database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-06-11 20:28:21 +03:00
Code Activity

Fix things so that array_agg_finalfn does not modify or free its input

Browse Source 
ArrayBuildState, per trouble report from Merlin Moncure.  By adopting
this fix, we are essentially deciding that aggregate final-functions
should not modify their inputs ever.  Adjust documentation and comments
to match that conclusion.
This commit is contained in:
Tom Lane
2009-06-20 18:45:28 +00:00
parent 87698ffa8e
commit 82480e28f5
4 changed files with 31 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
doc/src/sgml/xaggr.sgml
View File

@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/xaggr.sgml,v 1.37 2008/12/28 18:53:54 tgl Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/xaggr.sgml,v 1.38 2009/06/20 18:45:28 tgl Exp $ -->
<sect1 id="xaggr">
<title>User-Defined Aggregates</title>
@ -175,10 +175,14 @@ SELECT attrelid::regclass, array_accum(atttypid::regtype)
(IsA(fcinfo-&gt;context, AggState) ||
IsA(fcinfo-&gt;context, WindowAggState)))
</programlisting>
One reason for checking this is that when it is true, the first input
One reason for checking this is that when it is true for a transition
function, the first input
must be a temporary transition value and can therefore safely be modified
in-place rather than allocating a new copy. (This is the <emphasis>only</>
case where it is safe for a function to modify a pass-by-reference input.)
case where it is safe for a function to modify a pass-by-reference input.
In particular, aggregate final functions should not modify their inputs in
any case, because in some cases they will be re-executed on the same
final transition value.)
See <literal>int8inc()</> for an example.
</para>