database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-12-18 05:01:01 +03:00
Code Activity

Add range_minus_multi and multirange_minus_multi functions

Browse Source 
The existing range_minus function raises an exception when the range is
"split", because then the result can't be represented by a single range.
For example '[0,10)'::int4range - '[4,5)' would be '[0,4)' and '[5,10)'.

This commit adds new set-returning functions so that callers can get
results even in the case of splits. There is no risk of an exception for
multiranges, but a set-returning function lets us handle them the same
way we handle ranges.

Both functions return zero results if the subtraction would give an
empty range/multirange.

The main use-case for these functions is to implement UPDATE/DELETE FOR
PORTION OF, which must compute the application-time of "temporal
leftovers": the part of history in an updated/deleted row that was not
changed. To preserve the untouched history, we will implicitly insert
one record for each result returned by range/multirange_minus_multi.
Using a set-returning function will also let us support user-defined
types for application-time update/delete in the future.

Author: Paul A. Jungwirth <pj@illuminatedcomputing.com>
Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/ec498c3d-5f2b-48ec-b989-5561c8aa2024%40illuminatedcomputing.com
This commit is contained in:
Peter Eisentraut
2025-11-22 09:40:00 +01:00
parent 0dceba21d7
commit 5eed8ce50c
10 changed files with 493 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

42
doc/src/sgml/func/func-range.sgml
View File

@@ -842,6 +842,29 @@
<returnvalue>[1,4)</returnvalue>
</para></entry>
</row>
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
<primary>range_minus_multi</primary>
</indexterm>
<function>range_minus_multi</function> ( <type>anyrange</type>, <type>anyrange</type> )
<returnvalue>setof anyrange</returnvalue>
</para>
<para>
Returns the non-empty range(s) remaining after subtracting the second range from the first.
One row is returned for each range, so if the second range splits the first into two parts,
there will be two results. If the subtraction yields an empty range, no rows are returned.
</para>
<para>
<literal>range_minus_multi('[0,10)'::int4range, '[3,4)'::int4range)</literal>
<returnvalue></returnvalue>
<programlisting>
[0,3)
[4,10)
</programlisting>
</para></entry>
</row>
</tbody>
</tgroup>
</table>
@@ -1041,6 +1064,25 @@
</programlisting>
</para></entry>
</row>
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
<primary>multirange_minus_multi</primary>
</indexterm>
<function>multirange_minus_multi</function> ( <type>anymultirange</type>, <type>anymultirange</type> )
<returnvalue>setof anymultirange</returnvalue>
</para>
<para>
Returns the non-empty multirange(s) remaining after subtracting the second multirange from the first.
If the subtraction yields an empty multirange, no rows are returned.
Two rows are never returned, because a single multirange can always accommodate any result.
</para>
<para>
<literal>multirange_minus_multi('{[0,10)}'::int4multirange, '{[3,4)}'::int4multirange)</literal>
<returnvalue>{[0,3), [4,10)}</returnvalue>
</para></entry>
</row>
</tbody>
</tgroup>
</table>