Btw, if you seen the number of tombstones that is a multiply of number of scanned rows, like in your case - that’s a explicit signal of either null inserts, or non frozen collections...
On Fri 21. Aug 2020 at 20:21, Attila Wind <attilaw@swf.technology> wrote: > > > > > > > > > > > right! silly me (regarding "can't have null for clustering > > column") :-) > > > OK code is modified, we stopped using NULL on that column. In a > > few days we will see if this was the cause. > > > Thanks for the useful info eveyrone! Helped a lot! > > > > > Attila Wind > > > > > > > > http://www.linkedin.com/in/attilaw > > > Mobile: +49 176 43556932 > > > > > > > > > > > > > 21.08.2020 11:04 keltezéssel, Alex Ott > > írta: > > > > > > > > > > > inserting null for any column will generate the tombstone > > (and you can't have null for clustering column, except case > > when it's an empty partition with static column). > > > if you're really inserting the new data, not overwriting > > existing one - use UNSET instead of null > > > > > > > > > > > > On Fri, Aug 21, 2020 at 10:45 > > AM Attila Wind <attilaw@swf.technology> <attilaw@swf.technology> wrote: > > > > > >> >> >> >> Thanks a lot! I will process every pointers you gave - >> >> appreciated! >> >> >> >> >> 1. we do have collection column in that table but that is >> >> (we have only 1 column) a frozen Map - so I guess >> >> "Tombstones are also implicitly created any time you >> >> insert or update a row which has an (unfrozen) collection >> >> column: list<>, map<> or set<>. This >> >> has to be done in order to ensure the new write replaces >> >> any existing collection entries." does not really apply >> >> here >> >> >> 2. "Isn’t it so that explicitly >> >> setting a column to NULL also result in a tombstone" >> >> >> Is this true for all columns? or just clustering key cols? >> >> >> Because if for all cols (which would make sense maybe to >> >> me more) then we found the possible reason.. :-) >> >> >> As we do have an Integer coulmn there which is actually >> >> NULL often (and so far in all cases) >> >> >> >> >> >> >> >> >> >> Attila >> >> Wind >> >> >> >> >> >> >> >> http://www.linkedin.com/in/attilaw >> >> >> Mobile: +49 176 43556932 >> >> >> >> >> >> >> >> >> >> >> 21.08.2020 09:49 keltezéssel, Oleksandr Shulgin írta: >> >> >> >> >> >> >> >> >> On Fri, Aug 21, 2020 at 9:43 AM Tobias >> >> Eriksson <tobias.eriks...@qvantel.com> >> >> wrote: >> >> >> >> >> >> >> >>> >>> >>> >>> >>> >>> Isn’t it >>> >>> so that explicitly setting a column to NULL >>> >>> also result in a tombstone >>> >>> >>> >>> >>> >>> >>> >> >> >> >> >> >> >> True, thanks for pointing that out! >> >> >> >> >> >> >> >> >>> >>> >>> >>> >>> >>> >>> >>> Then as >>> >>> mentioned the use of list,set,map can also >>> >>> result in tombstones >>> >>> >>> See >>> >>> >>> https://www.instaclustr.com/cassandra-collections-hidden-tombstones-and-how-to-avoid-them/ >>> >>> >>> >>> >>> >>> >>> >> >> >> >> >> >> >> And A. Ott has already mentioned both these >> >> possible reasons :-) >> >> >> >> >> >> >> >> -- >> >> >> Alex >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> > > > > > > > > > > -- > > > > > > > With best wishes, Alex Ott > > > http://alexott.net/ > > > Twitter: alexott_en (English), alexott (Russian) > > > > > > > > > > > > > > > -- With best wishes, Alex Ott http://alexott.net/ Twitter: alexott_en (English), alexott (Russian)
