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Allow casting between bytea and integer types.

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This allows smallint, integer, and bigint values to be cast to and
from bytea. The bytea value is the two's complement representation of
the integer, with the most significant byte first. For example:

  1234::bytea -> \x000004d2
  (-1234)::bytea -> \xfffffb2e

Author: Aleksander Alekseev <aleksander@timescale.com>
Reviewed-by: Joel Jacobson <joel@compiler.org>
Reviewed-by: Yugo Nagata <nagata@sraoss.co.jp>
Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Dean Rasheed <dean.a.rasheed@gmail.com>
Discussion: https://postgr.es/m/CAJ7c6TPtOp6%2BkFX5QX3fH1SVr7v65uHr-7yEJ%3DGMGQi5uhGtcA%40mail.gmail.com
This commit is contained in:
Dean Rasheed
2025-03-07 09:31:18 +00:00
parent d611f8b158
commit 6da469bada
8 changed files with 281 additions and 1 deletions
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17
doc/src/sgml/func.sgml
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@@ -5035,6 +5035,23 @@ SELECT format('Testing %3$s, %2$s, %s', 'one', 'two', 'three');
</variablelist>
</para>
<para>
In addition, it is possible to cast integral values to and from type
<type>bytea</type>. Casting an integer to <type>bytea</type> produces
2, 4, or 8 bytes, depending on the width of the integer type. The result
is the two's complement representation of the integer, with the most
significant byte first. Some examples:
<programlisting>
1234::smallint::bytea <lineannotation>\x04d2</lineannotation>
cast(1234 as bytea) <lineannotation>\x000004d2</lineannotation>
cast(-1234 as bytea) <lineannotation>\xfffffb2e</lineannotation>
'\x8000'::bytea::smallint <lineannotation>-32768</lineannotation>
'\x8000'::bytea::integer <lineannotation>32768</lineannotation>
</programlisting>
Casting a <type>bytea</type> to an integer will raise an error if the
length of the <type>bytea</type> exceeds the width of the integer type.
</para>
<para>
See also the aggregate function <function>string_agg</function> in
<xref linkend="functions-aggregate"/> and the large object functions