Re: [HACKERS] generated columns

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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