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https://issues.apache.org/jira/browse/CASSANDRA-21000?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18038905#comment-18038905
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Stefan Miklosovic edited comment on CASSANDRA-21000 at 11/17/25 3:42 PM:
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I see it the same way, [~blambov], but then there is also this and I am not
sure what was meant by that (1). Why not to just take the current state of
columns in TableMetadata (as proposed in the patch) but we are instead of that
adding all columns from all SSTables we go to compact? That will also contain
the ones which were dropped in the meanwhile (as some SSTable to compact might
contain columns in its header which were dropped by the time we hit this code
execution).
EDIT: ah wait ... we iterate over SSTables like that because these SSTables do
not need to contain data for _current columns_.
SSTable1 - columns a, b, c
SSTAble 2 - columns a, b, c
ALTER TABLE add a column D
SSTable 3 - columns a, b, c, d
Then when that set of SSTables going into "make" method is just SSTable1 and 2,
then we do not want to use the latest columns for that table (a, b, c, d)
because SSTable 1 and 2 actually do not contain it.
(1)
https://github.com/apache/cassandra/blob/trunk/src/java/org/apache/cassandra/db/SerializationHeader.java#L93-L100
was (Author: smiklosovic):
I see it the same way, [~blambov], but then there is also this and I am not
sure what was meant by that (1). Why not to just take the current state of
columns in TableMetadata (as proposed in the patch) but we are instead of that
adding all columns from all SSTables we go to compact? That will also contain
the ones which were dropped in the meanwhile (as some SSTable to compact might
contain columns in its header which were dropped by the time we hit this code
execution).
(1)
https://github.com/apache/cassandra/blob/trunk/src/java/org/apache/cassandra/db/SerializationHeader.java#L93-L100
> 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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