Обсуждение: select regexp_matches('a a a', '([a-z]) a','g');

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Compose a new message instead.

Marc Mamin wrote:

> I have a string that contains a serie of chars, separated by single
> spaces.
>
> e.g 'a b x n r a b c b'
>
> Having such a string, I d'like to get a list of all predecessors of a
> given character.
> In the example, the predecessors of b  are a,a,c.

OK, so wherever `b' occurs, you want the character at index `b -2'.

> select regexp_matches('a a a', '([a-z]) a','g');
> => {"a "} only

The issue is that regular expressions don't like to overlap matches. The
first match consumes _two_ leading `a' characters.

What you need is a zero-width lookahead assertion, available in
Perl-style extended regular expressions.  Handily, recent PostgreSQL
versions support these, so you can write:

test=> select regexp_matches( 'a a a', '([a-z]) (?=a)', 'g');regexp_matches
----------------{a}{a}
(2 rows)

--
Craig Ringer

Hello,

I have two databases db1 and db2 with the same database structure on
different systems with no network connection. In the first system with the
db1 database user updates the master data. At the end of every day, the user
needs to take the backup of updated data of master tables on db1 and update
the data on another system with db2 database.

We can't use WAL as in this as we want to take incremental backup of few
tables only and can't use slony as there is no network connection between
the systems.

Please suggest some solution.

Thanks,
Jyoti 

Wow, I'm impressed. Let me quote part of the message you just replied to
with a TOTALLY UNRELATED NEW THREAD:

"First: Please don't reply to an existing message to create a new
thread. Your mail client copies the replied-to message ID into the
References: header, and well-implemented mail clients will thread your
message under a now-unrelated thread.

Compose a new message instead."

--
Craig Ringer

Craig Ringer wrote:

... something kinda rude, in retrospect. Sorry. Unpleasantness is going
around in my immediate environment, and I'm apparently prickly and grumpy.

--
Craig Ringer

Jyoti Seth wrote:
> Hello,
> 
> I have two databases db1 and db2 with the same database structure on
> different systems with no network connection. In the first system with the
> db1 database user updates the master data. At the end of every day, the user
> needs to take the backup of updated data of master tables on db1 and update
> the data on another system with db2 database.
> 
> We can't use WAL as in this as we want to take incremental backup of few
> tables only and can't use slony as there is no network connection between
> the systems.
> 
> Please suggest some solution.
> 
> Thanks,
> Jyoti 
> 
> 
I guess you are triyng to avoid the 'pg_dump - save_to_floppy -
walk_to_db2_place - pg_restore' pattern. Well, can you save `pg_dump' in
some middle place? One place which machine1 and machine2 have access to?
If so, you can kind of automate the job using two programs, one (in the
master) who 'upload' (via ftp maybe, scp or whatever) in this middle
place, ando other in the slave who 'download' and process the file using
pg_restore.

HTH
Gerardo

On 2009-05-08, Jyoti Seth <jyotiseth2001@gmail.com> wrote:
> Hello,
>
> I have two databases db1 and db2 with the same database structure on
> different systems with no network connection. In the first system with the
> db1 database user updates the master data. At the end of every day, the user
> needs to take the backup of updated data of master tables on db1 and update
> the data on another system with db2 database.
>
> We can't use WAL as in this as we want to take incremental backup of few
> tables only and can't use slony as there is no network connection between
> the systems.
>
> Please suggest some solution.

some sort of diff?

dump the tables you are interested in in a known order

(perhaps use "copy from select .... order by .... " )

compare it with yesterdays 

ship the differences.

dump the table at the remote end
apply the patch
truncate the table and load the patched version.