Re: patch: function xmltable
| От | Pavel Stehule |
|---|---|
| Тема | Re: patch: function xmltable |
| Дата | |
| Msg-id | CAFj8pRDsBeTRR3xDXbHnR19ifCRrnq7SDwM=b-i_=5mbhOzTVA@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: patch: function xmltable (Craig Ringer <craig@2ndquadrant.com>) |
| Список | pgsql-hackers |
2016-09-12 6:36 GMT+02:00 Craig Ringer <craig@2ndquadrant.com>:
On 12 September 2016 at 12:28, Craig Ringer <craig@2ndquadrant.com> wrote:
>> I'll take a closer read-through shortly.
>DEFAULT
> isn't a normal literal, it's an xpath expression evaluated at the same
> time as the rowexpression.
Sorry for the spam, but turns out that's not the case as implemented
here. The docs you referenced say it should be an xpath expression,
but the implementation here is of a literal value, and examples
elsewhere on the Internet show a literal value. Unclear if the
referenced docs are wrong or what and I don't have anything to test
with.
It is not spam. The previous comment was not correct. DEFAULT is a expression - result of this expression is used, when data is missing.
In standard, and some others implementation, this is literal only. It is similar to DEFAULT clause in CREATE STATEMENT. Postgres allows expression there. Usually Postgres allows expressions everywhere when it has sense, and when it is allowed by bizon parser.
Feel free to fix/trim the DEFAULT related changes in above docs patch as needed.
Also, tests/docs should probably cover what happens when PATH matches
more than one element, i.e. produces a list of more than one match.
--
Craig Ringer http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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