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* Performance on writable views
@ 2007-08-08 12:40 Enrico Weigelt <weigelt@metux.de>
2007-08-11 07:42 ` Re: Performance on writable views Heikki Linnakangas <heikki@enterprisedb.com>
0 siblings, 1 reply; 4+ messages in thread
From: Enrico Weigelt @ 2007-08-08 12:40 UTC (permalink / raw)
To: pgsql-sql; postgresql performance list <pgsql-performance@postgresql.org>
Hi folks,
I'm often using writable views as interfaces to clients, so
they only see "virtual" objects and never have to cope with
the actual storage, ie. to give some client an totally
denormalized view of certain things, containing only those
information required for certain kind of operations.
This method is nice for creating easy and robust client
interfaces - internal schema changes are not visible to
the client. In situations when many, many clients - often
coded/maintained by different people - have to access an
database which is still under development (typical for
many inhouse applications), it helps to circument interface
instabilities.
Now I've got the strange feeling that this makes updates
slow, since it always has to run the whole view query to
fetch an record to be updated (ie. to get OLD.*).
Could anyone with some deep insight please give me some
details about that issue ?
cu
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^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Performance on writable views
2007-08-08 12:40 Performance on writable views Enrico Weigelt <weigelt@metux.de>
@ 2007-08-11 07:42 ` Heikki Linnakangas <heikki@enterprisedb.com>
2007-08-11 13:58 ` Re: Performance on writable views Joshua D. Drake <jd@commandprompt.com>
0 siblings, 1 reply; 4+ messages in thread
From: Heikki Linnakangas @ 2007-08-11 07:42 UTC (permalink / raw)
To: pgsql-sql; postgresql performance list <pgsql-performance@postgresql.org>
Enrico Weigelt wrote:
> I'm often using writable views as interfaces to clients, so
> they only see "virtual" objects and never have to cope with
> the actual storage, ie. to give some client an totally
> denormalized view of certain things, containing only those
> information required for certain kind of operations.
>
> This method is nice for creating easy and robust client
> interfaces - internal schema changes are not visible to
> the client. In situations when many, many clients - often
> coded/maintained by different people - have to access an
> database which is still under development (typical for
> many inhouse applications), it helps to circument interface
> instabilities.
>
> Now I've got the strange feeling that this makes updates
> slow, since it always has to run the whole view query to
> fetch an record to be updated (ie. to get OLD.*).
There is some overhead in rewriting the query, but it shouldn't be
significantly slower than issuing the statements behind the view
directly. I wouldn't worry about it, unless you have concrete evidence
that it's causing problems.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Performance on writable views
2007-08-08 12:40 Performance on writable views Enrico Weigelt <weigelt@metux.de>
2007-08-11 07:42 ` Re: Performance on writable views Heikki Linnakangas <heikki@enterprisedb.com>
@ 2007-08-11 13:58 ` Joshua D. Drake <jd@commandprompt.com>
2007-08-13 22:17 ` Re: Performance on writable views Jim Nasby <decibel@decibel.org>
0 siblings, 1 reply; 4+ messages in thread
From: Joshua D. Drake @ 2007-08-11 13:58 UTC (permalink / raw)
To: Heikki Linnakangas <heikki@enterprisedb.com>; +Cc: pgsql-sql; postgresql performance list <pgsql-performance@postgresql.org>
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Heikki Linnakangas wrote:
> Enrico Weigelt wrote:
>> I'm often using writable views as interfaces to clients, so
>> they only see "virtual" objects and never have to cope with
>> the actual storage, ie. to give some client an totally
>> denormalized view of certain things, containing only those
>> information required for certain kind of operations.
>> Now I've got the strange feeling that this makes updates
>> slow, since it always has to run the whole view query to
>> fetch an record to be updated (ie. to get OLD.*).
>
> There is some overhead in rewriting the query, but it shouldn't be
> significantly slower than issuing the statements behind the view
> directly. I wouldn't worry about it, unless you have concrete evidence
> that it's causing problems.
I don't know about that, at least when using rules for partitioning the
impact can be significant in comparison to triggers.
It may make sense for him to push this stuff to stored procs instead.
Joshua D. Drake
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^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Performance on writable views
2007-08-08 12:40 Performance on writable views Enrico Weigelt <weigelt@metux.de>
2007-08-11 07:42 ` Re: Performance on writable views Heikki Linnakangas <heikki@enterprisedb.com>
2007-08-11 13:58 ` Re: Performance on writable views Joshua D. Drake <jd@commandprompt.com>
@ 2007-08-13 22:17 ` Jim Nasby <decibel@decibel.org>
0 siblings, 0 replies; 4+ messages in thread
From: Jim Nasby @ 2007-08-13 22:17 UTC (permalink / raw)
To: Joshua D. Drake <jd@commandprompt.com>; +Cc: Heikki Linnakangas <heikki@enterprisedb.com>; pgsql-sql; postgresql performance list <pgsql-performance@postgresql.org>
On Aug 11, 2007, at 8:58 AM, Joshua D. Drake wrote:
> Heikki Linnakangas wrote:
>> Enrico Weigelt wrote:
>>> I'm often using writable views as interfaces to clients, so
>>> they only see "virtual" objects and never have to cope with
>>> the actual storage, ie. to give some client an totally
>>> denormalized view of certain things, containing only those
>>> information required for certain kind of operations.
>
>>> Now I've got the strange feeling that this makes updates
>>> slow, since it always has to run the whole view query to
>>> fetch an record to be updated (ie. to get OLD.*).
>>
>> There is some overhead in rewriting the query, but it shouldn't be
>> significantly slower than issuing the statements behind the view
>> directly. I wouldn't worry about it, unless you have concrete
>> evidence
>> that it's causing problems.
>
> I don't know about that, at least when using rules for partitioning
> the
> impact can be significant in comparison to triggers.
That's because you have to re-evaluate the input query for each rule
that's defined, so even if you only have rules for 2 partitions in a
table (which is really about the minimum you can have, at least for
some period of overlap surrounding the time when you switch to a new
partition), you're looking at evaluating every input query twice.
In this case, the rules presumably are just simply re-directing DML,
so there'd only be one rule in play at a time. That means the only
real overhead is in the rewrite engine.
--
Decibel!, aka Jim Nasby decibel@decibel.org
EnterpriseDB http://enterprisedb.com 512.569.9461 (cell)
^ permalink raw reply [nested|flat] 4+ messages in thread
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-- links below jump to the message on this page --
2007-08-08 12:40 Performance on writable views Enrico Weigelt <weigelt@metux.de>
2007-08-11 07:42 ` Heikki Linnakangas <heikki@enterprisedb.com>
2007-08-11 13:58 ` Joshua D. Drake <jd@commandprompt.com>
2007-08-13 22:17 ` Jim Nasby <decibel@decibel.org>
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