Avoid conflicts with collation aliases generated by stripping.

This resulted in failures depending on the order of "locale -a" output.
The original coding in initdb sorted the results, but that should be
unnecessary as long as "locale -a" doesn't print duplicate names.  The
original entries will then all be non-dups, and while we might generate
duplicate aliases by stripping, they should be for different encodings and
thus not conflict.  Even if the latter assumption fails somehow, it won't
be fatal because we're using if_not_exists mode for the aliases.

Discussion: https://postgr.es/m/26116.1484751196%40sss.pgh.pa.us

diff --git a/src/backend/commands/collationcmds.c b/src/backend/commands/collationcmds.c
index 5cb3e2bb282e39bd453ad0dbff15f0cd2e3d5d72..71b21bf0d209de8c71e9d1a482735ed3d1edc6e6 100644 (file)
--- a/src/backend/commands/collationcmds.c
+++ b/src/backend/commands/collationcmds.c
@@ -224,11 +224,17 @@ pg_import_system_collations(PG_FUNCTION_ARGS)
 {
 #if defined(HAVE_LOCALE_T) && !defined(WIN32)
        bool            if_not_exists = PG_GETARG_BOOL(0);
-       Oid         nspid = PG_GETARG_OID(1);
+       Oid                     nspid = PG_GETARG_OID(1);
 
        FILE       *locale_a_handle;
        char            localebuf[NAMEDATALEN]; /* we assume ASCII so this is fine */
        int                     count = 0;
+       List       *aliaslist = NIL;
+       List       *localelist = NIL;
+       List       *enclist = NIL;
+       ListCell   *lca,
+                          *lcl,
+                          *lce;
 #endif
 
        if (!superuser())
@@ -306,26 +312,36 @@ pg_import_system_collations(PG_FUNCTION_ARGS)
                 * ease of use.  Note that collation names are unique per encoding
                 * only, so this doesn't clash with "en_US" for LATIN1, say.
                 *
-                * This always runs in "if not exists" mode, to skip aliases that
-                * conflict with an existing locale name for the same encoding.  For
-                * example, "br_FR.iso88591" is normalized to "br_FR", both for
-                * encoding LATIN1.  But the unnormalized locale "br_FR" already
-                * exists for LATIN1.
+                * However, it might conflict with a name we'll see later in the
+                * "locale -a" output.  So save up the aliases and try to add them
+                * after we've read all the output.
                 */
                if (normalize_locale_name(alias, localebuf))
                {
-                       CollationCreate(alias, nspid, GetUserId(), enc,
-                                                       localebuf, localebuf, true);
-                       CommandCounterIncrement();
+                       aliaslist = lappend(aliaslist, pstrdup(alias));
+                       localelist = lappend(localelist, pstrdup(localebuf));
+                       enclist = lappend_int(enclist, enc);
                }
        }
 
        ClosePipeStream(locale_a_handle);
 
+       /* Now try to add any aliases we created */
+       forthree(lca, aliaslist, lcl, localelist, lce, enclist)
+       {
+               char       *alias = (char *) lfirst(lca);
+               char       *locale = (char *) lfirst(lcl);
+               int                     enc = lfirst_int(lce);
+
+               CollationCreate(alias, nspid, GetUserId(), enc,
+                                               locale, locale, true);
+               CommandCounterIncrement();
+       }
+
        if (count == 0)
                ereport(ERROR,
                                (errmsg("no usable system locales were found")));
-#endif /* not HAVE_LOCALE_T && not WIN32 */
+#endif   /* not HAVE_LOCALE_T && not WIN32 */
 
        PG_RETURN_VOID();
 }