[Pgpool-hackers] First try at rephrasing the documentation

[Marc Cousin]

The Monday 20 December 2010 10:13:01, Tatsuo Ishii wrote :
> > I will try to answer your TODO items one by one following emals...
Ok. Here is a patch with corrections corresponding to your answers, to be 
applied to the file provided in the previous email.

> 
> TODO : what does this refer to, there is no 3 in the array ?
> A: It referes to "row mode".
Ok, added.

> 
> TODO : is that true ? It seems to me the JDBC driver starts a
> transaction only on first DDL query (in read committed mode at least).
> 
> A: Really? I do not observe what you said with
> postgresql-8.4-701.jdbc4.jar.
I've just checked, and I was mistaken :)

> 
> TODO: Are DDL queries accounted for in the load balancing algorithm ?
> A: Yes.
Corrected
> 
> TODO: can a table be non-distributed and non-replicated, and still be
> used in parallel mode ?
> A: Not sure. will check.
Ok
> 
> TODO: should we define 'pool' in this context ? I find it a bit confusing
> A: The reason why we use 'pool' is just for a historical reason...
Ok, so I've put a definition, tell me if I'm wrong

> 
> TODO: Should be explained in more detail. I guess it's only for the
> 'rsync' method, not PITR…
> A: You are correct.
Modified
> 
> TODO: What is the point of 'flushing the sequences' ? Don't we trust
> WAL recovery ?
> A: PostgreSQL does not log sequence value whenever it counts
> up. Instead it logs 'discretely'. So just redoing from WAL, it's
> possible that slave loses upto 32 sequences. See
> src/backend/commands/sequence.c.
I still don't get it. The purpose of this is just to avoid having a hole of 32 
values in the sequence ? Or is it useful in replication mode and not in 
master-slave? Because having a hole in a sequence is something that happens 
all the time.

> 
> TODO: contradiction in the previous sentence md5 is supported by using
> "pool_passwd".
> A: You are correct.
Yes, but is clear text password supported or not ? :)

> 
> TODO: what happens then ? Is it rejected ?
> A: No. Inconsistent values will be inserted.
Ok, corrected

> 
> TODO: I don't really get this one. Can somebody explain ?
> A: Me neither:-) Let me check...
> 
> <p>The USING CLAUSE is converted to an ON CLAUSE by the query rewrite
> process. Therefore, when "*" is used at target list, the row of the same
> column name appears.</p> TODO: What does it mean ?
> A: I don't know neither:-) Let me check...
> 
> TODO: This following section may be completely false. I tried to
> understand the general meaning of the original text, and look into
> pgpool's code to understand.
> A: Let me check...
Ok, I'll wait on these 3 ones too.

Marc Cousin
Dalibo
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