Re: PostgreSQL vs SQL Standard

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От	Brad DeJong
Тема	Re: PostgreSQL vs SQL Standard
Дата	30 июня 2018 г. 22:42:44
Msg-id	CAJnrtnxrV_Nbfs1SZD6CmfB0dfAtGfKGLmLOED02M47RzdOZwg@mail.gmail.com обсуждение исходный текст
Ответ на	PostgreSQL vs SQL Standard (Andrew Gierth <andrew@tao11.riddles.org.uk>)
Список	pgsql-hackers

On Sat, Jun 9, 2018 at 8:37 PM, Andrew Gierth <andrew@tao11.riddles.org.uk> wrote:

> I think I got all the issues I currently know of, but there may be

> more, and others may disagree with my classification of issues or the

> rationales for violating the spec. Any feedback?

Related to, but I think distinct from

"Trailing spaces in character(n)"

Trailing spaces in char(n) values are removed in contexts where the spec requires they be kept.

E021-03 Character literals subclause 5.3, "<literal>": <quote> [ <character representation>... ] <quote>

In subclause 5.3 (SQL standard 2011 part 2: foundation), <character string literal> is defined (ignoring

the character set specifier and the weird multi-line continuations) as

syntax rule 17 states

"The declared type of a <character string literal> is fixed-length character string."

In PostgreSQL, the same syntax (<quote> [ <character representation>... ] <quote>) is a string constant and in

the PostgreSQL documentation, section 4.1.2 constants, it says that string constants are one

of the three kinds of implicitly typed constants.

Where you see the difference is that trailing spaces in a string constant are retained when the type

is resolved to text, but if the constant was typed as bpchar and then cast to text, the trailing spaces

would be trimmed.

You also see that the type of a string constant is implicit in cases where PostgreSQL is

unable to determine the type of a string constant from its context.

I could be reading some of this incorrectly, but putting it all together, it looks to me like

PostgreSQL does not meet a strict interpretation of E021-03.

I'd put it in the WONTFIX section.

В списке pgsql-hackers по дате отправления:

От: Arseny Sher
Дата: 30 июня 2018 г., 21:00:21
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