Re: Yet another fast GiST build

Thanks Darafei!

> 9 сент. 2020 г., в 12:05, Darafei Komяpa Praliaskouski <me(at)komzpa(dot)net> написал(а):
>
> > How does the 'sortsupport' routine interact with 'compress'/'decompress'? Which representation is passed to the comparator routine: the original value from the table, the compressed representation, or the decompressed representation? Do the comparetup_index_btree() and readtup_index() routines agree with that?
>
> Currently we pass compressed values, which seems not very good.
> But there was a request from PostGIS maintainers to pass values before decompression.
> Darafei, please, correct me if I'm wrong. Also can you please provide link on PostGIS B-tree sorting functions?
>
> We were expecting to reuse btree opclass for this thing. This way btree_gist extension will become a lot thinner. :)

I think if we aim at reusing B-tree sort support functions we have to pass uncompressed values. They can be a lot bigger and slower in case of PostGIS. We will be sorting actual geometries instead of MBRs.

In my view it's better to implement GiST-specific sort support in btree_gist, rather than trying to reuse existing sort supports.

Best regards, Andrey Borodin.