Re: [HACKERS] Custom compression methods

On 2021-Mar-19, Robert Haas wrote:

> On Fri, Mar 19, 2021 at 10:11 AM Dilip Kumar <dilipbalaut@gmail.com> wrote:
> > Also added a test case for vacuum full to recompress the data.
> 
> I committed the core patch (0003) with a bit more editing.  Let's see
> what the buildfarm thinks.

I updated the coverage script to use --with-lz4; results are updated.
While eyeballing the results I noticed this bit in
lz4_decompress_datum_slice():

+   /* slice decompression not supported prior to 1.8.3 */
+   if (LZ4_versionNumber() < 10803)
+       return lz4_decompress_datum(value);

which I read as returning the complete decompressed datum if slice
decompression is not supported.  I thought that was a bug, but looking
at the caller I realize that this isn't really a problem, since it's
detoast_attr_slice's responsibility to slice the result further -- no
bug, it's just wasteful.  I suggest to add comments to this effect,
perhaps as the attached (feel free to reword, I think mine is awkward.)

-- 
Álvaro Herrera                            39°49'30"S 73°17'W
Si no sabes adonde vas, es muy probable que acabes en otra parte.