Re: using worker_spi as pattern
| От | Jeremy Finzel |
|---|---|
| Тема | Re: using worker_spi as pattern |
| Дата | |
| Msg-id | CAMa1XUgePedkwTXWYucd4Tw3LSuWWU0D+cGee9ry00ye_tnL3A@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: using worker_spi as pattern (Michael Paquier <michael@paquier.xyz>) |
| Ответы |
Re: using worker_spi as pattern
|
| Список | pgsql-hackers |
If you look at the code of worker_spi.c closely the answer shows up by
itself:
appendStringInfo(&buf,
"CREATE SCHEMA \"%s\" "
"CREATE TABLE \"%s\" ("
" type text CHECK (type IN ('total', 'delta')), "
" value integer)"
"CREATE UNIQUE INDEX \"%s_unique_total\" ON \"%s\" (type) "
"WHERE type = 'total'",
In this case "total" is not a type, it is one of the authorized value in
the value. So just insert an initial tuple like that:
INSERT INTO schema1.counted VALUES ('total', 1);
And then insert periodically for example the following:
INSERT INTO schema1.counted VALUES ('delta', 3);
And then the background worker will sum up the values inserted in
"delta" tuples to the actual "total".
I could not find the table schema1.counted. What confused me is that I ran SELECT worker_spi_launch(1); but it created the schema in the database postgres instead of the current database I am in! Doesn't that seem a bit counter-intuitive? Anyway, I found it now, so I am good to go! Thank you!
> I am trying to use this extension as a pattern for my own background
> worker, but just trying to understand it.
You are right to do so, this is a good learning step.
--
Michael
Since you mention, can anyone elaborate further on the memory leak danger here?
Line 193 in src/test/modules/worker_spi/worker_spi.c read:
# Note some memory might be leaked here.
Is this any reason not to use this pattern in production?
Thanks,
Jeremy
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