错误：无法识别 json 类型的相等运算符

问：

我收到错误ERROR: could not identify an equality operator for type json

启动 SQL 查询时

update pdfs
set forced_payload = datatable.forced_payload,
    s3_original_path = datatable.s3_original_path,
    s3_image_path = datatable.s3_image_path,
    s3_preview_path = datatable.s3_preview_path,
    s3_original_inbox_path = datatable.s3_original_inbox_path,
    s3_preview_inbox_path = datatable.s3_preview_inbox_path
from (select 43238::integer as id,
             NULL::json as forced_payload,
             NULL::character varying(255) as s3_original_path,
             NULL::character varying(255) as s3_image_path,
             NULL::character varying(255) as s3_preview_path,
             NULL::character varying(255) as s3_original_inbox_path,
             NULL::character varying(255) as s3_preview_inbox_path
      union
      select 43239,
             NULL,
             NULL,
             NULL,
             NULL,
             NULL,
             NULL
     ) as datatable
where pdfs.id = datatable.id;

针对 postregSQL 数据库

我不知道为什么会出现此错误。 我看过其他有此错误的帖子，但它们与此处的使用有关，或者此处并非如此。DISTINCTGROUP_BY

更多背景信息：

我有一个带有 gem bulk_data_methods的 rails 项目，以便仅使用一个 DB 查询更新 DB 中的多条记录。

这是创建上述数据库查询的 Gem。

（Rails 中的完整错误是：ActiveRecord::StatementInvalid: PG::UndefinedFunction: ERROR: could not identify an equality operator for type json)