Re: UTF8 national character data type support WIP patch and list of open issues.

Attached is a patch that implements the first set of changes discussed
in this thread originally. They are:

(i) Implements NCHAR/NVARCHAR as distinct data types, not as synonyms so
that:
    - psql \d can display the user-specified data types.
    - pg_dump/pg_dumpall can output NCHAR/NVARCHAR columns as-is,
not as CHAR/VARCHAR.
    - Groundwork to implement additional features for NCHAR/NVARCHAR
in the future (For eg: separate encoding for nchar columns).
(ii) Support for NCHAR/NVARCHAR in ECPG
(iii) Documentation changes to reflect the new data type


Rgds,
Arul Shaji




>-----Original Message-----
>From: pgsql-hackers-owner@postgresql.org [mailto:pgsql-hackers-
>owner@postgresql.org] On Behalf Of MauMau
>
>From: "Greg Stark" <stark@mit.edu>
>> If it's not lossy then what's the point? From the client's point of
>> view it'll be functionally equivalent to text then.
>
>Sorry, what Tatsuo san suggested meant was "same or compatible", not
lossy.
>I quote the relevant part below.  This is enough for the use case I
mentioned
>in my previous mail several hours ago (actually, that is what Oracle
manual
>describes...).
>
>http://www.postgresql.org/message-id/20130920.085853.162891705483086415
1.t-
>ishii@sraoss.co.jp
>
>[Excerpt]
>----------------------------------------
>What about limiting to use NCHAR with a database which has same
encoding or
>"compatible" encoding (on which the encoding conversion is defined)?
This way,
>NCHAR text can be automatically converted from NCHAR to the database
encoding
>in the server side thus we can treat NCHAR exactly same as CHAR
afterward.  I
>suppose what encoding is used for NCHAR should be defined in initdb
time or
>creation of the database (if we allow this, we need to add a new column
to know
>what encoding is used for NCHAR).
>
>For example, "CREATE TABLE t1(t NCHAR(10))" will succeed if NCHAR is
>UTF-8 and database encoding is UTF-8. Even succeed if NCHAR is
SHIFT-JIS and
>database encoding is UTF-8 because there is a conversion between UTF-8
and
>SHIFT-JIS. However will not succeed if NCHAR is SHIFT-JIS and database
encoding
>is ISO-8859-1 because there's no conversion between them.
>----------------------------------------
>
>
>Regards
>MauMau
>
>
>
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