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https://issues.apache.org/jira/browse/CASSANDRA-21000?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18038898#comment-18038898
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Branimir Lambov commented on CASSANDRA-21000:
---------------------------------------------
Do I understand correctly that the problem is that sstable files remember
dropped columns for which they contain no data?
I don't see a reason why this should be the case; the purpose of the columns
definition in the sstable header is to be able to read the data correctly. If
data for a column is not present, its definition should not be needed.
The database state itself, however, should not forget dropped column
definitions, because this may cause problems when the column is recreated with
a different type.
> Deleted columns are forever part of SerializationHeader
> -------------------------------------------------------
>
> Key: CASSANDRA-21000
> URL: https://issues.apache.org/jira/browse/CASSANDRA-21000
> Project: Apache Cassandra
> Issue Type: Improvement
> Reporter: Cameron Zemek
> Assignee: Stefan Miklosovic
> Priority: Normal
> Time Spent: 20m
> Remaining Estimate: 0h
>
> If you delete a column and rewrite the SSTable the column is removed from the
> data, but the serialization header refers to the deleted column still. This
> means if you drop a column and rewrite sstables (eg. nodetool upgradesstables
> -a) and that column is not in use, you still can not import or load those
> SSTables into another cluster without also having to add/drop columns.
>
> {noformat}
> ~/.ccm/test/node1/data0/test $ ~/bin/cqlsh
> Connected to repairtest at 127.0.0.1:9042
> [cqlsh 6.2.0 | Cassandra 5.0.5-SNAPSHOT | CQL spec 3.4.7 | Native protocol v5]
> Use HELP for help.
> cqlsh> CREATE TABLE test.drop_test(id int primary key, message text,
> col_to_delete text);
> cqlsh> INSERT INTO test.drop_test(id, message, col_to_delete) VALUES (1,
> 'test', 'delete me');
> cqlsh> SELECT * FROM test.drop_test;
> id | col_to_delete | message
> ----+---------------+---------
> 1 | delete me | test
> (1 rows)
> ~/.ccm/test/node1/data0/test $ ccm flush
> ~/.ccm/test/node1/data0/test $ cd drop_test-7a20f690ba8611f09c6c3125f1cbdf37
> ~/.ccm/test/node1/data0/test $ ls
> nb-1-big-CompressionInfo.db nb-1-big-Digest.crc32 nb-1-big-Index.db
> nb-1-big-Summary.db
> nb-1-big-Data.db nb-1-big-Filter.db nb-1-big-Statistics.db
> nb-1-big-TOC.txt
> ~/.ccm/test/node1/data0/test $ /.ccm/repository/5.0.3/tools/bin/sstabledump
> nb-1-big-Data.db
> [
> {
> "table kind" : "REGULAR",
> "partition" : {
> "key" : [ "1" ],
> "position" : 0
> },
> "rows" : [
> {
> "type" : "row",
> "position" : 18,
> "liveness_info" : { "tstamp" : "2025-11-05T20:32:17.946616Z" },
> "cells" : [
> { "name" : "col_to_delete", "value" : "delete me" },
> { "name" : "message", "value" : "test" }
> ]
> }
> ]
> }
> ]%
> ~/.ccm/test/node1/data0/test $ ~/bin/cqlsh
> Connected to repairtest at 127.0.0.1:9042
> [cqlsh 6.2.0 | Cassandra 5.0.5-SNAPSHOT | CQL spec 3.4.7 | Native protocol v5]
> Use HELP for help.
> cqlsh> ALTER TABLE test.drop_test DROP col_to_delete;
> cqlsh> SELECT * FROM test.drop_test;
> id | message
> ----+---------
> 1 | test
> (1 rows)
> ~/.ccm/test/node1/data0/test $ ccm node1 nodetool upgradesstables -- -a test
> drop_test
> ~/.ccm/test/node1/data0/test $ ls
> nb-2-big-CompressionInfo.db nb-2-big-Digest.crc32 nb-2-big-Index.db
> nb-2-big-Summary.db
> nb-2-big-Data.db nb-2-big-Filter.db nb-2-big-Statistics.db
> nb-2-big-TOC.txt
> ~/.ccm/test/node1/data0/test $ ~/.ccm/repository/5.0.3/tools/bin/sstabledump
> nb-2-big-Data.db
> [
> {
> "table kind" : "REGULAR",
> "partition" : {
> "key" : [ "1" ],
> "position" : 0
> },
> "rows" : [
> {
> "type" : "row",
> "position" : 18,
> "liveness_info" : { "tstamp" : "2025-11-05T20:32:17.946616Z" },
> "cells" : [
> { "name" : "message", "value" : "test" }
> ]
> }
> ]
> }
> ]%
> ~/.ccm/test/node1/data0/test $
> ~/.ccm/repository/5.0.3/tools/bin/sstablemetadata nb-2-big-Data.db | grep -E
> 'StaticColumns|RegularColumns'
> StaticColumns:
> RegularColumns: col_to_delete:org.apache.cassandra.db.marshal.UTF8Type,
> message:org.apache.cassandra.db.marshal.UTF8Type{noformat}
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