Module: CompositePrimaryKeys::Predicates

Extended by:
Predicates
Included in:
Predicates
Defined in:
lib/composite_primary_keys/composite_predicates.rb

Instance Method Summary collapse

Instance Method Details

#cpk_and_predicate(predicates) ⇒ Object 



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# File 'lib/composite_primary_keys/composite_predicates.rb', line 7

def cpk_and_predicate(predicates)
  if predicates.length == 1
    predicates.first
  else
    Arel::Nodes::And.new(predicates)
  end
end

#cpk_id_predicate(table, keys, values) ⇒ Object 



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# File 'lib/composite_primary_keys/composite_predicates.rb', line 34

def cpk_id_predicate(table, keys, values)
  # We zip on values then keys in case values are not provided for each key field
  eq_predicates = values.zip(keys).map do |value, key|
    table[key].eq(value)
  end
  cpk_and_predicate(eq_predicates)
end

#cpk_in_predicate(table, primary_keys, ids) ⇒ Object 



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# File 'lib/composite_primary_keys/composite_predicates.rb', line 53

def cpk_in_predicate(table, primary_keys, ids)
  if primary_keys.length == 2
    cpk_in_predicate_with_grouped_keys(table, primary_keys, ids)
  else
    cpk_in_predicate_with_non_grouped_keys(table, primary_keys, ids)
  end
end

#cpk_in_predicate_with_grouped_keys(table, primary_keys, ids) ⇒ Object 



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# File 'lib/composite_primary_keys/composite_predicates.rb', line 69

def cpk_in_predicate_with_grouped_keys(table, primary_keys, ids)
  keys_by_first_column_name = Hash.new { |hash, key| hash[key] = [] }
  keys_by_second_column_name = Hash.new { |hash, key| hash[key] = [] }

  ids.map.each do |first_key_part, second_key_part|
    keys_by_first_column_name[first_key_part] << second_key_part
    keys_by_second_column_name[second_key_part] << first_key_part
  end

  low_cardinality_column_name, high_cardinality_column_name, groups = \
    if keys_by_first_column_name.size <= keys_by_second_column_name.size
      [primary_keys.first, primary_keys.second, keys_by_first_column_name]
    else
      [primary_keys.second, primary_keys.first, keys_by_second_column_name]
    end

  and_predicates = groups.map do |low_cardinality_value, high_cardinality_values|
    non_nil_high_cardinality_values = high_cardinality_values.compact
    in_clause = table[high_cardinality_column_name].in(non_nil_high_cardinality_values)
    inclusion_clauses = if non_nil_high_cardinality_values.size != high_cardinality_values.size
                          Arel::Nodes::Grouping.new(
                            Arel::Nodes::Or.new(
                              in_clause,
                              table[high_cardinality_column_name].eq(nil)
                            )
                          )
                        else
                          in_clause
                        end

    Arel::Nodes::And.new(
      [
        table[low_cardinality_column_name].eq(low_cardinality_value),
        inclusion_clauses
      ]
    )
  end

  cpk_or_predicate(and_predicates)
end

#cpk_in_predicate_with_non_grouped_keys(table, primary_keys, ids) ⇒ Object 



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# File 'lib/composite_primary_keys/composite_predicates.rb', line 61

def cpk_in_predicate_with_non_grouped_keys(table, primary_keys, ids)
  and_predicates = ids.map do |id|
    cpk_id_predicate(table, primary_keys, id)
  end

  cpk_or_predicate(and_predicates)
end

#cpk_join_predicate(table1, key1, table2, key2) ⇒ Object 



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# File 'lib/composite_primary_keys/composite_predicates.rb', line 42

def cpk_join_predicate(table1, key1, table2, key2)
  key1_fields = Array(key1).map {|key| table1[key]}
  key2_fields = Array(key2).map {|key| table2[key]}

  eq_predicates = key1_fields.zip(key2_fields).map do |key_field1, key_field2|
    key_field2 = Arel::Nodes::Quoted.new(key_field2) unless Arel::Attributes::Attribute === key_field2
    key_field1.eq(key_field2)
  end
  cpk_and_predicate(eq_predicates)
end

#cpk_or_predicate(predicates, group = true) ⇒ Object 



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# File 'lib/composite_primary_keys/composite_predicates.rb', line 15

def cpk_or_predicate(predicates, group = true)
  if predicates.length <= 1
    predicates.first
  else
    split_point = predicates.length / 2
    predicates_first_half = predicates[0...split_point]
    predicates_second_half = predicates[split_point..-1]

    or_predicate = ::Arel::Nodes::Or.new(cpk_or_predicate(predicates_first_half, false),
                                         cpk_or_predicate(predicates_second_half, false))

    if group
      ::Arel::Nodes::Grouping.new(or_predicate)
    else
      or_predicate
    end
  end
end