Merge pull request rails#43963 from fatkodima/fix-postgres-check-cons…

…traint-expression

Correctly parse complex check constraint expressions for PostgreSQL

activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb

@@ -523,7 +523,7 @@ def check_constraints(table_name) # :nodoc:
           scope = quoted_scope(table_name)
 
           check_info = exec_query(<<-SQL, "SCHEMA")
-            SELECT conname, pg_get_constraintdef(c.oid) AS constraintdef, c.convalidated AS valid
+            SELECT conname, pg_get_constraintdef(c.oid, true) AS constraintdef, c.convalidated AS valid
             FROM pg_constraint c
             JOIN pg_class t ON c.conrelid = t.oid
             WHERE c.contype = 'c'
@@ -535,7 +535,7 @@ def check_constraints(table_name) # :nodoc:
               name: row["conname"],
               validate: row["valid"]
             }
-            expression = row["constraintdef"][/CHECK \({2}(.+)\){2}/, 1]
+            expression = row["constraintdef"][/CHECK \((.+)\)/m, 1]
 
             CheckConstraintDefinition.new(table_name, expression, options)
           end

activerecord/test/cases/migration/check_constraint_test.rb

@@ -37,6 +37,19 @@ def test_check_constraints
           else
             assert_equal "price > discounted_price", constraint.expression
           end
+
+          if current_adapter?(:PostgreSQLAdapter)
+            begin
+              # Test that complex expression is correctly parsed from the database
+              @connection.add_check_constraint(:trades,
+                "CASE WHEN price IS NOT NULL THEN true ELSE false END", name: "price_is_required")
+
+              constraint = @connection.check_constraints("trades").find { |c| c.name == "price_is_required" }
+              assert_includes constraint.expression, "WHEN price IS NOT NULL"
+            ensure
+              @connection.remove_check_constraint(:trades, name: "price_is_required")
+            end
+          end
         end
 
         def test_add_check_constraint