Class: ConceptQL::Nodes::First

Inherits:
Occurrence show all
Defined in:
lib/conceptql/nodes/first.rb

Overview

Represents a node that will grab the first occurrence of something

The node treats all streams as a single, large stream. It partitions that larget stream by person_id, then sorts within those groupings by start_date and then select at most one row per person, regardless of how many different types of streams enter the node

If two rows have the same start_date, the order of their ranking is arbitrary

If we ask for the first occurrence of something and a person has no occurrences, this node returns nothing for that person

Constant Summary

Constants inherited from Node

Node::KNOWN_TYPES

Instance Attribute Summary

Attributes inherited from Node

#values

Instance Method Summary collapse

Methods inherited from Occurrence

#query

Methods inherited from Node

#arguments, #children, #columns, #date_columns, #evaluate, #initialize, #select_it, #stream, #types

Constructor Details

This class inherits a constructor from ConceptQL::Nodes::Node

Instance Method Details

#occurrence ⇒ Object 



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# File 'lib/conceptql/nodes/first.rb', line 18

def occurrence
  1
end