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Contents
# frozen_string_literal: true
module Praxis
module Extensions
module FieldSelection
class ActiveRecordQuerySelector
attr_reader :selector, :query
# Gets a dataset, a selector...and should return a dataset with the selector definition applied.
def initialize(query:, selectors:, debug: false)
@selector = selectors
@query = query
@logger = debug ? Logger.new($stdout) : nil
end
def generate
# TODO: unfortunately, I think we can only control the select clauses for the top model
# (as I'm not sure ActiveRecord supports expressing it in the join...)
@query = add_select(query: query, selector_node: selector)
eager_hash = _eager(selector)
@query = @query.includes(eager_hash)
explain_query(query, eager_hash) if @logger
@query
end
def add_select(query:, selector_node:)
# We're gonna always require the PK of the model, as it is a special case for AR, and the app itself
# might assume it is always there and not be surprised by the fact that if it isn't, it won't blow up
# in the same way as any other attribute not being loaded...i.e., ActiveModel::MissingAttributeError: missing attribute: xyz
select_fields = selector_node.select + [selector_node.resource.model.primary_key.to_sym]
select_fields.empty? ? query : query.select(*select_fields)
end
def _eager(selector_node)
selector_node.tracks.transform_values do |track_node|
_eager(track_node)
end
end
def explain_query(query, eager_hash)
@logger.debug("Query plan for ...#{selector.resource.model} with selectors: #{JSON.generate(selector.dump)}")
@logger.debug(" ActiveRecord query: #{selector.resource.model}.includes(#{eager_hash})")
query.explain
@logger.debug('Query plan end')
end
end
end
end
end
Version data entries
17 entries across 17 versions & 1 rubygems