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Re: Cluster feature: Start/stop archiving at runtime

From: Greg Smith <greg(at)2ndquadrant(dot)com>
To: Tatsuo Ishii <ishii(at)sraoss(dot)co(dot)jp>
Cc: pgsql-cluster-hackers(at)postgresql(dot)org
Subject: Re: Cluster feature: Start/stop archiving at runtime
Date: 2010-02-28 06:55:59
Message-ID: 4B8A137F.4030902@2ndquadrant.com (view raw or flat)
Thread:
Lists: pgsql-cluster-hackers
Tatsuo Ishii wrote:
>> Since I didn't hear anything about "API into the Parser / Parser as an 
>> independent module", I just wrote my own summary of what I think the 
>> idea was there is and am moving on.  I'll try to track down more info at 
>> PG East next month when I run into some of the people I think care about 
>> this.
>>     
>
> I have took a look at your description. That is totally different from
> what I thought. Statement replication and/or load balancing middle
> ware need to know SQL statement is SELECT or others. If it is a (read
> only) SELECT, it can be routed to standby node of Streaming
> replication clusters for example. For this purpose, such a middle ware
> ought to be able to parse SQL. If PostgreSQL provide its raw parser as
> a C library, it will be very usefull for such middle ware since they
> do not need to re-implement their own SQL parser (as pgpool-II already
> did).
>
>   

I never claimed I really understand what entry was alluding to and just 
made the first wild guess that came to mind.  I'll be happy to replace 
it with the alternate explanation you suggested for what it was intended 
to address.  The part I still don't see is how these two comments in 
that section fit into what you're describing here:

* statement based replication need to replay certain constructs with 
CONSTANT values you provide
* Figure out which you need to replace... quite difficult

Those are the parts I was basing my guess as to the intended application 
here on.  If this is just intended to improve relaying SELECT statements 
over to another node, why would you need to replace anything with 
constants or other values?

-- 
Greg Smith  2ndQuadrant US  Baltimore, MD
PostgreSQL Training, Services and Support
greg(at)2ndQuadrant(dot)com   www.2ndQuadrant.us


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Subject: Re: Cluster feature: Start/stop archiving at runtime
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