Class: ElasticGraph::GraphQL::Resolvers::QueryAdapter

Inherits:
Object
  • Object
show all
Defined in:
lib/elastic_graph/graphql/resolvers/query_adapter.rb

Overview

Responsible for taking raw GraphQL query arguments and transforming them into a DatastoreQuery object.

Instance Method Summary collapse

Constructor Details

#initialize(datastore_query_builder:, datastore_query_adapters:) ⇒ QueryAdapter

Returns a new instance of QueryAdapter.



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# File 'lib/elastic_graph/graphql/resolvers/query_adapter.rb', line 15

def initialize(datastore_query_builder:, datastore_query_adapters:)
  @datastore_query_builder = datastore_query_builder
  @datastore_query_adapters = datastore_query_adapters
end

Instance Method Details

#build_query_from(field:, args:, lookahead:, context: {}) ⇒ Object 



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# File 'lib/elastic_graph/graphql/resolvers/query_adapter.rb', line 20

def build_query_from(field:, args:, lookahead:, context: {})
  monotonic_clock_deadline = context[:monotonic_clock_deadline]

  # Building an `DatastoreQuery` is not cheap; we do a lot of work to:
  #
  # 1) Convert the `args` to their schema form.
  # 2) Reduce over our different query builders into a final `Query` object
  # 3) ...and those individual query builders often do a lot of work (traversing lookaheads, etc).
  #
  # So it is beneficial to avoid re-creating the exact same `DatastoreQuery` object when
  # we are resolving the same field in the context of a different object. For example,
  # consider a query like:
  #
  # query {
  #   widgets {
  #     components {
  #       id
  #       parts {
  #         id
  #       }
  #     }
  #   }
  # }
  #
  # Here `components` and `parts` are nested relation fields. If we load 50 of each collection,
  # this `build_query_from` method will be called 50 times for the `Widget.components` field,
  # and 2500 times (50 * 50) for the `Component.parts` field...but for a given field, the
  # built `DatastoreQuery` will be exactly the same.
  #
  # Therefore, it is beneficial to memoize the `DatastoreQuery` to avoid re-doing the same work
  # over and over again, provided we can do so safely.
  #
  # `context` is a hash-like `GraphQL::Query::Context` object. Each executed query gets its own
  # instance, so we can safely cache things in it and trust that it will not "leak" to another
  # query execution. We carefully build a cache key below to ensure that we only ever reuse
  # the same `DatastoreQuery` in a situation that would produce the exact same `DatastoreQuery`.
  context[:datastore_query_cache] ||= {}
  context[:datastore_query_cache][cache_key_for(field, args, lookahead)] ||=
    build_new_query_from(field, args, lookahead, context, monotonic_clock_deadline)
end