| From: | Nico Williams <nico(at)cryptonector(dot)com> |
|---|---|
| To: | Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> |
| Cc: | pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: generated columns |
| Date: | 2017-10-02 15:23:41 |
| Message-ID: | 20171002152338.GH1251@localhost |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
On Thu, Aug 31, 2017 at 12:16:43AM -0400, Peter Eisentraut wrote:
> In previous discussions, it has often been a source of confusion whether
> these generated columns are supposed to be computed on insert/update and
> stored, or computed when read. The SQL standard is not explicit, but
> appears to lean toward stored. DB2 stores. Oracle computes on read.
Question: How would one know the difference between storing computed
columns vs. computing them on read?
Answer?: Performance. If the computation is slow, then you'll really
notice on read.
Nico
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