Revert "Allow `:precision` option for time type columns"

This reverts commit 1502caefd30b137fd1a0865be34c5bbf85ba64c1.

The test suite for the mysql adapter broke when this commit was used
with MySQL 5.6.

Conflicts:
	activerecord/CHANGELOG.md

5 files changed, 19 insertions, 21 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
index 0438c95bd7..503b09d1fc 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
@@ -851,12 +851,6 @@ module ActiveRecord
               raise ArgumentError, "Error adding decimal column: precision cannot be empty if scale is specified"
             end
 
-          elsif [:datetime, :time].include?(type) && precision ||= native[:precision]
-            if (0..6) === precision
-              column_type_sql << "(#{precision})"
-            else
-              raise(ActiveRecordError, "No #{native[:name]} type has precision of #{precision}. The allowed range of precision is from 0 to 6")
-            end
           elsif (type != :primary_key) && (limit ||= native.is_a?(Hash) && native[:limit])
             column_type_sql << "(#{limit})"
           end
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index c307189980..ee11c0efa4 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -245,11 +245,6 @@ module ActiveRecord
         false
       end
 
-      # Does this adapter support datetime with precision?
-      def supports_datetime_with_precision?
-        false
-      end
-
       # This is meant to be implemented by the adapters that support extensions
       def disable_extension(name)
       end
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 84bfab43bb..c6cc98d002 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -251,10 +251,6 @@ module ActiveRecord
         version[0] >= 5
       end
 
-      def supports_datetime_with_precision?
-        (version[0] == 5 && version[1] >= 6) || version[0] >= 6
-      end
-
       def native_database_types
         NATIVE_DATABASE_TYPES
       end
@@ -627,6 +623,13 @@ module ActiveRecord
           when 0x1000000..0xffffffff; 'longtext'
           else raise(ActiveRecordError, "No text type has character length #{limit}")
           end
+        when 'datetime'
+          return super unless precision
+
+          case precision
+            when 0..6; "datetime(#{precision})"
+            else raise(ActiveRecordError, "No datetime type has precision of #{precision}. The allowed range of precision is from 0 to 6.")
+          end
         else
           super
         end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
index 503dda60f4..81fde18f64 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
@@ -534,6 +534,13 @@ module ActiveRecord
               when 5..8; 'bigint'
               else raise(ActiveRecordError, "No integer type has byte size #{limit}. Use a numeric with precision 0 instead.")
             end
+          when 'datetime'
+            return super unless precision
+
+            case precision
+              when 0..6; "timestamp(#{precision})"
+              else raise(ActiveRecordError, "No timestamp type has precision of #{precision}. The allowed range of precision is from 0 to 6")
+            end
           else
             super
           end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 6d25b53b21..5a887ea529 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -180,10 +180,6 @@ module ActiveRecord
         true
       end
 
-      def supports_datetime_with_precision?
-        true
-      end
-
       def index_algorithms
         { concurrently: 'CONCURRENTLY' }
       end
@@ -481,6 +477,7 @@ module ActiveRecord
           register_class_with_limit m, 'varbit', OID::BitVarying
           m.alias_type 'timestamptz', 'timestamp'
           m.register_type 'date', Type::Date.new
+          m.register_type 'time', Type::Time.new
 
           m.register_type 'money', OID::Money.new
           m.register_type 'bytea', OID::Bytea.new
@@ -506,8 +503,10 @@ module ActiveRecord
           m.alias_type 'lseg', 'varchar'
           m.alias_type 'box', 'varchar'
 
-          register_class_with_precision m, 'time', Type::Time
-          register_class_with_precision m, 'timestamp', OID::DateTime
+          m.register_type 'timestamp' do |_, _, sql_type|
+            precision = extract_precision(sql_type)
+            OID::DateTime.new(precision: precision)
+          end
 
           m.register_type 'numeric' do |_, fmod, sql_type|
             precision = extract_precision(sql_type)