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Thread: wal buffers documentation -errata

wal buffers documentation -errata

From
Dave Cramer
Date:
Currently says

Number of disk-page buffers allocated in shared memory for WAL data.  
The default is 8. The setting need only be large enough to hold the  
amount of WAL data generated by one typical transaction, since the  
data is written out to disk at every transaction commit. This  
parameter can only be set at server start.

However I just loaded up an 8.2.1 and the default is 32m

Dave

Re: wal buffers documentation -errata

From
Tom Lane
Date:
Dave Cramer <pg@fastcrypt.com> writes:
> However I just loaded up an 8.2.1 and the default is 32m

Then you changed it in postgresql.conf.  I get

$ psql
Welcome to psql 8.2.1, the PostgreSQL interactive terminal.

Type:  \copyright for distribution terms      \h for help with SQL commands      \? for help with psql commands      \g
orterminate with semicolon to execute query      \q to quit
 

regression=# show wal_buffers ;wal_buffers
-------------64kB
(1 row)

regression=#
        regards, tom lane

Re: wal buffers documentation -errata

From
Dave Cramer
Date:
Tom,

the point is that the documentation suggests that the default is 8

not 8MB, but 8, when in fact the defaults are now given in memory  
units not pages

Dave
On 11-Jan-07, at 10:09 AM, Tom Lane wrote:

> Dave Cramer <pg@fastcrypt.com> writes:
>> However I just loaded up an 8.2.1 and the default is 32m
>
> Then you changed it in postgresql.conf.  I get
>
> $ psql
> Welcome to psql 8.2.1, the PostgreSQL interactive terminal.
>
> Type:  \copyright for distribution terms
>        \h for help with SQL commands
>        \? for help with psql commands
>        \g or terminate with semicolon to execute query
>        \q to quit
>
> regression=# show wal_buffers ;
>  wal_buffers
> -------------
>  64kB
> (1 row)
>
> regression=#
>
>             regards, tom lane
>
> ---------------------------(end of  
> broadcast)---------------------------
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>        choose an index scan if your joining column's datatypes do not
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Re: wal buffers documentation -errata

From
Tom Lane
Date:
Dave Cramer <pg@fastcrypt.com> writes:
> the point is that the documentation suggests that the default is 8
> not 8MB, but 8, when in fact the defaults are now given in memory  
> units not pages

Oh, I thought you were complaining that the value was numerically wrong.

Perhaps we should convert the documentation to show the defaults in a
units-ified way, but if so it needs to be done consistently.  Most of
the entries seem not to have been changed; for example shared_buffers
is still described in blocks.
        regards, tom lane

Re: wal buffers documentation -errata

From
Dave Cramer
Date:
On 11-Jan-07, at 12:49 PM, Tom Lane wrote:

> Dave Cramer <pg@fastcrypt.com> writes:
>> the point is that the documentation suggests that the default is 8
>> not 8MB, but 8, when in fact the defaults are now given in memory
>> units not pages
>
> Oh, I thought you were complaining that the value was numerically  
> wrong.
>
> Perhaps we should convert the documentation to show the defaults in a
> units-ified way, but if so it needs to be done consistently.  Most of
> the entries seem not to have been changed; for example shared_buffers
> is still described in blocks.

Yes, everything is described in blocks, but in the configuration file  
everything (I've looked at so far) is specified in memory units.
While I appreciate the effort that went into making it somewhat  
easier to use memory units I can see this being very confusing for  
the average user.

I would suggest that the documentation needs to be consistent with  
the example configuration file installed by initdb

Dave
>
>             regards, tom lane
>
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> broadcast)---------------------------
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