Re: [HACKERS] generated columns

On 19/11/2018 19:54, Alvaro Herrera wrote:
> It's unclear why you made generated columns on partitions unsupported.
> I'd fix the limitation if possible, but if not, at least document it.

This is explained here:

+ /*
+ * Generated columns in partition key expressions:
+ *
+ * - Stored generated columns cannot work: They are computed
+ * after BEFORE triggers, but partition routing is done
+ * before all triggers.
+ *
+ * - Virtual generated columns could work. But there is a
+ * problem when dropping such a table: Dropping a table
+ * calls relation_open(), which causes partition keys to be
+ * constructed for the partcache, but at that point the
+ * generation expression is already deleted (through
+ * dependencies), so this will fail. So if you remove the
+ * restriction below, things will appear to work, but you
+ * can't drop the table. :-(
+ */

> (I particularly notice that partition key is marked as unsupported in
> the regression test. Consider partitioning on a SERIAL column, this is
> clearly something that users will expect to work.)

A serial column is not a generated column.

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Peter Eisentraut http://www.2ndQuadrant.com/
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