsync/load_action.rb', line 48

def self.stages
  [
    ->(x) { x.do_prepare || NullAction.new },
    ->(x) { x.extract_data },
    ->(x) { x.load_data },
    ->(x) { x.post_load }
  ]
end

Instance Method Details

#call ⇒ Object 



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# File 'lib/sq/dbsync/load_action.rb', line 44

def call
  self.class.stages.inject(self) {|x, v| v.call(x) }
end

#do_prepare ⇒ Object 



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# File 'lib/sq/dbsync/load_action.rb', line 57

def do_prepare
  return unless prepare

  ensure_target_exists
  self
end

#tag ⇒ Object 



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# File 'lib/sq/dbsync/load_action.rb', line 40

def tag
  plan.table_name
end