Postgresql 中文操作指南

46.5. Trigger Functions #

当函数用作触发器时,字典 TD 包含与触发器相关的值:

When a function is used as a trigger, the dictionary TD contains trigger-related values:

  • TD["event"]

    • contains the event as a string: INSERT, UPDATE, DELETE, or TRUNCATE.

  • TD["when"]

    • contains one of BEFORE, AFTER, or INSTEAD OF.

  • TD["level"]

    • contains ROW or STATEMENT.

  • TD["new"]__TD["old"]

    • For a row-level trigger, one or both of these fields contain the respective trigger rows, depending on the trigger event.

  • TD["name"]

    • contains the trigger name.

  • TD["table_name"]

    • contains the name of the table on which the trigger occurred.

  • TD["table_schema"]

    • contains the schema of the table on which the trigger occurred.

  • TD["relid"]

    • contains the OID of the table on which the trigger occurred.

  • TD["args"]

    • If the CREATE TRIGGER command included arguments, they are available in TD["args"][0] to TD["args"][_n-1]_.

如果 TD["when"]BEFOREINSTEAD OF,并且 TD["level"]ROW,则您可以从 Python 函数返回 None"OK" 以指示该行未修改,"SKIP" 以中止事件,或者如果 TD["event"]INSERTUPDATE,则可以返回 "MODIFY" 以表明您已修改新行。否则,将忽略返回值。

If TD["when"] is BEFORE or INSTEAD OF and TD["level"] is ROW, you can return None or "OK" from the Python function to indicate the row is unmodified, "SKIP" to abort the event, or if TD["event"] is INSERT or UPDATE you can return "MODIFY" to indicate you’ve modified the new row. Otherwise the return value is ignored.