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
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