Option for ignored columns on update

.ruby-version

@@ -1 +1 @@
-ruby-2.2.4
+ruby-2.4.4

.travis.yml

@@ -1,8 +1,11 @@
 language: ruby
 rvm:
-  - 2.2
-  - 2.3
   - 2.4
   - 2.5
+  - 2.6
+  - 2.7
   - ruby-head
 script: bundle exec rake
+jobs:
+  allow_failures:
+  - rvm: ruby-head

Gemfile.lock

@@ -125,4 +125,4 @@ DEPENDENCIES
   sqlite3
 
 BUNDLED WITH
-   1.14.6
+   2.1.4

README.md

@@ -174,6 +174,28 @@ Book.bulk_insert(*destination_columns, update_duplicates: %w[title]) do |worker|
 end
 ```
 
+### Ignored Columns On Update (MySQL, PostgreSQL)
+
+When there is a conflict in _insert_ and you want to instead update those records you would be using the _update_duplicates_ option. Along with that you can also ignore certain columns which you don't want to be updated. For example you may want to ignore `created_at` field during the update.
+
+```ruby
+destination_columns = [:title, :created_at, :updated_at]
+
+# Ignored columns on update (MySQL)
+Book.bulk_insert(*destination_columns, update_duplicates: true, ignored_columns_on_update: %w(created_at)) do |worker|
+  worker.add(...)
+  # ...
+end
+
+# Ignored columns on update (PostgreSQL)
+Book.bulk_insert(*destination_columns, update_duplicates: %w[title], ignored_columns_on_update: %w(created_at)) do |worker|
+  worker.add(...)
+  # ...
+end
+```
+
+You can pass a single column name, or a list of column names to `ignored_columns_on_update`.
+
 ### Return Primary Keys (PostgreSQL, PostGIS)
 
 If you want the worker to store primary keys of inserted records, then you can

lib/bulk_insert.rb

@@ -4,9 +4,9 @@ module BulkInsert
   extend ActiveSupport::Concern
 
   module ClassMethods
-    def bulk_insert(*columns, values: nil, set_size:500, ignore: false, update_duplicates: false, return_primary_keys: false)
+    def bulk_insert(*columns, values: nil, set_size:500, ignore: false, update_duplicates: false, return_primary_keys: false, ignored_columns_on_update: nil)
       columns = default_bulk_columns if columns.empty?
-      worker = BulkInsert::Worker.new(connection, table_name, primary_key, columns, set_size, ignore, update_duplicates, return_primary_keys)
+      worker = BulkInsert::Worker.new(connection, table_name, primary_key, columns, set_size, ignore, update_duplicates, return_primary_keys, ignored_columns_on_update)
 
       if values.present?
         transaction do

lib/bulk_insert/worker.rb

@@ -7,7 +7,7 @@ class Worker
     attr_accessor :adapter_name
     attr_reader :ignore, :update_duplicates, :result_sets
 
-    def initialize(connection, table_name, primary_key, column_names, set_size=500, ignore=false, update_duplicates=false, return_primary_keys=false)
+    def initialize(connection, table_name, primary_key, column_names, set_size=500, ignore=false, update_duplicates=false, return_primary_keys=false, ignored_columns_on_update=nil)
       @connection = connection
       @set_size = set_size
 
@@ -16,12 +16,14 @@ def initialize(connection, table_name, primary_key, column_names, set_size=500,
       @ignore = ignore
       @update_duplicates = update_duplicates
       @return_primary_keys = return_primary_keys
+      @ignored_columns_on_update = Array(ignored_columns_on_update)
 
       columns = connection.columns(table_name)
       column_map = columns.inject({}) { |h, c| h.update(c.name => c) }
 
       @primary_key = primary_key
       @columns = column_names.map { |name| column_map[name.to_s] }
+      @columns_for_update = @columns.reject { |column| @ignored_columns_on_update.include?(column.name)  }
       @table_name = connection.quote_table_name(table_name)
       @column_names = column_names.map { |name| connection.quote_column_name(name) }.join(",")
 
@@ -154,12 +156,12 @@ def on_conflict_statement
       if is_postgres && ignore
         ' ON CONFLICT DO NOTHING'
       elsif is_postgres && update_duplicates
-        update_values = @columns.map do |column|
+        update_values = @columns_for_update.map do |column|
           "#{column.name}=EXCLUDED.#{column.name}"
         end.join(', ')
         ' ON CONFLICT(' + update_duplicates.join(', ') + ') DO UPDATE SET ' + update_values
       elsif adapter_name =~ /^mysql/i && update_duplicates
-        update_values = @columns.map do |column|
+        update_values = @columns_for_update.map do |column|
           "`#{column.name}`=VALUES(`#{column.name}`)"
         end.join(', ')
         ' ON DUPLICATE KEY UPDATE ' + update_values

test/bulk_insert/worker_test.rb

@@ -418,4 +418,38 @@ class BulkInsertWorkerTest < ActiveSupport::TestCase
 
     assert_equal mysql_worker.compose_insert_query, "INSERT  INTO \"testings\" (\"greeting\",\"age\",\"happy\",\"created_at\",\"updated_at\",\"color\") VALUES ('Yo',15,0,NULL,NULL,'chartreuse') ON DUPLICATE KEY UPDATE `greeting`=VALUES(`greeting`), `age`=VALUES(`age`), `happy`=VALUES(`happy`), `created_at`=VALUES(`created_at`), `updated_at`=VALUES(`updated_at`), `color`=VALUES(`color`)"
   end
+
+  test "mysql adapter can ignore specific columns when updating duplicates" do
+    mysql_worker = BulkInsert::Worker.new(
+      Testing.connection,
+      Testing.table_name,
+      'id',
+      %w(greeting age happy created_at updated_at color),
+      500, # batch size
+      false, # ignore
+      true, # update_duplicates
+      false, # return_primary_keys
+      %w(created_at)) # ignored_columns_on_update
+    mysql_worker.adapter_name = 'MySQL'
+    mysql_worker.add ["Yo", 15, false, nil, nil]
+
+    assert_equal mysql_worker.compose_insert_query, "INSERT  INTO \"testings\" (\"greeting\",\"age\",\"happy\",\"created_at\",\"updated_at\",\"color\") VALUES ('Yo',15,0,NULL,NULL,'chartreuse') ON DUPLICATE KEY UPDATE `greeting`=VALUES(`greeting`), `age`=VALUES(`age`), `happy`=VALUES(`happy`), `updated_at`=VALUES(`updated_at`), `color`=VALUES(`color`)"
+  end
+
+  test "pgsql_worker adapter can ignore specific columns when updating duplicates" do
+    pgsql_worker = BulkInsert::Worker.new(
+      Testing.connection,
+      Testing.table_name,
+      'id',
+      %w(greeting age happy created_at updated_at color),
+      500, # batch size
+      false, # ignore
+      %w(greeting), # update_duplicates
+      false, # return_primary_keys
+      %w(created_at)) # ignored_columns_on_update
+    pgsql_worker.adapter_name = 'PostgreSQL'
+    pgsql_worker.add ["Yo", 15, false, nil, nil]
+
+    assert_equal pgsql_worker.compose_insert_query, "INSERT  INTO \"testings\" (\"greeting\",\"age\",\"happy\",\"created_at\",\"updated_at\",\"color\") VALUES ('Yo',15,0,NULL,NULL,'chartreuse') ON CONFLICT(greeting) DO UPDATE SET greeting=EXCLUDED.greeting, age=EXCLUDED.age, happy=EXCLUDED.happy, updated_at=EXCLUDED.updated_at, color=EXCLUDED.color"
+  end
 end