Re: Adding variables for segment_size, wal_segment_size and block sizes

At 2008-07-03 16:36:02 +0200, mailings@oopsware.de wrote:
>
> Here's a patch for this.

I reviewed the patch, it basically looks fine. A few quibbles with the
provided documentation:

> +         Reports the number of pages which can be stored within a file segment.  
> +         The total physical size of a segment file in bytes can be determined by multiplying
> +         the <varname>block_size</varname> parameter with <varname>segment_size</varname>.

I would say:
   Reports the number of blocks/pages which can be stored within a file   segment. The total size of a segment file in
bytesis equal to the   <varname>segment_size</> multiplied by the <varname>block_size</>.
 

> +         Reports the size of a write ahead log disk block.  It is determined by the value
> +         of <literal>XLOG_BLCKSZ</> when building the server. The default
> +         value is 8192 bytes. <varname>wal_block_size</varname> influences the total physical
> +         size of a write ahead log segment. See <xref
> +         linkend="guc-wal-segment-size"> for more information.
> +        </para>

I'd change "write ahead log disk block" to "WAL disk block". How about
this:
   Reports the size of a WAL disk block, as determined by the value of   <literal>XLOG_BLCKSZ</> when compiling the
server.The default is   8192 bytes. <varname>wal_block_size</> influences the total size of   a WAL segment file. See
<xreflinkend="guc-wal-segment-size"> for   more information.
 

> +         Reports the number of pages within a write ahead log segment file. <varname>wal_segment_size</varname>
multipliedwith <varname>wal_block_size</varname> gives the total physical size of a write ahead
 
> +         log segment file in bytes.

Again, I'd say "WAL" here instead of "write ahead log", because the full
form is clumsy in context. How about this:
   Reports the number of pages in a WAL segment file. The total size of   a WAL segment file in bytes is equal to
<varname>wal_segment_size</>  multiplied by <varname>wal_block_size</>.
 

What do you think?

-- ams