Rails 6.1: Add support for if_exists on remove_column (rails-sqlserver#892)

* Add support for "if_exists" on "remove_column"

See
rails/rails@95ed7e7

* add changelog item

Author: mgrunberg

CHANGELOG.md

@@ -16,6 +16,7 @@
 - [#861](https://github.com/rails-sqlserver/activerecord-sqlserver-adapter/pull/861) Fix Rails 6.1 database config
 - [#890](https://github.com/rails-sqlserver/activerecord-sqlserver-adapter/pull/890) Fix removal of invalid ordering from select statements
 - [#881](https://github.com/rails-sqlserver/activerecord-sqlserver-adapter/pull/881) Dump column collation to schema.rb and allow collation changes using column_change
+- [#892](https://github.com/rails-sqlserver/activerecord-sqlserver-adapter/pull/892) Add support for if_exists on remove_column
 
 #### Changed
 

lib/active_record/connection_adapters/sqlserver/schema_statements.rb

@@ -130,8 +130,9 @@ def rename_table(table_name, new_name)
           rename_table_indexes(table_name, new_name)
         end
 
-        def remove_column(table_name, column_name, type = nil, options = {})
+        def remove_column(table_name, column_name, type = nil, **options)
           raise ArgumentError.new("You must specify at least one column name.  Example: remove_column(:people, :first_name)") if column_name.is_a? Array
+          return if options[:if_exists] == true && !column_exists?(table_name, column_name)
 
           remove_check_constraints(table_name, column_name)
           remove_default_constraint(table_name, column_name)