Ok, So then if you have a previous cell (c1) and you insert a new cell c2 that has a TTL of lets say 5 mins, then c1 should always exist? That is my understanding but from Cosmin’s post, he’s saying its different. And that’s why I don’t understand. You couldn’t lose the cell c1 at all. Compaction or no compaction.
That’s why I’m confused. Current behavior doesn’t match the expected contract. -Mike > On Apr 17, 2015, at 4:37 PM, Andrew Purtell <[email protected]> wrote: > > The way TTLs work today is they define the interval of time a cell > exists - exactly as that. There is no tombstone laid like a normal > delete. Once the TTL elapses the cell just ceases to exist to normal > scanners. The interaction of expired cells, multiple versions, minimum > versions, raw scanners, etc. can be confusing. We can absolutely > revisit this. > > A cell with an expired TTL could be treated as the combination of > tombstone and the most recent value it lays over. This is not how the > implementation works today, but could be changed for an upcoming major > version like 2.0 if there's consensus to do it. > > >> On Apr 10, 2015, at 7:26 AM, Cosmin Lehene <[email protected]> wrote: >> >> I've been initially puzzled by this, although I realize how it's likely as >> designed. >> >> >> The cell TTL expiration and compactions events can lead to either some (the >> older) data left or no data at all for a particular (row, family, >> qualifier, ts) coordinate. >> >> >> >> Write (r1, f1, q1, v1, 1) >> >> Write (r1, f1, q1, v1, 2) - TTL=1 minute >> >> >> Scenario 1: >> >> >> If a major compaction happens within a minute >> >> >> it will remove (r1, f1, q1, v1, 1) >> >> then after a minute (r1, f1, q1, v1, 2) will expire >> >> no data left >> >> >> Scenario 2: >> >> >> A minute passes >> >> (r1, f1, q1, v1, 2) expires >> >> Compaction runs.. >> >> (r1, f1, q1, v1, 1) remains >> >> >> >> This seems, by and large expected behavior, but it still seems >> "uncomfortable" that the (overall) outcome is not decided by me, but by a >> chance of event ordering. >> >> >> I wonder we'd want this to behave differently (perhaps it has been discussed >> already), but if not, it's worth a more detailed documentation in the book. >> >> >> What do you think? >> >> >> Cosmin >> >> >> >> > > -- > Best regards, > > - Andy > > Problems worthy of attack prove their worth by hitting back. - Piet > Hein (via Tom White) > The opinions expressed here are mine, while they may reflect a cognitive thought, that is purely accidental. Use at your own risk. Michael Segel michael_segel (AT) hotmail.com
