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:
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TD["event"]
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contains the event as a string: INSERT, UPDATE, DELETE, or TRUNCATE.
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TD["when"]
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contains one of BEFORE, AFTER, or INSTEAD OF.
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TD["level"]
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contains ROW or STATEMENT.
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TD["new"]__TD["old"]
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For a row-level trigger, one or both of these fields contain the respective trigger rows, depending on the trigger event.
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TD["name"]
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contains the trigger name.
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TD["table_name"]
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contains the name of the table on which the trigger occurred.
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TD["table_schema"]
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contains the schema of the table on which the trigger occurred.
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TD["relid"]
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contains the OID of the table on which the trigger occurred.
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TD["args"]
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If the CREATE TRIGGER command included arguments, they are available in TD["args"][0] to TD["args"][_n-1]_.
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如果 TD["when"] 是 BEFORE 或 INSTEAD OF,并且 TD["level"] 是 ROW,则您可以从 Python 函数返回 None 或 "OK" 以指示该行未修改,"SKIP" 以中止事件,或者如果 TD["event"] 是 INSERT 或 UPDATE,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.