Re: TODO: Expose parser support for decoding unicode escape literals to user

Adrian Klaver-4 wrote
> On 05/15/2014 01:31 AM, Craig Ringer wrote:
>> Hi all
>>
>> I just noticed a Stack Overflow question
>> (http://stackoverflow.com/q/20124393/398670) where someone's asking how
>> to decode '\u0000` style escapes *stored in database text fields* into
>> properly encoded text strings.
>>
>> The parser supports this for escape-strings, and you can write E'\u011B'
>> to get 'ě' because of
>> http://postgresql.1045698.n5.nabble.com/Unicode-escapes-in-literals-td1992313.html.
>>
>> I don't see this exposed in a way that users can call directly, though.
>> 'decode(bytea, text)' has the 'escape' input, but it expects octal.
>>
>> It's possible to use PL/PgSQL's 'EXECUTE' to use the parser to do the
>> work, but that's downright awful.
>>
>> Am I missing something obvious, or is this something that'd be a good
>> new-developer TODO?
>>
>
> Not sure if this is what you want?:
>
> test=> SELECT quote_literal(E'test \u011B');
> quote_literal
> ---------------
> 'test ě'

Except the data is already in the database and there is no way to put an "E"
in front of a column name and cause PostgreSQL to process the escapes
embedded in the column's value in the same way it processes a literal.

WITH src (txt) AS ( VALUES ('A \u011B C') )
SELECT txt FROM src;

Hence the need for a function to perform the same process that the parser
performs when dealing with literals.

David J.

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