From: | Julien Rouhaud <rjuju123(at)gmail(dot)com> |
---|---|
To: | Jim Finnerty <jfinnert(at)amazon(dot)com> |
Cc: | pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: [survey] New "Stable" QueryId based on normalized query text |
Date: | 2019-08-10 08:00:25 |
Message-ID: | CAOBaU_YPkz_PBJFb6nLHZv2NcPzFeDHAwPPiF0bca+Jn_Q3Kkg@mail.gmail.com |
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Lists: | pgsql-hackers |
On Sat, Aug 10, 2019 at 3:27 AM Jim Finnerty <jfinnert(at)amazon(dot)com> wrote:
>
> I missed this thread. I'd be happy to post the code for what we use as the
> stable query identifier, but we could definitely come up with a more
> efficient algorithm if we're willing to assume that the sql statements are
> the same if and only if the parse tree structure is the same.
>
> Currently what we do for the sql hash is to simply replace all the literals
> and then hash the resulting SQL string
Isn't that what pg_store_plan is already doing? Except that it
removes extraneous whitespaces and put identifiers in uppercase so
that you get a reasonable query identifier.
> you could define a stable identifier for each node type, ignore literal
> constants, and hash fully-qualified object names instead of OIDs. That
> should be pretty fast.
This has been discussed already, and resolving all object names and
qualifier names will add a dramatic overhead for many workloads.
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