Re: Adding variables for segment_size, wal_segment_size and block sizes

At 2008-07-03 16:36:02 +0200, mailings(at)oopsware(dot)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 bytes is 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 <xref linkend="guc-wal-segment-size"> for
more information.

> + Reports the number of pages within a write ahead log segment file. <varname>wal_segment_size</varname> multiplied with <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