Обсуждение: pg_dump consistency.

Hi all,

I have been reading but cannot find this particular bit of info.

I need to guarantee to my customer that the pg_dump is consistent. I
couldn't guarantee consistency if the pg_dump is run while the db is
on-line, and we cannot take the db off-line to do backups.

So, can anyone tell me
1. IF pg_dump is consistent (without taking the db offline),
2. if so, how does it do it?
3. if not, how can we get consistent backups without taking the db
offline?

Thanks.

Marc Wrubleski

Marc Wrubleski wrote:
  >Hi all,
  >
  >I have been reading but cannot find this particular bit of info.
  >
  >I need to guarantee to my customer that the pg_dump is consistent. I
  >couldn't guarantee consistency if the pg_dump is run while the db is
  >on-line, and we cannot take the db off-line to do backups.
  >
  >So, can anyone tell me
  >1. IF pg_dump is consistent (without taking the db offline),

Yes

  >2. if so, how does it do it?

As with any other SQL query, pg_dump ignores any transaction started
or completed after its own start.

--
Oliver Elphick                                Oliver.Elphick@lfix.co.uk
Isle of Wight                              http://www.lfix.co.uk/oliver
PGP: 1024R/32B8FAA1: 97 EA 1D 47 72 3F 28 47  6B 7E 39 CC 56 E4 C1 47
GPG: 1024D/3E1D0C1C: CA12 09E0 E8D5 8870 5839  932A 614D 4C34 3E1D 0C1C
                 ========================================
     "Finally, brethren, whatsoever things are true,
      whatsoever things are honest, whatsoever things are
      just, whatsoever things are pure, whatsoever things
      are lovely, whatsoever things are of good report; if
      there be any virtue, and if there be any praise, think
      on these things."    Philippians 4:8

hi Marc
If u log all the queries which get executed when a dump takes place u
will find that the pg_dump process first sets the transaction isolation
level to serializable..

So i guess all the state of the database dumped is consistent with a
point in time..

Hope this helps
Anand
On Mon, Apr 09, 2001 at 03:20:03PM -0600, Marc Wrubleski wrote:
>Hi all,
>
>I have been reading but cannot find this particular bit of info.
>
>I need to guarantee to my customer that the pg_dump is consistent. I
>couldn't guarantee consistency if the pg_dump is run while the db is
>on-line, and we cannot take the db off-line to do backups.
>
>So, can anyone tell me
>1. IF pg_dump is consistent (without taking the db offline),
>2. if so, how does it do it?
>3. if not, how can we get consistent backups without taking the db
>offline?
>
>Thanks.
>
>Marc Wrubleski
>
>
>---------------------------(end of broadcast)---------------------------
>TIP 2: you can get off all lists at once with the unregister command
>    (send "unregister YourEmailAddressHere" to majordomo@postgresql.org)