Обсуждение: Can you please suggest me some links where I can learn:

Can you please suggest me some links where I can learn:

1.       Transaction Isolation in Database

2.       Query procession and possible optimizations.

3.       How to improve query and its performance.

4.       MVCC in detail.

-- 
john r pierce                                      37N 122W
somewhere on the middle of the left coast

M Tarkeshwar Rao <m.tarkeshwar.rao@ericsson.com> wrote:

> I want start contributing in Postgres in code level.

Welcome!  You should probably start with this page and its links:

http://wiki.postgresql.org/wiki/Developer_FAQ

> Can you please suggest me some links where I can learn:
> 1.       Transaction Isolation in Database

http://www.postgresql.org/docs/current/interactive/transaction-iso.html

> 2.       Query procession and possible optimizations.

http://www.postgresql.org/docs/current/interactive/overview.html

http://www.pgcon.org/2011/schedule/attachments/188_Planner%20talk.pdf

http://www.justin.tv/sfpug/b/419326732

> 3.       How to improve query and its performance.

http://wiki.postgresql.org/wiki/Performance_Optimization

> 4.       MVCC in detail.

http://www.slideshare.net/profyclub_ru/mvcc-unmaskedbruce-momjian

--
Kevin Grittner
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

On Thu, Sep 5, 2013 at 10:39 AM, Kevin Grittner <kgrittn@ymail.com> wrote:
> M Tarkeshwar Rao <m.tarkeshwar.rao@ericsson.com> wrote:
>
>> I want start contributing in Postgres in code level.
>
> Welcome!  You should probably start with this page and its links:
>
> http://wiki.postgresql.org/wiki/Developer_FAQ
>
>> Can you please suggest me some links where I can learn:
>> 1.       Transaction Isolation in Database
>
> http://www.postgresql.org/docs/current/interactive/transaction-iso.html
>
>> 2.       Query procession and possible optimizations.
>
> http://www.postgresql.org/docs/current/interactive/overview.html
>
> http://www.pgcon.org/2011/schedule/attachments/188_Planner%20talk.pdf
>
> http://www.justin.tv/sfpug/b/419326732
>
>> 3.       How to improve query and its performance.
>
> http://wiki.postgresql.org/wiki/Performance_Optimization
>
>> 4.       MVCC in detail.
>
> http://www.slideshare.net/profyclub_ru/mvcc-unmaskedbruce-momjian

Another high priority thing to check out is the README files in the
code (this is mentioned tangentially in the developer FAQ).
Personally  (and I'm no expert) I find some parts of the code much
easier to dive into without a lot of surrounding context than others
-- it could take a lifetime to learn it all.  My advise is to start
small and pick a very specific topic and focus on that.

merlin

On 9/5/2013 3:42 PM, Merlin Moncure wrote:
>   My advise is to start
> small and pick a very specific topic and focus on that.

my advise is to first familiarize yourself with the package from the
user perspective before even thinking of diving in and making any
changes.    I say this, because the OP's questions seemed to suggest
they knew very little about PostgreSQL.



--
john r pierce                                      37N 122W
somewhere on the middle of the left coast

Hi,


(13/09/05 22:19), ascot.moss@gmail.com wrote:
> Hi,
>
>  From the pg_xlog folder, I found some files with interesting time stamps: older file names with newer timestamps,
canyou please advise why? 
>
> Set 1: How come 0000000400000F490000008D is 10 minutes newer than 0000000400000F490000008E?
> -rw------- 1 111 115 16777216 Sep  4 15:28 0000000400000F490000008C
> -rw------- 1 111 115 16777216 Sep  4 15:27 0000000400000F490000008D <===
> -rw------- 1 111 115 16777216 Sep  4 15:17 0000000400000F490000008E <====
> -rw------- 1 111 115 16777216 Sep  4 15:26 0000000400000F490000008F
> -rw------- 1 111 115 16777216 Sep  4 15:27 0000000400000F4900000090

WAL files will be recycled.
For example:

sampledb=# select pg_xlogfile_name(pg_current_xlog_location());
      pg_xlogfile_name
--------------------------
  000000010000000000000004
(1 row)

-rw-------.  1 postgres postgres 16777216 Sep  6 10:55
000000010000000000000001
-rw-------.  1 postgres postgres 16777216 Sep  6 10:56
000000010000000000000002
-rw-------.  1 postgres postgres 16777216 Sep  6 10:57
000000010000000000000003
-rw-------.  1 postgres postgres 16777216 Sep  6 10:58
000000010000000000000004  <--- current WAL

After a few minutes,

sampledb=# select pg_xlogfile_name(pg_current_xlog_location());
      pg_xlogfile_name
--------------------------
  000000010000000000000006
(1 row)

-rw-------.  1 postgres postgres 16777216 Sep  6 11:01
000000010000000000000004 <-- Time of the last write.
-rw-------.  1 postgres postgres 16777216 Sep  6 11:02
000000010000000000000005
-rw-------.  1 postgres postgres 16777216 Sep  6 11:02
000000010000000000000006 <-- current WAL
-rw-------.  1 postgres postgres 16777216 Sep  6 10:55
000000010000000000000007 <-- old name is 000000010000000000000001
-rw-------.  1 postgres postgres 16777216 Sep  6 10:56
000000010000000000000008 <-- old name is 000000010000000000000002
-rw-------.  1 postgres postgres 16777216 Sep  6 10:57
000000010000000000000009 <-- old name is 000000010000000000000003


Timing of recycling depends on the situation. If the time stamp of
current WAL file is the most recent compared with other WAL files, there
is no contradiction.
(I wonder that the time stamp of 0000000400000F490000008C is the most
recent.)



> Set 2: why files,  0000000400000F48000000FD,  0000000400000F48000000FE and 0000000400000F4900000000, are not reused?
> 1) -rw------- 1 postgres postgres 16777216 Sep  4 23:07 0000000400000F48000000FA
> 2) -rw------- 1 postgres postgres 16777216 Sep  4 23:08 0000000400000F48000000FB
> 3) -rw------- 1 postgres postgres 16777216 Sep  4 23:09 0000000400000F48000000FC  <===
> 4) -rw------- 1 postgres postgres 16777216 Sep  4 14:47 0000000400000F48000000FD  <====
> 5) -rw------- 1 postgres postgres 16777216 Sep  4 14:46 0000000400000F48000000FE
> 6) -rw------- 1 postgres postgres 16777216 Sep  4 14:46 0000000400000F4900000000

This is the specification of WAL. This specification changes from 9.3.


regards