On Tue, Jul 21, 2015 at 9:23 AM, Robert Haas <robertmh...@gmail.com> wrote:
> rhaas=# create unique index on foo (a collate "C"); > CREATE INDEX > rhaas=# alter table foo add primary key using index foo_a_idx; > ALTER TABLE > > Now dump and restore this database. Then: > > Notice that the collation specifier is gone. Oops. > The intent of the 'USING INDEX' feature was to work around the problem that PRIMARY KEY indexes cannot be reindexed concurrently to reduce bloat. Considering that the feature doesn't work [1] (at least as shown in example in the docs [2]) if there are any foreign keys referencing the table, there's scope for improvement. There was proposal to support reindexing the primary key index, but I am not sure where that stands. If that's already in, or soon to be in core, we may put a deprecation notice around USING INDEX. OTOH, if reindexing PKeys is too difficult, we may want to support index-replacement via a top-level ALTER TABLE subcommand that works in CONCURRENT mode, and not recommend the method shown in the docs (i.e deprecate the USING INDEX syntax). [1]: The DROP CONSTRAINT part of the command fails if there are any FKeys pointing to this table. [2]: http://www.postgresql.org/docs/9.4/static/sql-altertable.html -- Gurjeet Singh http://gurjeet.singh.im/
