[anarazel]

In the specific case of hashjoins, it does build them independently right now. There's a patch to rectify that though, by putting the hashtable also into shared memory. The coordination necessary to make multi phase batch joins and other such funny bits work, unfortunately made it infeasible to get into 10.

[halayli]

I stand corrected, it definitely reconstructs the hash table in each process.

[anarazel]

FWIW, here's the patchset to fix that: https://commitfest.postgresql.org/15/871/

[halayli]

Thanks! I remember reading this thread a while back and I thought it made it in.