Re: generated columns

From: Serge Rielau <serge(at)rielau(dot)com>
To: Jaime Casanova <jaime(dot)casanova(at)2ndquadrant(dot)com>
Cc: Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: generated columns
Date: 2017-09-12 21:26:40
Message-ID: BFDFB10B-27E1-4427-B304-EEDC47578327@rielau.com
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> On Sep 12, 2017, at 12:35 PM, Jaime Casanova <jaime(dot)casanova(at)2ndquadrant(dot)com> wrote:
>
> also is interesting that in triggers, both before and after, the
> column has a null. that seems reasonable in a before trigger but not
> in an after trigger
Why is a NULL reasonable for before triggers?
If I create a table with a column with default and I omit that column on INSERT
Is the column value also NULL in the before trigger? (I hope not)

BTW, the original idea behind generated columns was to materialize them.
Reason being to avoid expensive computations of frequently used expressions
(and to support indexing in the absence of indexes with expressions)

You may find the following amusing:
https://www.ibm.com/developerworks/community/blogs/SQLTips4DB2LUW/entry/expression_generated_columns?lang=en <https://www.ibm.com/developerworks/community/blogs/SQLTips4DB2LUW/entry/expression_generated_columns?lang=en>

Cheers
Serge Rielau
salesforce.com

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