Re: [HACKERS] Custom compression methods

On Fri, Dec 1, 2017 at 2:38 PM, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
> In mine, they define how things are accessed (i.e. more general than
> what you're thinking). We *currently* use them to store rows [in
> indexes], but there is no reason why we couldn't expand that.
>
> So we group access methods in "types"; the current type we have is for
> indexes, and methods in that type define how are indexes accessed. This
> new type would indicate how would values be compressed. I disagree that
> there is no parallel there.

+1.

> I'm trying to avoid pointless proliferation of narrowly defined DDL
> commands.

I also think that's an important goal.

> Yes, of course. I'm saying that the "datatype" property of a
> compression access method would be declared somewhere else, not in the
> TYPE clause of the CREATE ACCESS METHOD command. Perhaps it makes sense
> to declare that a certain compression access method is good only for a
> certain data type, and then you can put that in the options clause,
> "CREATE ACCESS METHOD hyperz TYPE COMPRESSION WITH (type = tsvector)".
> But many compression access methods would be general in nature and so
> could be used for many datatypes (say, snappy).
>
> To me it makes sense to say "let's create this method which is for data
> compression" (CREATE ACCESS METHOD hyperz TYPE COMPRESSION) followed by
> either "let's use this new compression method for the type tsvector"
> (ALTER TYPE tsvector SET COMPRESSION hyperz) or "let's use this new
> compression method for the column tc" (ALTER TABLE ALTER COLUMN tc SET
> COMPRESSION hyperz).

+1 to this, too.

--
Robert Haas
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