what is the solution like oracle DB's datafile

Hi,

On Sun, Jan 30, 2022 at 05:15:33AM +0700, Yudianto Prasetyo wrote:

I'm confused when I have 2 HDD. HDD 1 is used to install the OS and
postgresql database. when HDD 1 is full. how to increase the capacity of
postgresql database with HDD 2 (without RAID system)?

is there any other way like oracle DB's "add datafile" which can be used to
add capacity to another HDD?

I don't know how those datafiles are working, but with postgres the solution is
to create additional tablespaces pointing to the new drives, see
https://www.postgresql.org/docs/current/sql-createtablespace.html.

Note that a single non-partitioned table can only exist on a single tablespace,
so if you have a gigantic table that's becoming bigger than you disk, the
solution might be to partition it and store different partitions on different
tablespaces.

Hi,

Please keep the list in copy and don't top post here:
https://wiki.postgresql.org/wiki/Mailing_Lists#Email_etiquette_mechanics

On Sun, Jan 30, 2022 at 08:18:15PM +0700, Yudianto Prasetyo wrote:

what is the function of adding a new tablespace if we will only fill data
in table color and HDD1 is full? can't we fill the data in table color
because it still refers to the old tablespace ( small_data on HDD 1 not in
the new tablespace on HDD 2 )

You can move some of the tables and/or indexes on the new tablespace to free
some space on the old one, see e.g.:

- ALTER TABLE ... SET TABLESPACE: https://www.postgresql.org/docs/current/sql-altertable.html
- ALTER INDEX ... SET TABLESPACE: https://www.postgresql.org/docs/current/sql-alterindex.html

I already asked you once to keep the list in copy. Don't expect me to reply if
your next email is still addressed to me only.

On Sun, Jan 30, 2022 at 08:36:50PM +0700, Yudianto Prasetyo wrote:

yes of course it can be done. but it is very inconvenient when the database
is still running and most importantly it is not practical when having to
move some objects to another tablespace. And this will also happen again
when HDD 1 will be full again with data entry by other objects on HDD 1.

Then fix the problem at the operating system level. On GNU/Linux you can use
for instance LVM to get more flexibility. With it you can easily increase your
logical volume space without any interruption, and the database will only see a
regular disk that magically became bigger. There is probably something similar
on the operating system you're using. Of course, if you don't already use
something like that, you will need some maintenance window to move all data on
logical volumes.

hello,

thanks for other solutions in the operating system section. LVM, RAID is
indeed one solution to this problem.

Maybe there is another solution in the postgresql database like the
datafile in oracle DB?

thank you,
Yours faithfully

yudianto

On Sun, Jan 30, 2022 at 8:44 PM Julien Rouhaud <rjuju123@gmail.com> wrote:

On Sun, Jan 30, 2022 at 08:51:02PM +0700, Yudianto Prasetyo wrote:

thanks for other solutions in the operating system section. LVM, RAID is
indeed one solution to this problem.

Maybe there is another solution in the postgresql database like the
datafile in oracle DB?

As I said I don't know how datafiles in oracle are working. All you have on
postgres is tablespaces, default tablespaces and moving relations from one
tablespaces to another.

In general, postgres doesn't try to reimplement solution to problems that are
nicely solved at the operating system level, so if those datafile are
reimplementing something similar to LVM, then no postgres doesn't have
something like that and probably doesn't want it.

Hello,

dafafile this oracle like this example. can be added to another hdd.

ALTER TABLESPACE lmtbsb
ADD DATAFILE '/u02/oracle/data/lmtbsb02.dbf' SIZE 1M;

ALTER TABLESPACE lmtbsb
ADD DATAFILE '/u03/oracle/data/lmtbsb02.dbf' SIZE 1M;

ALTER TABLESPACE lmtbsb
ADD DATAFILE 'e:\data\lmtbsb02.dbf' SIZE 1M;

ALTER TABLESPACE lmtbsb
ADD DATAFILE 'f:\data2\lmtbsb02.dbf' SIZE 1M;

i understand about that LVM solution. it is true that using this method can
be done. I'm just asking for a solution at the database level.

thank you
Yours faithfully

yudianto

On Sun, Jan 30, 2022 at 9:17 PM Julien Rouhaud <rjuju123@gmail.com> wrote:

On 1/29/22 17:15, Yudianto Prasetyo wrote:

Hello,

I want to ask why postgresql doesn't create a datafile like it has oracle?

I'm confused when I have 2 HDD. HDD 1 is used to install the OS and
postgresql database. when HDD 1 is full. how to increase the capacity
of postgresql database with HDD 2 (without RAID system)?

is there any other way like oracle DB's "add datafile" which can be
used to add capacity to another HDD?

I'm sorry if it says comparing with Oracle DB, but in essence I'm just
looking for a solution to the problem above.

