Re: [COMMITTERS] 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@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.utf8@saaho |            11 |        10 |            6 | aa_ER.utf8@saaho | aa_ER.utf8@saaho
 aa_ER@saaho      |            11 |        10 |            6 | aa_ER.utf8@saaho | aa_ER.utf8@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