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From: Sergei Katkovsky <[email protected]>
To: Laurenz Albe <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: Jeff Davis <[email protected]>
Cc: [email protected]
Subject: Re: BPCHAR description in 8.3. Character Types is misleading and incomplete
Date: Fri, 17 Oct 2025 18:18:08 +0400
Message-ID: <CAAf8JyLJDtbBnx7zc_oPb=16YAHH0PyAh5H_GtZ7R0QJPqthNQ@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>

On Fri, Oct 17, 2025 at 4:49 PM Laurenz Albe <[email protected]> wrote:

> "bpchar" and "varchar", when used without type modifier, are actually
> identical:
>
> SELECT octet_length(BPCHAR 'x   '),
>        octet_length(VARCHAR 'x   '),
>        octet_length(TEXT 'x   ');
>
>  octet_length │ octet_length │ octet_length
> ══════════════╪══════════════╪══════════════
>             4 │            4 │            4
>
> The blank-trimming only occurs when a "bpchar" is converted to "text",
> for example when used with the concatenation operator.

Unfortunately, BPCHAR and VARCHAR are not identical in other contexts.
The situation is not the same as with BCHAR(n), which is just an alias
for CHAR(n).
SELECT BPCHAR 'x' = VARCHAR 'x   ', VARCHAR 'x' = BPCHAR 'x   ',
VARCHAR 'x' = VARCHAR 'x   ';
true true false
For comparison with BPCHAR trailing blanks are insignificant, but when
we have VARCHAR on both sides, they matter.

With best regards,
Sergei Katkovskii

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