[CASSANDRA-15069] Tombstone/Partition not purged after gc_grace_seconds

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Not A Bug
• Fix Version/s: 3.11.5
• Component/s: Local/Compaction, Local/SSTable
• Severity: Normal
• Assignee: Unassigned
• Reporter: Pedro Gordo
• Created: 26/Mar/19 23:39
• Updated: 01/Aug/21 11:28
• Resolved: 08/Jul/19 16:32

Description

During a tombstone purge (reducing gc_grace_seconds to zero and running `nodetool garbagecollect`), I noticed that when doing a dump of the SSTable, sometimes, there are a few partitions that do not get completely purged, even with gc_grace_seconds set to zero. I was able to replicate this in a small test dataset, from which I have attached the SSTable files and the schema to this ticket so that you can verify this as well.
Doing a dump of the mc-51-big-Data.db file, you'll notice the following partition:

{
"partition" : {
"key" : [ "96" ],
"position" : 285,
"deletion_info" :

{ "marked_deleted" : "2019-03-14T21:31:55.244490Z", "local_delete_time" : "2019-03-14T21:31:55Z" }

},
"rows" : [ ]
},

As you can see, the rows were removed correctly by the garbagecollect, but the partition record, continues there, and never goes away.
From the client side, no data is returned, so it's good there. But regardless of that, this partition should not be present in the SSTable file.