Tom Lane <[EMAIL PROTECTED]>: > Atsushi Ogawa <[EMAIL PROTECTED]> writes: > > When _bt_check_unique finds a dead item that has same data as new > > item, LP_DEAD is set to the item. Can we reuse this dead item instead > > of inserting new item? > > This strikes me as a pretty bad idea for the same reason pointed out > recently in other threads: the notion of equality embodied in a btree > opclass' equals function may have little or nothing to do with true > identity. So your assumption that it's the "same" data is faulty.
Thanks, I understand the problem. When the size of new item and dead item is the equal, the new item can be overwrited at the position of the dead item. > Also, I'm dubious about the assumption that "can be marked LP_DELETED" > is the same as "can be physically removed right now". The side-effects > on indexscans happening concurrently with yours could be bad. At the > very least you'd need to obtain super-exclusive lock (cf btbulkdelete) > before doing the replacement. I agree. I will add code that checks the refcount of buffer. If refcount is 1, current process has super-exclusive lock, and we can overwrite the dead item. If refcount > 1, I use _bt_insertonpg. regards, --- Atsushi Ogawa ---------------------------(end of broadcast)--------------------------- TIP 2: Don't 'kill -9' the postmaster
