mirror of
https://git.postgresql.org/git/postgresql.git
synced 2024-09-01 11:57:22 +02:00
Doc: remove ancient comment.
There's a very old comment in rules.sgml added back to 2003. It expected to a feature coming back but it never happened. So now we can safely remove the comment. Back-patched to all supported branches. Discussion: https://postgr.es/m/20190211.191004.219630835457494660.t-ishii%40sraoss.co.jp
This commit is contained in:
parent
3cbbd3515a
commit
d43a1ff8f2
@ -2434,30 +2434,6 @@ Nestloop
|
|||||||
in a command.
|
in a command.
|
||||||
</para>
|
</para>
|
||||||
|
|
||||||
<!-- What's happening with this? If it doesn't come back, remove this section. -->
|
|
||||||
<!--
|
|
||||||
<para>
|
|
||||||
Another situation is cases on <command>UPDATE</command> where it depends on the
|
|
||||||
change of an attribute if an action should be performed or
|
|
||||||
not. The only way to
|
|
||||||
create a rule as in the shoelace_log example is to do it with
|
|
||||||
a rule qualification. That results in an extra query that is
|
|
||||||
performed always, even if the attribute of interest cannot
|
|
||||||
change at all because it does not appear in the target list
|
|
||||||
of the initial query. When this is enabled again, it will be
|
|
||||||
one more advantage of rules over triggers. Optimization of
|
|
||||||
a trigger must fail by definition in this case, because the
|
|
||||||
fact that its actions will only be done when a specific attribute
|
|
||||||
is updated is hidden in its functionality. The definition of
|
|
||||||
a trigger only allows to specify it on row level, so whenever a
|
|
||||||
row is touched, the trigger must be called to make its
|
|
||||||
decision. The rule system will know it by looking up the
|
|
||||||
target list and will suppress the additional query completely
|
|
||||||
if the attribute isn't touched. So the rule, qualified or not,
|
|
||||||
will only do its scans if there ever could be something to do.
|
|
||||||
</para>
|
|
||||||
-->
|
|
||||||
|
|
||||||
<para>
|
<para>
|
||||||
The summary is, rules will only be significantly slower than
|
The summary is, rules will only be significantly slower than
|
||||||
triggers if their actions result in large and badly qualified
|
triggers if their actions result in large and badly qualified
|
||||||
|
Loading…
Reference in New Issue
Block a user