Re: Custom index access method for primary keys

Fabian Lindfors <fabian@flapplabs.se> writes:
> Hi! I’m working on an index access method that I intend to be
> generic and to replace btree for my specific use case. I noticed
> though that it doesn’t seem to be possible to specify an access
> method when creating a new table and using PRIMARY KEY.

There's some work going on right now to remove the core code's
assumptions that only btree can handle unique/pkey constraints
and sorting [1].  I'm not sure if it'll be entirely complete for
v18 but the goalposts have been moved quite far.  I think you can
probably expect to be able to do

    CREATE TABLE mytable ...;
    CREATE UNIQUE INDEX myindex ON mytable USING myam (...);
    ALTER TABLE mytable ADD PRIMARY KEY USING INDEX myindex;

It doesn't look like we yet allow direct "USING myam" in
PRIMARY KEY, but sooner or later we might get to that.

            regards, tom lane

[1] https://www.postgresql.org/message-id/flat/E72EAA49-354D-4C2E-8EB9-255197F55330%40enterprisedb.com