postgres trigger creation

How do I only create a trigger if it does not exist?

When I do create or r开发者_运维技巧eplace, I get a syntax error so I am looking for a way to test for the existence of a trigger.

I can always select * from pg_trigger, but I am sure there is a more suitable way.

Thanks

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Postgres can conditionally drop a trigger - see the docs. Do this before creating the trigger, then it will always work.

DROP TRIGGER IF EXISTS mytrigger ON mytable;

As Jack points out in the comments, this feature has only been available since 8.2; this has been out for more than four years though, so it should be available in your version.

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CREATE TRIGGER (NameOfTrigger) AFTER INSERT OR UPDATE ON (NameOfTable)   

DROP TRIGGER IF EXISTS (NameOfTrigger) ON (NameOfTable);