[pgpool-hackers: 170] Re: Improvements

[Alexey Fedonin]

Hello.

Sorry for the delay. I'll correct what you said and I'm going to write a
document with implementation details.
But I need time, maybe a week or two.

Best regards,
Alexey Fedonin.

2013/2/10 Tatsuo Ishii <ishii at postgresql.org>

> On more thing. pcp/md.c and pcp/md5.h is a symlink to upper directory
> and shound not be included in the patch.
> --
> Tatsuo Ishii
> SRA OSS, Inc. Japan
> English: http://www.sraoss.co.jp/index_en.php
> Japanese: http://www.sraoss.co.jp
>
> > Thanks.
> >
> > I have tested a little bit your patches and now I would like to hear
> > more details of implementation because your changes are big and hard
> > to follow implementation details for me(especially
> > pool_process_query.c).
> >
> > Also here are some requests:
> >
> > 1) please include doc changes. (i.e. doc/pgpool-en.html)
> >
> > 2) we do not use C++ style codings (we follow the PostgreSQL coding
> >    style). So please do not use '//' comments. Also please do not
> >    declare variable in the middle of blocks. I mean:
> >
> >    if (a < b)
> >    {
> >               int d;
> >
> >               a = 1;
> >               b = 2;
> >               c = 3;
> >               :
> >               :
> >       }
> >
> >       is ok but this is not ok:
> >
> >    if (a < b)
> >    {
> >               a = 1;
> >               b = 2;
> >               int c  = 3;
> >               :
> >               :
> >       }
> > --
> > Tatsuo Ishii
> > SRA OSS, Inc. Japan
> > English: http://www.sraoss.co.jp/index_en.php
> > Japanese: http://www.sraoss.co.jp
> >
> >> Sure.
> >>
> >> Best regards,
> >> Alexey Fedonin.
> >>
> >> 2013/2/1 Tatsuo Ishii <ishii at postgresql.org>
> >>
> >>> Alexey,
> >>>
> >>> I tried to make a diff between current git repo master and you repo in
> >>> github and found yoursis based on a little bit older version of
> >>> repo. Can you please rebase it? Or even better, could you send diff
> >>> against current git repo master?
> >>> --
> >>> Tatsuo Ishii
> >>> SRA OSS, Inc. Japan
> >>> English: http://www.sraoss.co.jp/index_en.php
> >>> Japanese: http://www.sraoss.co.jp
> >>>
> >>> > Hello, everyone!
> >>> >
> >>> > I've added new features and improvements to pgpool (for parallel
> mode)
> >>> > which I would like to contribute as well as get feedback from the
> >>> community.
> >>> > Features:
> >>> >  - Transaction support added (for SELECT * FROM distributed_table);
> >>> >  - CURSORS support added (for distributed tables);
> >>> >  - Dynamic connections to System DB (optional);
> >>> >  - SELECT rewriting fixes (some improvements and some bugfixes).
> >>> >
> >>> > 1) Transactions.
> >>> > When client sends 'BEGIN' statement, pgpool child connects to another
> >>> child
> >>> > and resend all client statements to it, except for 'SELECT ... FROM
> >>> > distributed_table', which executes in usual way. In this case,
> 'SELECT
> >>> ...
> >>> > FROM distributed_table' executes inside the same transaction block as
> >>> well
> >>> > as other statements.
> >>> > The better way would be to use the same child's connections as it
> uses
> >>> for
> >>> > non-distributed SELECTs, but I haven't found the means of doing it.
> >>> >
> >>> > 2) Cursors.
> >>> > For example, we have two nodes and distributed table:
> >>> >  Node 0             Node 1
> >>> >
> >>> >  value              value
> >>> > -------            -------
> >>> >  4                  3
> >>> >  6                  1
> >>> >  8                  7
> >>> >  2                  9
> >>> >  0                  5
> >>> >
> >>> >  a. BEGIN;
> >>> >  b. DECLARE cursor_name CURSOR FOR SELECT value FROM
> distributed_table
> >>> > ORDER BY value;
> >>> >  c. MOVE FORWARD 2 IN cursor_name;
> >>> >  d. FETCH FORWARD 3 IN cursor_name:
> >>> >
> >>> >  value
> >>> > -------
> >>> >  2
> >>> >  3
> >>> >  4
> >>> >
> >>> >  CURSORS work for FORWARD/BACKWARD ALL/(positive number).
> >>> >  Cursors work for any type of distribution, e.g. round-robin.
> >>> >
> >>> >  3) Dynamic connections (optional).
> >>> >  If number of clients is not usually too high, it is not necessary to
> >>> have
> >>> > connections to System DB for free childs.
> >>> >  New parameter 'system_db_dynamic_connection' added to config.
> >>> >  If value of parameter is 0, child works as usual.
> >>> >  If value > 0, child connects to System DB when client connects.
> Also,
> >>> > child without System DB connections sleeps for
> >>> > 'system_db_dynamic_connection' mcs before accepting new client. So
> new
> >>> > client will be accepted by child, which already has connections to
> System
> >>> > DB.
> >>> >
> >>> >  4) SELECT.
> >>> >  SELECT rewriting logic was changed a little, and now more complex
> >>> queries
> >>> > work correctly, such as:
> >>> >   a. SELECT field_1, (SELECT field_2 FROM replicated_table WHERE
> >>> > field_3=S1.field_3) AS field_2 FROM distributed_table S1;
> >>> >   b. (SELECT field_1, (SELECT field_2 FROM replicated_table_1) AS
> field_2
> >>> > FROM distributed_table_1 S1) UNION ALL (SELECT field_1, (SELECT
> field_3
> >>> > FROM replicated_table_2) AS field_3 FROM distributed_table_2 S2)
> ORDER BY
> >>> > field_1;
> >>> >   c. Also, 'ORDER BY + LIMIT + OFFSET' optimization added:
> >>> > SELECT field FROM distributed_table ORDER BY field LIMIT 10 OFFSET
> 100;
> >>> > rewrites into:
> >>> > SELECT "pool_c$1" AS field FROM dblink('host=localhost.localdomain
> >>> > dbname=dbname port=9999 user=username','SELECT pool_parallel("SELECT
> >>> > distributed_table.time FROM distributed_table ORDER BY field LIMIT
> 10 +
> >>> > 100")',false) AS pool_t$0("pool_c$1" field_type) ORDER BY "pool_c$1"
> >>> OFFSET
> >>> > 100 LIMIT 10;
> >>> >   d. some bugfixes.
> >>> >
> >>> > If you are interested in, I could explain each change in detail.
> >>> >
> >>> > Source code is available at
> https://github.com/afedonin/repo-test.git
> >>> >
> >>> > P.S. All changes was made and tested for parallel_mode.
> >>> > P.P.S. I don't know pgpool as good as you, so I appreciate any
> feedback.
> >>> >
> >>> > Best regards,
> >>> > Alexey Fedonin.
> >>>
> > _______________________________________________
> > pgpool-hackers mailing list
> > pgpool-hackers at pgpool.net
> > http://www.pgpool.net/mailman/listinfo/pgpool-hackers
>
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