Thread: Function to total reset a schema

Hi all,
I need to write a function that totally empty a schema.

So I have written a TRUNCATE statement for each table and set to 0 each 
sequence.
Btw, it could be good to execute a vacuum statement on each table, but 
from within the function this is not allowed.

Is there a way to obtain the same result in another way (without using 
the vacuum)?

Thanks

On Sun, May 29, 2011 at 1:38 AM, Surfing <onlinesurfing@gmail.com> wrote:
> Hi all,
> I need to write a function that totally empty a schema.
>
> So I have written a TRUNCATE statement for each table and set to 0 each
> sequence.
> Btw, it could be good to execute a vacuum statement on each table, but from
> within the function this is not allowed.

You shouldn't need to vacuum truncated tables, as they're basically at
a lower level just wiped out and replaced by a new empty file / table.Same goes for the indexes I believe.

Surfing wrote on 29.05.2011 09:38:
> Hi all,
> I need to write a function that totally empty a schema.
>
> So I have written a TRUNCATE statement for each table and set to 0 each sequence.
> Btw, it could be good to execute a vacuum statement on each table, but from within the function this is not allowed.
>
> Is there a way to obtain the same result in another way (without using the vacuum)?
>

If you are only using a single schema in your database, you could create an empty database with all your tables that
youthen use as the template database when creating a new one:
 

Then each time you want to reset your schema (=database) you do a

drop database real_database;
create database real_database template template_database;

Then you don't need to adjust your "reset" script if your database changes (you only maintain the template database
usingyour SQL scripts)
 

Thomas

I have two schemas, so I can't do that ...
@ Scott. You are totally right ... I have just read this on the 
documentation:

"TRUNCATE quickly removes all rows from a set of tables. It has the same 
effect as an unqualified
DELETE on each table, but since it does not actually scan the tables it 
is faster. Furthermore, it reclaims
disk space immediately, rather than requiring a subsequent VACUUM 
operation. This is most useful on
large tables."

So the VACUUM should not really be necessary..thanks.

Il 29/05/2011 09:54, Thomas Kellerer ha scritto:
> Surfing wrote on 29.05.2011 09:38:
>> Hi all,
>> I need to write a function that totally empty a schema.
>>
>> So I have written a TRUNCATE statement for each table and set to 0 
>> each sequence.
>> Btw, it could be good to execute a vacuum statement on each table, 
>> but from within the function this is not allowed.
>>
>> Is there a way to obtain the same result in another way (without 
>> using the vacuum)?
>>
>
> If you are only using a single schema in your database, you could 
> create an empty database with all your tables that you then use as the 
> template database when creating a new one:
>
> Then each time you want to reset your schema (=database) you do a
>
> drop database real_database;
> create database real_database template template_database;
>
> Then you don't need to adjust your "reset" script if your database 
> changes (you only maintain the template database using your SQL scripts)
>
> Thomas
>
>

I would hope you have readily at hand the ddl for the schema in 
question.  Then it's simply a matter of drop schema <name> cascade and 
re-run you ddl scripts.

Surfing wrote:
> Hi all,
> I need to write a function that totally empty a schema.
>
> So I have written a TRUNCATE statement for each table and set to 0 
> each sequence.
> Btw, it could be good to execute a vacuum statement on each table, but 
> from within the function this is not allowed.
>
> Is there a way to obtain the same result in another way (without using 
> the vacuum)?
>
> Thanks
>
>