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Create an explicit concept of collations that work for any encoding.

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Use collencoding = -1 to represent such a collation in pg_collation.
We need this to make the "default" entry work sanely, and a later
patch will fix the C/POSIX entries to be represented this way instead
of duplicating them across all encodings.  All lookup operations now
search first for an entry that's database-encoding-specific, and then
for the same name with collencoding = -1.

Also some incidental code cleanup in collationcmds.c and pg_collation.c.
This commit is contained in:
Tom Lane
2011-03-11 13:20:11 -05:00
parent ac435a79c8
commit e3c732a85c
9 changed files with 158 additions and 84 deletions
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12
doc/src/sgml/catalogs.sgml
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@@ -2132,7 +2132,8 @@
<entry><structfield>collencoding</structfield></entry>
<entry><type>int4</type></entry>
<entry></entry>
<entry>Encoding to which the collation is applicable</entry>
<entry>Encoding in which the collation is applicable, or -1 if it
works for any encoding</entry>
</row>
<row>
@@ -2157,12 +2158,13 @@
<structfield>collencoding</>, <structfield>collnamespace</>) not just
(<structfield>collname</>, <structfield>collnamespace</>).
<productname>PostgreSQL</productname> generally ignores all
collations not belonging to the current database's encoding; therefore
it is sufficient to use a qualified SQL name
collations that do not have <structfield>collencoding</> equal to
either the current database's encoding or -1, and creation of new
entries matching an entry with <structfield>collencoding</> = -1
is forbidden. Therefore it is sufficient to use a qualified SQL name
(<replaceable>schema</>.<replaceable>name</>) to identify a collation,
even though this is not unique according to the catalog definition.
The current database's encoding is automatically used as an additional
lookup key. The reason for defining the catalog this way is that
The reason for defining the catalog this way is that
<application>initdb</> fills it in at cluster initialization time with
entries for all locales available on the system, so it must be able to
hold entries for all encodings that might ever be used in the cluster.