400 indexes on empty buckets consumes 5 cores without obvious reason

indexing SHA: 6f5e5abed8adf4f51562cedd4ce0a65a68bad824
kv SHA: b27ef1facb5d6237d870deae8100a3b44299749b
ns_server SHA: 357af870e881218315e112332a66e9cb0ad45a33

1 node cluster started by cluster_run,
1 empty bucket: test1,
400 indexes created by the following command:

$ for i in {1..400}; do time ./cbq -u Administrator -p asdasd -engine=http://127.0.0.1:9000/ -script "create index index${i} on \`test1\`(address)"; done

When creation is finished, it can be seen that the indexer process consumes 500-600% CPU (see htop screenshot).
Logs are attached.