Re: Proposal - Support for National Characters functionality

From: "Arulappan, Arul Shaji" <arul(at)fast(dot)au(dot)fujitsu(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
Cc: "Boguk, Maksym" <maksymb(at)fast(dot)au(dot)fujitsu(dot)com>, Tatsuo Ishii <ishii(at)postgresql(dot)org>, Robert Haas <robertmhaas(at)gmail(dot)com>, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, Peter Eisentraut <peter_e(at)gmx(dot)net>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Proposal - Support for National Characters functionality
Date: 2013-08-01 01:03:58
Message-ID: 3AFB102B67FAEE48874E0607386DF4210DD2CFE0@SYDExchTmp.au.fjanz.com
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> From: Tom Lane [mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us]
>
> Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> writes:
> > Also, as far as I understand what we want to control here is the
> > encoding that the strings are in (the mapping of bytes to
characters),
> > not the collation (the way a set of strings are ordered). So it
> > doesn't make sense to set the NATIONAL CHARACTER option using the
> > COLLATE keyword.
>
> My thought is that we should simply ignore the NATIONAL CHARACTER
syntax,
> which is not the first nor the last brain-damaged feature design in
the SQL
> standard. It's basically useless for what we want because there's
noplace to
> specify which encoding you mean. Instead, let's consider that COLLATE
can
> define not only the collation but also the encoding of a string datum.

Yes, don't have a problem with this. If I understand you correctly, this
will be simpler syntax wise, but still get nchar/nvarchar data types
into a table, in different encoding from the rest of the table.

>
> There's still the problem of how do you get a string of a nondefault
encoding
> into the database in the first place.

Yes, that is the bulk of the work. Will need change in a whole lot of
places.

Is a step-by-step approach worth exploring ? Something similar to:

Step 1: Support nchar/nvarchar data types. Restrict them only to UTF-8
databases to begin with.
Step 2: Support multiple encodings in a database. Remove the restriction
imposed in step1.

Rgds,
Arul Shaji

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