| From: | Mark Kirkwood <markir(at)paradise(dot)net(dot)nz> |
|---|---|
| To: | Mark Kirkwood <markir(at)paradise(dot)net(dot)nz> |
| Cc: | "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com>, pgsql-patches(at)postgresql(dot)org, pgsql-docs(at)postgresql(dot)org |
| Subject: | Re: Summary table trigger example race condition |
| Date: | 2006-01-11 02:18:49 |
| Message-ID: | 43C46B09.8080300@paradise.net.nz |
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| Thread: | |
| Lists: | pgsql-docs pgsql-patches |
Mark Kirkwood wrote:
> Jim C. Nasby wrote:
>
>> On Sun, Jan 08, 2006 at 04:13:01PM +1300, Mark Kirkwood wrote:
>>
>>
>>
>> What happens if someone deletes the row between the failed insert and
>> the second update? :)
>>
>
> In this example the rows in the summary table never get deleted by
> DELETE operations on that main one - the trigger just decrements the
> various amounts - i.e DELETE becomes UPDATE, so no problem there.
>
Sorry Jim, I just realized you probably meant someone directly deleting
rows in the summary table itself. Well yes, that would certainly fox it!
I guess I was implicitly considering a use case where the only direct
DML on the summary table would be some sort of ETL process, which would
probably lock out other changes (and re-create the summary table data
afterwards in all likelihood).
Cheers
Mark
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