Refactor get_collation_current_version().

The code paths for three different OSes finished up with three different
ways of excluding C[.xxx] and POSIX from consideration.  Merge them.

Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/20210117215940.GE8560%40telsasoft.com

diff --git a/src/backend/utils/adt/pg_locale.c b/src/backend/utils/adt/pg_locale.c
index 2e4c6e9a263917480dfe94a898c54792dd3ca567..df1f36132d38a8f6115b5782345bb75112ff5fa8 100644 (file)
--- a/src/backend/utils/adt/pg_locale.c
+++ b/src/backend/utils/adt/pg_locale.c
@@ -1636,37 +1636,17 @@ get_collation_current_version(char collprovider, const char *collcollate)
        }
        else
 #endif
-       if (collprovider == COLLPROVIDER_LIBC)
+       if (collprovider == COLLPROVIDER_LIBC &&
+               pg_strcasecmp("C", collcollate) != 0 &&
+               pg_strncasecmp("C.", collcollate, 2) != 0 &&
+               pg_strcasecmp("POSIX", collcollate) != 0)
        {
 #if defined(__GLIBC__)
-               char       *copy = pstrdup(collcollate);
-               char       *copy_suffix = strstr(copy, ".");
-               bool            need_version = true;
-
-               /*
-                * Check for names like C.UTF-8 by chopping off the encoding suffix on
-                * our temporary copy, so we can skip the version.
-                */
-               if (copy_suffix)
-                       *copy_suffix = '\0';
-               if (pg_strcasecmp("c", copy) == 0 ||
-                       pg_strcasecmp("posix", copy) == 0)
-                       need_version = false;
-               pfree(copy);
-               if (!need_version)
-                       return NULL;
-
                /* Use the glibc version because we don't have anything better. */
                collversion = pstrdup(gnu_get_libc_version());
 #elif defined(LC_VERSION_MASK)
                locale_t    loc;
 
-               /* C[.encoding] and POSIX never change. */
-               if (strcmp("C", collcollate) == 0 ||
-                       strncmp("C.", collcollate, 2) == 0 ||
-                       strcmp("POSIX", collcollate) == 0)
-                       return NULL;
-
                /* Look up FreeBSD collation version. */
                loc = newlocale(LC_COLLATE, collcollate, NULL);
                if (loc)
@@ -1687,12 +1667,6 @@ get_collation_current_version(char collprovider, const char *collcollate)
                NLSVERSIONINFOEX version = {sizeof(NLSVERSIONINFOEX)};
                WCHAR           wide_collcollate[LOCALE_NAME_MAX_LENGTH];
 
-               /* These would be invalid arguments, but have no version. */
-               if (pg_strcasecmp("c", collcollate) == 0 ||
-                       pg_strcasecmp("posix", collcollate) == 0)
-                       return NULL;
-
-               /* For all other names, ask the OS. */
                MultiByteToWideChar(CP_ACP, 0, collcollate, -1, wide_collcollate,
                                                        LOCALE_NAME_MAX_LENGTH);
                if (!GetNLSVersionEx(COMPARE_STRING, wide_collcollate, &version))