Re: Allow CLUSTER, VACUUM FULL and REINDEX to change tablespace on the fly

On Wed, Jan 20, 2021 at 03:34:39PM -0300, Alvaro Herrera wrote:
> On 2021-Jan-20, Alexey Kondratov wrote:
>> Ugh, forgot to attach the patches. Here they are.
>
> Yeah, looks reasonable.

Patch 0002 still has a whole set of issues as I pointed out a couple
of hours ago, but if we agree on 0001 as being useful if done
independently, I'd rather get that done first. This way or just
merging both things in a single commit is not a big deal seeing the
amount of code, so I am fine with any approach. It may be possible
that 0001 requires more changes depending on the work to-be-done for
0002 though?

>> + /* No work if no change in tablespace. */
>> + oldTablespaceOid = rd_rel->reltablespace;
>> + if (tablespaceOid != oldTablespaceOid ||
>> + (tablespaceOid == MyDatabaseTableSpace && OidIsValid(oldTablespaceOid)))
>> + {
>> + /* Update the pg_class row. */
>> + rd_rel->reltablespace = (tablespaceOid == MyDatabaseTableSpace) ?
>> + InvalidOid : tablespaceOid;
>> + CatalogTupleUpdate(pg_class, &tuple->t_self, tuple);
>> +
>> + changed = true;
>> + }
>> +
>> + if (changed)
>> + /* Record dependency on tablespace */
>> + changeDependencyOnTablespace(RelationRelationId,
>> + reloid, rd_rel->reltablespace);
>
> Why have a separate "if (changed)" block here instead of merging with
> the above?

Yep.

+ if (SetRelTablespace(reloid, newTableSpace))
+ /* Make sure the reltablespace change is visible */
+ CommandCounterIncrement();
At quick glance, I am wondering why you just don't do a CCI within
SetRelTablespace().
--
Michael