Hi, I apologise for a late response I wanted to run some further tests so I can provide more information to you.
@Jeff, no I don't set the "only_purge_repaired_tombstone" option. It should be default: False. But no I don't run repairs during the tests. @Eric, I understand that rapid deletes/inserts are some kind of antipattern, nevertheless I'm not experiencing any problems with that (except for the 2nd indices). Update: I run a new test where I delete the indexed columns extra, plus delete the whole row at the end. And surprisingly this test scenario works fine. Using nodetool flush + compact (in order to expedite the test) seems to always purge the index table. So that's great because I seem to have found a workaround, on the other hand, could there be a bug in Cassandra - leaking index table? Test details: Create table with LeveledCompactionStrategy; 'tombstone_compaction_interval': 60; gc_grace_seconds=60 There are two indexed columns for comparison: column1, column2 Insert keys {1..x} with random values in column1 & column2 Delete {key:column2} (but not column1) Delete {key} Repeat n-times from the inserts Wait 1 minute nodetool flush nodetool compact (sometimes compact <keyspace> <table.index> nodetool cfstats What I observe is, that the data table is empty, column2 index table is also empty and column1 index table has non-zero (leaked) "space used" and "estimated rows". Roman On 18 May 2018 at 16:13, Jeff Jirsa <jji...@gmail.com> wrote: > This would matter for the base table, but would be less likely for the > secondary index, where the partition key is the value of the base row > > Roman: there’s a config option related to only purging repaired tombstones > - do you have that enabled ? If so, are you running repairs? > > -- > Jeff Jirsa > > > > On May 18, 2018, at 6:41 AM, Eric Stevens <migh...@gmail.com> wrote: > > > > The answer to Question 3 is "yes." One of the more subtle points about > > tombstones is that Cassandra won't remove them during compaction if there > > is a bloom filter on any SSTable on that replica indicating that it > > contains the same partition (not primary) key. Even if it is older than > > gc_grace, and would otherwise be a candidate for cleanup. > > > > If you're recycling partition keys, your tombstones may never be able to > be > > cleaned up, because in this scenario there is a high probability that an > > SSTable not involved in that compaction also contains the same partition > > key, and so compaction cannot have confidence that it's safe to remove > the > > tombstone (it would have to fully materialize every record in the > > compaction, which is too expensive). > > > > In general it is an antipattern in Cassandra to write to a given > partition > > indefinitely for this and other reasons. > > > > On Fri, May 18, 2018 at 2:37 AM Roman Bielik < > > roman.bie...@openmindnetworks.com> wrote: > > > >> Hi, > >> > >> I have a Cassandra 3.11 table (with compact storage) and using secondary > >> indices with rather unique data stored in the indexed columns. There are > >> many inserts and deletes, so in order to avoid tombstones piling up I'm > >> re-using primary keys from a pool (which works fine). > >> I'm aware that this design pattern is not ideal, but for now I can not > >> change it easily. > >> > >> The problem is, the size of 2nd index tables keeps growing (filled with > >> tombstones) no matter what. > >> > >> I tried some aggressive configuration (just for testing) in order to > >> expedite the tombstone removal but with little-to-zero effect: > >> COMPACTION = { 'class': > >> 'LeveledCompactionStrategy', 'unchecked_tombstone_compaction': 'true', > >> 'tombstone_compaction_interval': 600 } > >> gc_grace_seconds = 600 > >> > >> I'm aware that perhaps Materialized views could provide a solution to > this, > >> but I'm bind to the Thrift interface, so can not use them. > >> > >> Questions: > >> 1. Is there something I'm missing? How come compaction does not remove > the > >> obsolete indices/tombstones from 2nd index tables? Can I trigger the > >> cleanup manually somehow? > >> I have tried nodetool flush, compact, rebuild_index on both data table > and > >> internal Index table, but with no result. > >> > >> 2. When deleting a record I'm deleting the whole row at once - which > would > >> create one tombstone for the whole record if I'm correct. Would it help > to > >> delete the indexed columns separately creating extra tombstone for each > >> cell? > >> As I understand the underlying mechanism, the indexed column value must > be > >> read in order a proper tombstone for the index is created for it. > >> > >> 3. Could the fact that I'm reusing the primary key of a deleted record > >> shortly for a new insert interact with the secondary index tombstone > >> removal? > >> > >> Will be grateful for any advice. > >> > >> Regards, > >> Roman > >> > >> -- > >> <http://www.openmindnetworks.com> > >> <http://www.openmindnetworks.com/> > >> <https://www.linkedin.com/company/openmind-networks> > >> <https://twitter.com/Openmind_Ntwks> <http://www.openmindnetworks.com/ > > > >> > > --------------------------------------------------------------------- > To unsubscribe, e-mail: dev-unsubscr...@cassandra.apache.org > For additional commands, e-mail: dev-h...@cassandra.apache.org > > -- <http://www.openmindnetworks.com> <http://www.openmindnetworks.com/> <https://www.linkedin.com/company/openmind-networks> <https://twitter.com/Openmind_Ntwks> <http://www.openmindnetworks.com/>