Re: function cache effect still happening? - Mailing list pgsql-general
| From | Fernando Moreno |
|---|---|
| Subject | Re: function cache effect still happening? |
| Date | |
| Msg-id | b1c45530805261208y3661fd13j962ebdc34354babd@mail.gmail.com Whole thread Raw |
| In response to | Re: function cache effect still happening? ("Gurjeet Singh" <singh.gurjeet@gmail.com>) |
| Responses |
Re: function cache effect still happening?
(Kevin Neufeld <kneufeld@refractions.net>)
Re: function cache effect still happening? ("Merlin Moncure" <mmoncure@gmail.com>) |
| List | pgsql-general |
2008/5/26 Gurjeet Singh <singh.gurjeet@gmail.com>:
Thanks for your reply. I've been digging the list archive and I think EXECUTE is the best workaround, at least better than restarting the connection, creating the function again or restarting the server (!!). By the way, this flushing-function-cache thing seems to be an almost esoteric topic, because I wasn't able to find anything clear, unless you were talking about it more as a consequence than an action by itself.
On the other hand, perhaps this problem could have been avoided by creating the same function in every schema. That way the function cache and query plans would be harmless. Am I right?
Cheers.
On Mon, May 26, 2008 at 9:49 PM, Fernando Moreno <azazel.7@gmail.com> wrote:--Hi everyone, a few months ago I was still using Postgresql 8.2 and had the problem described here: http://www.postgresql.org/docs/faqs.FAQ.html#item4.19 , that time I solved it using EXECUTE for all sentences accessing temporary tables. Right now I'm using 8.3, the scenario is a little different but the problem is the same. I have many schemas with the same structure (tables, views and one trigger), and two functions in the public schema which insert and delete data from them, the INSERT and DELETE sentences are hard-coded. Every schema represents a store from the same company.
The idea is that just by changing the search_path value to something like "schema1,public", it's possible to execute the functions and to process data for any schema (one at a time). But the problem is here: through the client app, a user invokes one of these functions on a given schema (schema1), then requests a "store change", actually setting the search_path to use another schema (schema2) and again, executes any of the functions that access the schema tables, BUT the function seems to be still linked to the first schema, so new records are added to the wrong schema and delete operations don't find the right record. EXECUTE will save the day again, but I'd like to know if this is considered a known bug even when it was apparently fixed.
I don't think it can be categorized as a bug! This is happening because all the DML queries are prepared upon first execution, and the plan stores the unique identifiers (OIDs) of the objects and not the names of the objects. Upon changing search_path, the function cache is not flushed, and hence the query plans are still operating on the same objects.
I see two possibilities,
i) Flush function cache (only the query plans, if possible) when changing search_path.
ii) Give users the ability to flush the function cache at will.
I don't think (ii) will have much backing, but (i) does make some sense.
Best regards,
gurjeet[.singh]@EnterpriseDB.com
singh.gurjeet@{ gmail | hotmail | indiatimes | yahoo }.com
EnterpriseDB http://www.enterprisedb.com
Mail sent from my BlackLaptop device
Thanks for your reply. I've been digging the list archive and I think EXECUTE is the best workaround, at least better than restarting the connection, creating the function again or restarting the server (!!). By the way, this flushing-function-cache thing seems to be an almost esoteric topic, because I wasn't able to find anything clear, unless you were talking about it more as a consequence than an action by itself.
On the other hand, perhaps this problem could have been avoided by creating the same function in every schema. That way the function cache and query plans would be harmless. Am I right?
Cheers.
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