>
> That would likely keep the extra storage requirements small, but still
> non-zero. Presumably the upgrade would be unnecessary if it could be done
> without rewriting files. Is there any rule of thumb for making sure one has
> enough space available for the upgrade? I suppose that would come down to
> what exactly needs to get rewritten, in what order, etc., but the pg_upgrade
> docs don't seem to have that detail. For example, since we've got an ~18TB
> table (including its indices), if that needs to be rewritten then we're still
> looking at requiring significant extra storage. Recent experience suggests
> postgres won't necessarily do things in the most storage-efficient way.. we
> just had a reindex on that database fail (in --single-user) because 17TB was
> insufficient free storage for the db to grow into.
>
Can you afford to drop and re-create those 6 indices?
