(2013/01/07 22:36), Greg Stark wrote:
> On Mon, Jan 7, 2013 at 10:21 AM, John R Pierce<pierce(at)hogranch(dot)com> wrote:
>> On 1/7/2013 2:05 AM, Andres Freund wrote:
>>> I think there should be enough bits available in the toast pointer to
>>> indicate the type of compression. I seem to remember somebody even
>>> posting a patch to that effect?
>>> I agree that it's probably too late in the 9.3 cycle to start with this.
>> so an upgraded database would have old toasted values in the old compression
>> format, and new toasted values in the new format in an existing table?
>> that's kind of ugly.
> I haven't looked at the patch. It's not obvious to me from the
> description that the output isn't backwards compatible. The way the LZ
> toast compression works the output is self-describing. There are many
> different outputs that would decompress to the same thing and the
> compressing code can choose how hard to look for earlier matches and
> when to just copy bytes wholesale but the decompression will work
My patch is not backwards compatible, so we need some features
to switch these old and new disk formats.
I think the discussion below is helpful in this use.
That is, PGLZ_Header is used as this purpose.
NTT Cyber Communications Laboratory Group
Software Innovation Center
(Open Source Software Center)
Tel: +81-3-5860-5057 Fax: +81-3-5463-5490
In response to
pgsql-hackers by date
|Next:||From: Magnus Hagander||Date: 2013-01-08 09:32:40|
|Subject: Re: PL/Python result object str handler|
|Previous:||From: Pavan Deolasee||Date: 2013-01-08 09:11:54|
|Subject: Re: lazy_vacuum_heap()'s removal of HEAPTUPLE_DEAD tuples|