From 010a4a6e5f8bf79fe549c3227e9e3e9e567eff1a Mon Sep 17 00:00:00 2001
From: Daniel Alfaro <daniel@software.com>
Date: Mon, 29 Mar 2021 10:43:53 -0700
Subject: [PATCH] Add support for check_constraints with the same name on
 different tables

- MariaDB allows the use of the same check_constraint name as long as it
 is on a different table. This is done by adding a new column to the
 information_schema.check_constraints table with name table_name.
---
 .../abstract_mysql_adapter.rb                 |  5 +++-
 activerecord/test/cases/helper.rb             |  9 +++++++
 .../cases/migration/check_constraint_test.rb  | 25 +++++++++++++++++++
 3 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
index 0a53b298fd..637358807c 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -427,7 +427,7 @@ module ActiveRecord
         if supports_check_constraints?
           scope = quoted_scope(table_name)
 
-          chk_info = exec_query(<<~SQL, "SCHEMA")
+          sql = <<~SQL
             SELECT cc.constraint_name AS 'name',
                   cc.check_clause AS 'expression'
             FROM information_schema.check_constraints cc
@@ -437,6 +437,9 @@ module ActiveRecord
               AND tc.table_name = #{scope[:name]}
               AND cc.constraint_schema = #{scope[:schema]}
           SQL
+          sql += " AND cc.table_name = #{scope[:name]}" if mariadb?
+
+          chk_info = exec_query(sql, "SCHEMA")
 
           chk_info.map do |row|
             options = {
diff --git a/activerecord/test/cases/helper.rb b/activerecord/test/cases/helper.rb
index 48c7409bcc..31e3bfc07a 100644
--- a/activerecord/test/cases/helper.rb
+++ b/activerecord/test/cases/helper.rb
@@ -54,6 +54,15 @@ def supports_default_expression?
   end
 end
 
+def supports_non_unique_constraint_name?
+  if current_adapter?(:Mysql2Adapter)
+    conn = ActiveRecord::Base.connection
+    conn.mariadb?
+  else
+    false
+  end
+end
+
 %w[
   supports_savepoints?
   supports_partial_index?
diff --git a/activerecord/test/cases/migration/check_constraint_test.rb b/activerecord/test/cases/migration/check_constraint_test.rb
index 7ce8c7f781..153c994a8f 100644
--- a/activerecord/test/cases/migration/check_constraint_test.rb
+++ b/activerecord/test/cases/migration/check_constraint_test.rb
@@ -18,10 +18,16 @@ if ActiveRecord::Base.connection.supports_check_constraints?
             t.integer :price
             t.integer :quantity
           end
+
+          @connection.create_table "purchases", force: true do |t|
+            t.integer :price
+            t.integer :quantity
+          end
         end
 
         teardown do
           @connection.drop_table "trades", if_exists: true rescue nil
+          @connection.drop_table "purchases", if_exists: true rescue nil
         end
 
         def test_check_constraints
@@ -56,6 +62,25 @@ if ActiveRecord::Base.connection.supports_check_constraints?
           end
         end
 
+        if supports_non_unique_constraint_name?
+          def test_add_constraint_with_same_name_to_different_table
+            @connection.add_check_constraint :trades, "quantity > 0", name: "greater_than_zero"
+            @connection.add_check_constraint :purchases, "quantity > 0", name: "greater_than_zero"
+
+            trades_check_constraints = @connection.check_constraints("trades")
+            assert_equal 1, trades_check_constraints.size
+            trade_constraint = trades_check_constraints.first
+            assert_equal "trades", trade_constraint.table_name
+            assert_equal "greater_than_zero", trade_constraint.name
+
+            purchases_check_constraints = @connection.check_constraints("purchases")
+            assert_equal 1, purchases_check_constraints.size
+            purchase_constraint = purchases_check_constraints.first
+            assert_equal "purchases", purchase_constraint.table_name
+            assert_equal "greater_than_zero", purchase_constraint.name
+          end
+        end
+
         def test_add_check_constraint_with_non_existent_table_raises
           e = assert_raises(ActiveRecord::StatementInvalid) do
             @connection.add_check_constraint :refunds, "quantity > 0", name: "quantity_check"