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

This patch seems to be missing a call to RelationAssumeNewRelfilenode() in
reindex_index().

That's maybe the related to the cause of the crashes I pointed out earlier this
year.

Alexey's v4 patch changed RelationSetNewRelfilenode() to accept a tablespace
parameter, but Michael seemed to object to that. However that seems cleaner
and ~30 line shorter.

Michael, would you comment on that ? The v4 patch and your comments are here.
https://www.postgresql.org/message-id/attachment/105574/v4-0001-Allow-REINDEX-and-REINDEX-CONCURRENTLY-to-change-tablespace.patch
https://www.postgresql.org/message-id/20191127035416.GG5435%40paquier.xyz

> --- a/src/backend/catalog/index.c
> +++ b/src/backend/catalog/index.c
> @@ -3480,6 +3518,47 @@ reindex_index(Oid indexId, bool skip_constraint_checks, char persistence,
> */
> CheckTableNotInUse(iRel, "REINDEX INDEX");
>
> + if (tablespaceOid == MyDatabaseTableSpace)
> + tablespaceOid = InvalidOid;
> +
> + /*
> + * Set the new tablespace for the relation. Do that only in the
> + * case where the reindex caller wishes to enforce a new tablespace.
> + */
> + if (set_tablespace &&
> + tablespaceOid != iRel->rd_rel->reltablespace)
> + {
> + Relation pg_class;
> + Form_pg_class rd_rel;
> + HeapTuple tuple;
> +
> + /* First get a modifiable copy of the relation's pg_class row */
> + pg_class = table_open(RelationRelationId, RowExclusiveLock);
> +
> + tuple = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(indexId));
> + if (!HeapTupleIsValid(tuple))
> + elog(ERROR, "cache lookup failed for relation %u", indexId);
> + rd_rel = (Form_pg_class) GETSTRUCT(tuple);
> +
> + /*
> + * Mark the relation as ready to be dropped at transaction commit,
> + * before making visible the new tablespace change so as this won't
> + * miss things.
> + */
> + RelationDropStorage(iRel);
> +
> + /* Update the pg_class row */
> + rd_rel->reltablespace = tablespaceOid;
> + CatalogTupleUpdate(pg_class, &tuple->t_self, tuple);
> +
> + heap_freetuple(tuple);
> +
> + table_close(pg_class, RowExclusiveLock);
> +
> + /* Make sure the reltablespace change is visible */
> + CommandCounterIncrement();