How to rename keyspace in Apache Cassandra 4

Renaming keyspaces (and column families) is no supported in Apache Cassandra version 4. But if you need it, you can make a keyspace clone and delete old keyspce instead rename. This story was made by this answer on stack-overflow.

Steps to clone keyspace:

1 — Export the schema from the old keyspace to a file

/opt/cassandra/bin/cqlsh ip_cassandra -u user -p password -e "DESCRIBE keyspace_name;" > old_keyspace.cql

2 — Replace the keyspace name in the file to new keyspace

3 — Apply the schema to the new keyspace (and the keyspace itself) from the file

/opt/cassandra/bin/cqlsh ip_cassandra -u user -p password -f old_keyspace.cql

4 — Clear snapshots on each node

nodetool clearsnapshot --all

5 — Take snapshots from the old keyspace on each node

nodetool flush
nodetool snapshot -t clone old_keyspace

6 — Move the snapshots to the table folders in the new keyspace (see script bellow) on each node

sudo sh clone.sh old_keyspace new_keyspace

There is a code of clone.sh script:

#!/bin/bash

if [ "$#" -ne 2 ]; then
    echo "Usage: $0 keyspace_from keyspace_to"
    exit 1
fi
    
keyspace_from=$1
keyspace_to=$2
     
for src_table_dir in /data/cassandra/data/$keyspace_from/*-*
    do
      src_table=$(basename $src_table_dir)
      table=$(echo $src_table | cut -d "-" -f 1)
    
      if [ ! -d $src_table_dir/snapshots/clone ]; then
        echo "NO SNAPSHOTS DIRECTORY IN $src_table_dir, SKIPPING..."
        continue
      fi

      dest_table_dir=$(find /data/cassandra/data/$keyspace_to/ -maxdepth 1 -type d -name "$table-*")

      if [ ! -d $dest_table_dir ]; then
        echo "Destination table directory for $table does not exist in $keyspace_to, creating it..."
        continue
      fi

      echo "Moving snapshots from $src_table_dir/snapshots to $dest_table_dir..."
      for file in "$src_table_dir"/snapshots/clone/*; do
        if [ -f "$file" ]; then
          mv "$file" "$dest_table_dir/"
        fi
      done

      mv $src_table_dir/snapshots/copy/* $dest_table_dir/
    
      if [ $? -ne 0 ]; then
        echo "Error during copying, exiting..."
        exit 1
      fi
    done

echo "The clonning process done."

7 — Restart Cassandra on each node

sudo systemctl restart cassandra