Add precision to time, datetime, and timestamp field types

Author: ankane

ext/mysql2/result.c

@@ -287,17 +287,29 @@ static VALUE rb_mysql_result_fetch_field_type(VALUE self, unsigned int idx) {
         rb_field_type = rb_sprintf("double(%ld,%d)", field->length, field->decimals);
         break;
       case MYSQL_TYPE_TIME:         // MYSQL_TIME
-        rb_field_type = rb_str_new_cstr("time");
+        if (field->decimals == 0) {
+          rb_field_type = rb_str_new_cstr("time");
+        } else {
+          rb_field_type = rb_sprintf("time(%d)", field->decimals);
+        }
         break;
       case MYSQL_TYPE_DATE:         // MYSQL_TIME
       case MYSQL_TYPE_NEWDATE:      // MYSQL_TIME
         rb_field_type = rb_str_new_cstr("date");
         break;
       case MYSQL_TYPE_DATETIME:     // MYSQL_TIME
-        rb_field_type = rb_str_new_cstr("datetime");
+        if (field->decimals == 0) {
+          rb_field_type = rb_str_new_cstr("datetime");
+        } else {
+          rb_field_type = rb_sprintf("datetime(%d)", field->decimals);
+        }
         break;
       case MYSQL_TYPE_TIMESTAMP:    // MYSQL_TIME
-        rb_field_type = rb_str_new_cstr("timestamp");
+        if (field->decimals == 0) {
+          rb_field_type = rb_str_new_cstr("timestamp");
+        } else {
+          rb_field_type = rb_sprintf("timestamp(%d)", field->decimals);
+        }
         break;
       case MYSQL_TYPE_DECIMAL:      // char[]
       case MYSQL_TYPE_NEWDECIMAL:   // char[]

spec/mysql2/result_spec.rb

@@ -199,6 +199,22 @@
       expect(result.field_types).to eql(expected_types)
     end
 
+    it "should return precision for timestamps" do
+      result = @client.query(
+        "SELECT now(), " \
+        "cast(now() as datetime(3)), " \
+        "cast(now() as datetime(6))",
+      )
+
+      expected_types = %w[
+        timestamp
+        datetime(3)
+        datetime(6)
+      ]
+
+      expect(result.field_types).to eql(expected_types)
+    end
+
     it "should return json type on mysql 8.0" do
       next unless /8.\d+.\d+/ =~ @client.server_info[:version]