Re: pgsql: Add function to import operating system collations

I wrote:
> running bootstrap script ... ok
> performing post-bootstrap initialization ... 2017-01-18 09:49:45.019 EST [25919] FATAL: collation "aa_ER(at)saaho" for encoding "UTF8" already exists
> 2017-01-18 09:49:45.019 EST [25919] STATEMENT: SELECT pg_import_system_collations(if_not_exists => false, schema => 'pg_catalog');

As a stopgap so I could get some work done, I did

- PG_CMD_PUTS("SELECT pg_import_system_collations(if_not_exists => false, schema => 'pg_catalog');\n\n");
+ PG_CMD_PUTS("SELECT pg_import_system_collations(if_not_exists => true, schema => 'pg_catalog');\n\n");

and what I now see in pg_collation is

regression=# select * from pg_collation where collname like 'aa_ER%';
collname | collnamespace | collowner | collencoding | collcollate | collctype
------------------+---------------+-----------+--------------+------------------+------------------
aa_ER | 11 | 10 | 6 | aa_ER | aa_ER
aa_ER.utf8 | 11 | 10 | 6 | aa_ER.utf8 | aa_ER.utf8
aa_ER(dot)utf8(at)saaho | 11 | 10 | 6 | aa_ER(dot)utf8(at)saaho | aa_ER(dot)utf8(at)saaho
aa_ER(at)saaho | 11 | 10 | 6 | aa_ER(dot)utf8(at)saaho | aa_ER(dot)utf8(at)saaho
(4 rows)

Maybe an appropriate fix would be to ignore collations whose names aren't
equal to what we get for collcollate/collctype. Presumably the latter
are getting canonicalized somehow.

regards, tom lane