"Simon Riggs" <[EMAIL PROTECTED]> wrote: > Read the heap blocks in sequence, but make a conditional lock for > cleanup on each block. If we don't get it, sleep, then try again when we > wake up. If we fail the second time, just skip the block completely.
When we allow some skips in removing dead tuples, can we guarantee pg_class.relfrozenxid? I think we might need additional "freezing-xmax" operations to avoid XID-wraparound in the first path of vacuum, though it hardly occurs. It might be a future topic ... if we are in the direciton of "optimistic sweeping", is it possible to remove the second path of vacuum completely? We just add XID of the vacuum to dead tuples we see in the first path. When backends find a dead tuple and see the transaction identified by XID in it has commited, they can freely reuse the area of the dead tuple because we can assume index entries pointing the tuple have been removed by the vacuum. We would use the infrastructure introduced by HOT for this purpose. Regards, --- ITAGAKI Takahiro NTT Open Source Software Center ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