Thank You
Yours faithfully

Yudianto

Number one, Postgres tables are files. Tablespaces are directories which
reside in file systems, In Oracle, tables are sets of blocks within data
files that tablespace is comprised of. That is a profound difference. In
Oracle, we are using direct IO to bypass the OS cache and only use SGA
("System Global Area") for caching data blocks. In Postgres, we are
caching blocks from the files in OS cache which is essentially the free
memory.

When translated to Postgres, your question reads: how to add space to
file system? That depends on the file system and volume manager. If
you're using brtfs or zfs (hopefully not) then your file sysems are also
volume managers, If you're using LVM with xfs (my combination), then you
can add space to your volume and extend the xfs file system. I have also
tried using Oracle ASM as volume manager and use ACFS as the file
system. The result was very nice, roughly the same as with LVM. However,
the installation of ASM is rather complex and since PostgreSQL cannot be
clustered, there is no justification for doing that.

--
Mladen Gogala
Database Consultant
Tel: (347) 321-1217
https://dbwhisperer.wordpress.com

ne 30. 1. 2022 v 18:13 odesílatel Yudianto Prasetyo
<mr.yudianto@gmail.com> napsal:

Hello,

dafafile this oracle like this example. can be added to another hdd.

ALTER TABLESPACE lmtbsb
ADD DATAFILE '/u02/oracle/data/lmtbsb02.dbf' SIZE 1M;

ALTER TABLESPACE lmtbsb
ADD DATAFILE '/u03/oracle/data/lmtbsb02.dbf' SIZE 1M;

ALTER TABLESPACE lmtbsb
ADD DATAFILE 'e:\data\lmtbsb02.dbf' SIZE 1M;

ALTER TABLESPACE lmtbsb
ADD DATAFILE 'f:\data2\lmtbsb02.dbf' SIZE 1M;

i understand about that LVM solution. it is true that using this method can be done. I'm just asking for a solution at the database level.

Per my understanding, there is no exactly the same feature in
PostgreSQL itself. As mentioned before, it is most likely by design.

hello,

thanks for all the solutions. I don't think there is a solution like Oracle
DB's datafile in postgresql. LVM is probably the best way if using Linux OS.

Thank You
Yours faithfully

yudianto

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On Mon, Jan 31, 2022 at 12:19 AM Josef Šimánek <josef.simanek@gmail.com>
wrote:

On Sun, 2022-01-30 at 05:15 +0700, Yudianto Prasetyo wrote:

I want to ask why postgresql doesn't create a datafile like it has oracle?

I'm confused when I have 2 HDD. HDD 1 is used to install the OS and postgresql database.
when HDD 1 is full. how to increase the capacity of postgresql database with HDD 2 (without RAID system)?

is there any other way like oracle DB's "add datafile" which can be used to add capacity to another HDD?

The difference between Oracle and PostgreSQL here is that Oracle implemented its
own file system and volume manager, while PostgreSQL uses the facilities provided
by the operating system.

The correspondence is not perfect, but you can compare an Oracle tablespace to
a logical volume with a file system and a datafile to a physical volume.

So to get the same thing in PostgreSQL, you have to interact with the operating
system: add a new physical volume to the logical volume where your database
resides and extend the file system.

To answer the question "why", here are two points:

- PostgreSQL does not have the (wo)manpower to re-invent the wheel on everything,
so we tend to use existing facilities

- Oracle was developed earlier, and one can argue that in those days file systems
were not so great, so there was more need to write your own

Yours,
Laurenz Albe
--
Cybertec | https://www.cybertec-postgresql.com

hello,

thanks for the logical answer. it is true that there is a very big
difference between open source and commercial DB. but I'm grateful to be
able to use postgresql which is quite reliable.

thank you
Yours faithfully

yudianto

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On Mon, Jan 31, 2022 at 12:10 PM Laurenz Albe <laurenz.albe@cybertec.at>
wrote:

<laurenz.albe@cybertec.at> wrote:

- Oracle was developed earlier, and one can argue that in those days file systems
were not so great, so there was more need to write your own

Correct me if I'm wrong, but didn't Postgres (or Ingres upon which it's based) development start in the early-to-mid 70's and Oracle's only in the late 70's - early 80's?

[1]: https://en.wikipedia.org/wiki/Ingres_(database)#Early_history
[2]: https://en.wikipedia.org/wiki/PostgreSQL#History

E.

Le mar. 27 déc. 2022 à 11:37, Eagna <eagna@protonmail.com> a écrit :

<laurenz.albe@cybertec.at> wrote:

- Oracle was developed earlier, and one can argue that in those days

file systems

were not so great, so there was more need to write your own

Correct me if I'm wrong, but didn't Postgres (or Ingres upon which it's
based) development start in the early-to-mid 70's and Oracle's only in the
late 70's - early 80's?

[1] https://en.wikipedia.org/wiki/Ingres_(database)#Early_history
[2] https://en.wikipedia.org/wiki/PostgreSQL#History

" The origins of PostgreSQL date back to 1986 as part of the POSTGRES
project at the University of California at Berkeley and has more than 35
years of active development on the core platform." (
https://www.postgresql.org/about/)

--
Guillaume.