Literally just encountered this exact same thing. I couldn't find anything
in the official docs related to this but there is at least this blog that
explains it:
http://www.jsravn.com/2015/05/13/cassandra-tombstones-collections.html
and this entry in ScyllaDB's documentation:
http://www.scylladb.com/kb/sstable-interpretation/
Can confirm what Tyler mentioned, updating a single element does not cause
a tombstone.
On 25 May 2016 at 15:37, Tyler Hobbs <ty...@datastax.com> wrote:
> If you replace an entire collection, whether it's a map, set, or list, a
> range tombstone will be inserted followed by the new collection. If you
> only update a single element, no tombstones are generated.
>
> On Wed, May 25, 2016 at 9:48 AM, Matthias Niehoff <
> matthias.nieh...@codecentric.de> wrote:
>
>> Hi,
>>
>> we have a table with a Map Field. We do not delete anything in this
>> table, but to updates on the values including the Map Field (most of the
>> time a new value for an existing key, Rarely adding new keys). We now
>> encounter a huge amount of thumbstones for this Table.
>>
>> We used sstable2json to take a look into the sstables:
>>
>>
>> {"key": "Betty_StoreCatalogLines:7",
>>
>> "cells": [["276-1-6MPQ0RI-276110031802001001:","",1463820040628001],
>>
>> ["276-1-6MPQ0RI-276110031802001001:last_modified","2016-05-21
>> 08:40Z",1463820040628001],
>>
>>
>> ["276-1-6MPQ0RI-276110031802001001:last_modified_by_source:_","276-1-6MPQ0RI-276110031802001001:last_modified_by_source:!",1463040069753999,"t",1463040069],
>>
>>
>> ["276-1-6MPQ0RI-276110031802001001:last_modified_by_source:_","276-1-6MPQ0RI-276110031802001001:last_modified_by_source:!",1463120708590002,"t",1463120708],
>>
>>
>> ["276-1-6MPQ0RI-276110031802001001:last_modified_by_source:_","276-1-6MPQ0RI-276110031802001001:last_modified_by_source:!",1463145700735007,"t",1463145700],
>>
>>
>> ["276-1-6MPQ0RI-276110031802001001:last_modified_by_source:_","276-1-6MPQ0RI-276110031802001001:last_modified_by_source:!",1463157430862000,"t",1463157430],
>>
>>
>> [„276-1-6MPQ0RI-276110031802001001:last_modified_by_source:_“,“276-1-6MPQ0RI-276110031802001001:last_modified_by_source:!“,1463164595291002,"t",1463164595],
>>
>> . . .
>>
>>
>> ["276-1-6MPQ0RI-276110031802001001:last_modified_by_source:_","276-1-6MPQ0RI-276110031802001001:last_modified_by_source:!",1463820040628000,"t",1463820040],
>>
>>
>> ["276-1-6MPQ0RI-276110031802001001:last_modified_by_source:62657474795f73746f72655f636174616c6f675f6c696e6573","00000154d265c6b0",1463820040628001],
>>
>>
>> [„276-1-6MPQ0RI-276110031802001001:payload“,"{\"payload\":{\"Article
>> Id\":\"276110031802001001\",\"Row Id\":\"1-6MPQ0RI\",\"Article
>> #\":\"31802001001\",\"Quote Item Id\":\"1-6MPWPVC\",\"Country
>> Code\":\"276\"}}",1463820040628001]
>>
>>
>>
>> Looking at the SStables it seem like every update of a value in a Map
>> breaks down to a delete and insert in the corresponding SSTable (see all
>> the thumbstone flags „t“ in the extract of sstable2json above).
>>
>> We are using Cassandra 2.2.5.
>>
>> Can you confirm this behavior?
>>
>> Thanks!
>> --
>> Matthias Niehoff | IT-Consultant | Agile Software Factory | Consulting
>> codecentric AG | Zeppelinstr 2 | 76185 Karlsruhe | Deutschland
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>
>
>
> --
> Tyler Hobbs
> DataStax <http://datastax.com/>
>
--
Kurt Greaves
k...@instaclustr.com
www.instaclustr.com
