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Make length() disregard trailing spaces in char(n) values, per discussion

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some time ago and recent patch from Gavin Sherry.  Update documentation
to point out that trailing spaces are insignificant in char(n).
This commit is contained in:
Tom Lane 2004-02-01 06:27:48 +00:00
parent 08b0e60563
commit f27976c85b
2 changed files with 27 additions and 9 deletions
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20
doc/src/sgml/datatype.sgml
View File

@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/datatype.sgml,v 1.140 2004/01/20 22:46:06 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/datatype.sgml,v 1.141 2004/02/01 06:27:48 tgl Exp $
-->
<chapter id="datatype">
@ -901,6 +901,18 @@ CREATE TABLE <replaceable class="parameter">tablename</replaceable> (
management systems have it as well.
</para>
<para>
Values of type <type>character</type> are physically padded
with spaces to the specified width <replaceable>n</>, and are
stored and displayed that way. However, the padding spaces are
treated as semantically insignificant. Trailing spaces are
disregarded when comparing two values of type <type>character</type>,
and they will be removed when converting a <type>character</type> value
to one of the other string types. Note that trailing spaces
<emphasis>are</> semantically significant in
<type>character varying</type> and <type>text</type> values.
</para>
<para>
The storage requirement for data of these types is 4 bytes plus the
actual string, and in case of <type>character</type> plus the
@ -922,7 +934,11 @@ CREATE TABLE <replaceable class="parameter">tablename</replaceable> (
<para>
There are no performance differences between these three types,
apart from the increased storage size when using the blank-padded
type.
type. While <type>character(<replaceable>n</>)</type> has performance
advantages in some other database systems, it has no such advantages in
<productname>PostgreSQL</productname>. In most situations
<type>text</type> or <type>character varying</type> should be used
instead.
</para>
</tip>

16
src/backend/utils/adt/varchar.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/adt/varchar.c,v 1.103 2003/11/29 19:51:59 pgsql Exp $
* $PostgreSQL: pgsql/src/backend/utils/adt/varchar.c,v 1.104 2004/02/01 06:27:48 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -510,14 +510,16 @@ Datum
bpcharlen(PG_FUNCTION_ARGS)
{
BpChar *arg = PG_GETARG_BPCHAR_P(0);
int len;
/* optimization for single byte encoding */
if (pg_database_encoding_max_length() <= 1)
PG_RETURN_INT32(VARSIZE(arg) - VARHDRSZ);
/* get number of bytes, ignoring trailing spaces */
len = bcTruelen(arg);
/* in multibyte encoding, convert to number of characters */
if (pg_database_encoding_max_length() != 1)
len = pg_mbstrlen_with_len(VARDATA(arg), len);
PG_RETURN_INT32(
pg_mbstrlen_with_len(VARDATA(arg), VARSIZE(arg) - VARHDRSZ)
);
PG_RETURN_INT32(len);
}
Datum