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Update type-conversion documentation for long-ago changes.

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This example wasn't updated when we changed the behavior of bpcharlen()
in 8.0, nor when we changed the number of parameters taken by the bpchar()
cast function in 7.3.  Per report from lsliang.
This commit is contained in:
Tom Lane 2011-09-06 12:14:51 -04:00
parent d764835bbc
commit b7f83e70d9
1 changed files with 12 additions and 10 deletions
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22
doc/src/sgml/typeconv.sgml
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@ -758,9 +758,11 @@ cast is a cast from that type to itself. If one is found in the
<structname>pg_cast</> catalog, apply it to the expression before storing
into the destination column. The implementation function for such a cast
always takes an extra parameter of type <type>integer</type>, which receives
the destination column's declared length (actually, its
<structfield>atttypmod</> value; the interpretation of
<structfield>atttypmod</> varies for different data types). The cast function
the destination column's <structfield>atttypmod</> value (typically its
declared length, although the interpretation of <structfield>atttypmod</>
varies for different data types), and it may take a third <type>boolean</>
parameter that says whether the cast is explicit or implicit. The cast
function
is responsible for applying any length-dependent semantics such as size
checking or truncation.
</para>
@ -772,17 +774,17 @@ checking or truncation.
<title><type>character</type> Storage Type Conversion</title>
<para>
For a target column declared as <type>character(20)</type> the following statement
ensures that the stored value is sized correctly:
For a target column declared as <type>character(20)</type> the following
statement shows that the stored value is sized correctly:
<screen>
CREATE TABLE vv (v character(20));
INSERT INTO vv SELECT 'abc' || 'def';
SELECT v, length(v) FROM vv;
SELECT v, octet_length(v) FROM vv;
v | length
----------------------+--------
abcdef | 20
v | octet_length
----------------------+--------------
abcdef | 20
(1 row)
</screen>
</para>
@ -796,7 +798,7 @@ char</>, the internal name of the <type>character</type> data type) to match the
column type. (Since the conversion from <type>text</type> to
<type>bpchar</type> is binary-coercible, this conversion does
not insert any real function call.) Finally, the sizing function
<literal>bpchar(bpchar, integer)</literal> is found in the system catalog
<literal>bpchar(bpchar, integer, boolean)</> is found in the system catalog
and applied to the operator's result and the stored column length. This
type-specific function performs the required length check and addition of
padding spaces.