Horton

Re: generated columns

Nico Williams <nico@cryptonector.com>

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From: Nico Williams <nico@cryptonector.com>
To: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2017-10-02T15:23:41Z
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
--

Commits

  1. Generated columns

  2. Add walreceiver API to get remote server version

  3. Add pg_partition_tree to display information about partitions

  4. pg_restore: Augment documentation for -N option

  5. Change delimiter used for display of NextXID