Merge pull request #846 from ckhsponge/transaction-update-block

TransactionWrite update_fields() with a block

Author: andrykonchin

README.md

@@ -24,8 +24,8 @@ DynamoDB is not like other document-based databases you might know, and
 is very different indeed from relational databases. It sacrifices
 anything beyond the simplest relational queries and transactional
 support to provide a fast, cost-efficient, and highly durable storage
-solution. If your database requires complicated relational queries and
-transaction support, then this modest Gem cannot provide them for you,
+solution. If your database requires complicated relational queries
+then this modest Gem cannot provide them for you
 and neither can DynamoDB. In those cases you would do better to look
 elsewhere for your database needs.
 
@@ -1187,6 +1187,19 @@ Dynamoid::TransactionWrite.execute do |txn|
   # sets the name and title for a user
   # The user is found by id (that equals 1)
   txn.update_fields(User, '1', name: 'bob', title: 'mister')
+
+  # sets the name, increments a count and deletes a field
+  txn.update_fields(User, 1) do |t|
+    t.set(name: 'bob')
+    t.add(article_count: 1)
+    t.delete(:title)
+  end
+
+  # adds to a set of integers and deletes from a set of strings
+  txn.update_fields(User, 2) do |t|
+    t.add(friend_ids: [1, 2])
+    t.delete(child_names: ['bebe'])
+  end
 end
 ```
 

lib/dynamoid/errors.rb

@@ -86,7 +86,16 @@ class InvalidQuery < Error; end
 
     class UnsupportedKeyType < Error; end
 
-    class UnknownAttribute < Error; end
+    class UnknownAttribute < Error
+      attr_reader :model_class, :attribute_name
+
+      def initialize(model_class, attribute_name)
+        super("Attribute #{attribute_name} does not exist in #{model_class}")
+
+        @model_class = model_class
+        @attribute_name = attribute_name
+      end
+    end
 
     class SubclassNotFound < Error; end
 

lib/dynamoid/fields.rb

@@ -291,7 +291,7 @@ def write_attribute(name, value)
       old_value = read_attribute(name)
 
       unless attribute_is_present_on_model?(name)
-        raise Dynamoid::Errors::UnknownAttribute, "Attribute #{name} is not part of the model"
+        raise Dynamoid::Errors::UnknownAttribute.new(self.class, name)
       end
 
       if association = @associations[name]

lib/dynamoid/persistence.rb

@@ -620,8 +620,7 @@ def update_attribute(attribute, value)
     # attributes. Supports following operations: +add+, +delete+ and +set+.
     #
     # Operation +add+ just adds a value for numeric attributes and join
-    # collections if attribute is a collection (one of +array+, +set+ or
-    # +map+).
+    # collections if attribute is a set.
     #
     #   user.update! do |t|
     #     t.add(age: 1, followers_count: 5)
@@ -646,7 +645,7 @@ def update_attribute(attribute, value)
     # {parameter}[https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/LegacyConditionalParameters.AttributeUpdates.html]
     # of +UpdateItem+ operation.
     #
-    # It's an atomic operation. So adding or deleting elements in a collection
+    # It's atomic operations. So adding or deleting elements in a collection
     # or incrementing or decrementing a numeric field is atomic and does not
     # interfere with other write requests.
     #
@@ -716,8 +715,7 @@ def update!(conditions = {})
     # attributes. Supports following operations: +add+, +delete+ and +set+.
     #
     # Operation +add+ just adds a value for numeric attributes and join
-    # collections if attribute is a collection (one of +array+, +set+ or
-    # +map+).
+    # collections if attribute is a set.
     #
     #   user.update do |t|
     #     t.add(age: 1, followers_count: 5)

lib/dynamoid/persistence/update_validations.rb

@@ -7,9 +7,9 @@ module UpdateValidations
       def self.validate_attributes_exist(model_class, attributes)
         model_attributes = model_class.attributes.keys
 
-        attributes.each_key do |attr_name|
-          unless model_attributes.include?(attr_name)
-            raise Dynamoid::Errors::UnknownAttribute, "Attribute #{attr_name} does not exist in #{model_class}"
+        attributes.each_key do |name|
+          unless model_attributes.include?(name)
+            raise Dynamoid::Errors::UnknownAttribute.new(model_class, name)
           end
         end
       end

lib/dynamoid/transaction_write.rb

@@ -8,6 +8,7 @@
 require 'dynamoid/transaction_write/update_fields'
 require 'dynamoid/transaction_write/update_attributes'
 require 'dynamoid/transaction_write/upsert'
+require 'dynamoid/transaction_write/item_updater'
 
