I'm reading the vacuum code and I just noticed that the routines move_plain_tuple and move_chain_tuple expect the dest and source blocks to be locked, and unlock them at exit. The only caller of both is repair_frag, whose only caller in turn is full_vacuum_rel. Same thing for update_hint_bits.
So, the only callers of both has already acquired appropiate locks at the relation level -- nobody is going to be modifying the blocks while they proceed. So why bother locking the pages at all? Is there a reason or is this an historical accident?
-- Alvaro Herrera -- Valdivia, Chile Architect, www.EnterpriseDB.com "Puedes vivir solo una vez, pero si lo haces bien, una vez es suficiente"
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