PostgreSQL 为什么临时文件这么大，怎么处理

如果有笛卡尔乘积或者大表的排序或者hash表的操作，会使用临时文件来存储中间过程的数据。如果频繁的进行上述操作，临时文件会快速增长。重启PostgreSQL可以解决这个问题。另外建议用户设置temp_file_limit 为磁盘空间的10 %。

temp_file_limit的详细解释如下：
Enter temp_file_limit, a parameter added by Mark Kirkwood to PostgreSQL 9.2. This is a limit on per-session usage of temporary files for sorts, hashes, and similar operations.
If a user goes over the limit, their query gets cancelled and they see an error. This is an excellent way to prevent a single user, or a bad application change, from DOSing your database server. Set it to something high; I'm using 10GB or 20GB, or 10% of available disks space, whichever is less. But even a high limit like that will save you from some unexpected downtime.