This is managed via two new options, fetch_stats and remote_analyze, both are available at the server level and table level. If fetch_stats is true, then the ANALYZE command will first attempt to fetch statistics from the remote table and import those statistics locally.
If remote_analyze is true, and if the first attempt to fetch remote statistics found no attribute statistics, then an attempt will be made to ANALYZE the remote table before a second and final attempt to fetch remote statistics.
If no statistics are found, then ANALYZE will fall back to the normal behavior of sampling and local analysis.
I think the first step assumes that the remote stats are up-to-date; if they aren't, it would cause a regression. (If the remote relation is a plain table, they are likely to be up-to-date, but for example, if it is a foreign table, it's possible that they are stale.) So how about making it the user's responsibility to make them up-to-date? If doing so, we wouldn't need to do the second and third steps anymore, making the patch simple.
Obviously there is no way to know the quality/freshness of remote stats if they are found.
The analyze option was borne of feedback from other postgres hackers while brainstorming on what this option might look like. I don't think we *need* this extra option for the feature to be a success, but it's relative simplicity did make me want to put it out there to see who else liked it.
On the other hand:
This operation will only work on remote relations that can have stored statistics: tables, partitioned tables, and materialized views. If the remote relation is a view then remote fetching/analyzing is just wasted effort and the user is better of setting fetch_stats to false for that table.
I'm not sure the waste effort is acceptable; IMO, if the remote table is a view, I think that the system should detect that in some way, and then just do the normal ANALYZE processing.
The stats fetch query is pretty light, but I can see fetching the relkind along with the relstats, and making decisions on whether to continue from there, only applying the relstats after attrstats have been successfully applied.
