Class: DynamoidAdvancedWhere::QueryMaterializer

Inherits:
Object
  • Object
show all
Includes:
Enumerable
Defined in:
lib/dynamoid_advanced_where/query_materializer.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(query_builder:) ⇒ QueryMaterializer

Returns a new instance of QueryMaterializer.



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# File 'lib/dynamoid_advanced_where/query_materializer.rb', line 14

def initialize(query_builder:)
  self.query_builder = query_builder
end

Instance Attribute Details

#query_builder ⇒ Object

Returns the value of attribute query_builder.



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# File 'lib/dynamoid_advanced_where/query_materializer.rb', line 8

def query_builder
  @query_builder
end

Instance Method Details

#all ⇒ Object 



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# File 'lib/dynamoid_advanced_where/query_materializer.rb', line 18

def all
  each.to_a
end

#all_possible_indexes ⇒ Object 



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# File 'lib/dynamoid_advanced_where/query_materializer.rb', line 148

def all_possible_indexes
  # The nil index name is the table itself
  idx = { nil => { hash_key: klass.hash_key.to_s, range_key: klass.range_key.to_s } }

  klass.indexes.each do |_, definition|
    next unless definition.projected_attributes == :all

    idx[definition.name] = { hash_key: definition.hash_key.to_s, range_key: definition.range_key.to_s }
  end

  idx
end

#construct_items(items) ⇒ Object 



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# File 'lib/dynamoid_advanced_where/query_materializer.rb', line 74

def construct_items(items)
  (items || []).map do |item|
    klass.from_database(item)
  end
end

#each(&blk) ⇒ Object Also known as: find_each 



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# File 'lib/dynamoid_advanced_where/query_materializer.rb', line 22

def each(&blk)
  return enum_for(:each) unless blk

  records.each(&blk)
end

#each_page(&blk) ⇒ Object 



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# File 'lib/dynamoid_advanced_where/query_materializer.rb', line 29

def each_page(&blk)
  return enum_for(:each_page) unless blk

  pages.each(&blk)
end

#each_page_via_query ⇒ Object 



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# File 'lib/dynamoid_advanced_where/query_materializer.rb', line 80

def each_page_via_query
  query = {
    table_name: table_name,
    index_name: selected_index_for_query,
    scan_index_forward: query_builder.scanning_index_forward,
  }.merge(filter_builder.to_query_filter)

  enumerate_results(query) do |q|
    client.query(q)
  end
end

#each_page_via_scan ⇒ Object 



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# File 'lib/dynamoid_advanced_where/query_materializer.rb', line 92

def each_page_via_scan
  raise 'Unable to scan a table backwards' unless query_builder.scanning_index_forward

  query = {
    table_name: table_name,
  }.merge(filter_builder.to_scan_filter)

  enumerate_results(query) do |q|
    client.scan(q)
  end
end

#enumerate_results(starting_query) ⇒ Object 



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# File 'lib/dynamoid_advanced_where/query_materializer.rb', line 47

def enumerate_results(starting_query)
  query = starting_query.dup

  unless query_builder.projected_fields.empty?
    query[:select] = 'SPECIFIC_ATTRIBUTES'
    query[:projection_expression] = query_builder.projected_fields.map(&:to_s).join(',')
  end

  query[:limit] = query_builder.record_limit if query_builder.record_limit

  query[:exclusive_start_key] = start_hash

  Enumerator.new do |yielder|
    loop do
      results = yield(query)

      yielder.yield(construct_items(results.items), results)

      query[:limit] = query[:limit] - results.items.length if query[:limit]

      break if results.last_evaluated_key.nil? || query[:limit]&.zero?

      query[:exclusive_start_key] = results.last_evaluated_key
    end
  end.lazy
end

#filter_builder ⇒ Object 



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# File 'lib/dynamoid_advanced_where/query_materializer.rb', line 104

def filter_builder
  @filter_builder ||= FilterBuilder.new(
    root_node: query_builder.root_node,
    klass: klass,
  )
end

#must_scan? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/dynamoid_advanced_where/query_materializer.rb', line 135

def must_scan?
  satisfiable_indexes.empty?
end

#pages ⇒ Object 



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# File 'lib/dynamoid_advanced_where/query_materializer.rb', line 39

def pages
  if must_scan?
    each_page_via_scan
  else
    each_page_via_query
  end
end

#records ⇒ Object 



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# File 'lib/dynamoid_advanced_where/query_materializer.rb', line 35

def records
  pages.flat_map { |i, _| i }
end

#satisfiable_indexes ⇒ Object

find all indexes where we have a predicate on the hash key



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# File 'lib/dynamoid_advanced_where/query_materializer.rb', line 140

def satisfiable_indexes
  possible_fields = filter_builder.extractable_fields_for_hash_and_range

  all_possible_indexes.select do |_, definition|
    possible_fields.key?(definition[:hash_key])
  end
end

#selected_index_for_query ⇒ Object

Pick the index to query.

1) The first index chosen should be one that has the range and hash key satisfied.
2) The second should be one that has the hash key



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# File 'lib/dynamoid_advanced_where/query_materializer.rb', line 114

def selected_index_for_query
  possible_fields = filter_builder.extractable_fields_for_hash_and_range

  satisfiable_indexes.each do |name, definition|
    next unless possible_fields.key?(definition[:hash_key]) &&
                possible_fields.key?(definition[:range_key])

    filter_builder.select_node_for_range_key(possible_fields[definition[:range_key]])
    filter_builder.select_node_for_query_filter(possible_fields[definition[:hash_key]])

    return name
  end

  # Just take the first matching query then
  name, definition = satisfiable_indexes.first
  filter_builder.select_node_for_query_filter(possible_fields[definition[:hash_key]])
  filter_builder.select_node_for_range_key(possible_fields[definition[:range_key]]) unless possible_fields[definition[:range_key]].blank?

  name
end