 module Dynamoid
   # The class +TransactionWrite+ provides means to perform multiple modifying
@@ -345,6 +346,52 @@ def upsert(model_class, hash_key, range_key = nil, attributes) # rubocop:disable
     #     t.update_fields(User, '1', 'Tylor', age: 26)
     #   end
     #
+    # Updates can also be performed in a block.
+    #
+    #   Dynamoid::TransactionWrite.execute do |t|
+    #     t.update_fields(User, 1) do |u|
+    #       u.add(article_count: 1)
+    #       u.delete(favorite_colors: 'green')
+    #       u.set(age: 27, last_name: 'Tylor')
+    #     end
+    #   end
+    #
+    # Operation +add+ just adds a value for numeric attributes and join
+    # collections if attribute is a set.
+    #
+    #   t.update_fields(User, 1) do |u|
+    #     u.add(age: 1, followers_count: 5)
+    #     u.add(hobbies: ['skying', 'climbing'])
+    #   end
+    #
+    # Operation +delete+ is applied to collection attribute types and
+    # substructs one collection from another.
+    #
+    #   t.update_fields(User, 1) do |u|
+    #     u.delete(hobbies: ['skying'])
+    #   end
+    #
+    # Operation +set+ just changes an attribute value:
+    #
+    #   t.update_fields(User, 1) do |u|
+    #     u.set(age: 21)
+    #   end
+    #
+    # Operation +remove+ removes one or more attributes from an item.
+    #
+    #   t.update_fields(User, 1) do |u|
+    #     u.remove(:age)
+    #   end
+    #
+    # All the operations work like +ADD+, +DELETE+, +REMOVE+, and +SET+ actions supported
+    # by +UpdateExpression+
+    # {parameter}[https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.UpdateExpressions.html]
+    # of +UpdateItem+ operation.
+    #
+    # It's atomic operations. So adding or deleting elements in a collection
+    # or incrementing or decrementing a numeric field is atomic and does not
+    # interfere with other write requests.
+    #
     # Raises a +Dynamoid::Errors::UnknownAttribute+ exception if any of the
     # attributes is not declared in the model class.
     #
@@ -353,8 +400,14 @@ def upsert(model_class, hash_key, range_key = nil, attributes) # rubocop:disable
     # @param range_key [Scalar value] range key value (optional)
     # @param attributes [Hash]
     # @return [nil]
-    def update_fields(model_class, hash_key, range_key = nil, attributes) # rubocop:disable Style/OptionalArguments
-      action = Dynamoid::TransactionWrite::UpdateFields.new(model_class, hash_key, range_key, attributes)
+    def update_fields(model_class, hash_key, range_key = nil, attributes = nil, &block)
+      # given no attributes, but there may be a block
+      if range_key.is_a?(Hash) && !attributes
+        attributes = range_key
+        range_key = nil
+      end
+
+      action = Dynamoid::TransactionWrite::UpdateFields.new(model_class, hash_key, range_key, attributes, &block)
       register_action action
     end
 

lib/dynamoid/transaction_write/item_updater.rb

@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+module Dynamoid
+  class TransactionWrite
+    class ItemUpdater
+      attr_reader :attributes_to_set, :attributes_to_add, :attributes_to_delete, :attributes_to_remove
+
+      def initialize(model_class)
+        @model_class = model_class
+
+        @attributes_to_set = {}
+        @attributes_to_add = {}
+        @attributes_to_delete = {}
+        @attributes_to_remove = []
+      end
+
+      def empty?
+        [@attributes_to_set, @attributes_to_add, @attributes_to_delete, @attributes_to_remove].all?(&:empty?)
+      end
+
+      def set(attributes)
+        validate_attribute_names!(attributes.keys)
+        @attributes_to_set.merge!(attributes)
+      end
+
+      # adds to array of fields for use in REMOVE update expression
+      def remove(*names)
+        validate_attribute_names!(names)
+        @attributes_to_remove += names
+      end
+
+      # increments a number or adds to a set, starts at 0 or [] if it doesn't yet exist
+      def add(attributes)
+        validate_attribute_names!(attributes.keys)
+        @attributes_to_add.merge!(attributes)
+      end
+
+      # deletes a value or values from a set
+      def delete(attributes)
+        validate_attribute_names!(attributes.keys)
+        @attributes_to_delete.merge!(attributes)
+      end
+
+      private
+
+      def validate_attribute_names!(names)
+        names.each do |name|
+          unless @model_class.attributes[name]
+            raise Dynamoid::Errors::UnknownAttribute.new(@model_class, name)
+          end
+        end
+      end
+    end
+  end
+end