Removes an existing index from a column of type symbol.
Backup your database to avoid unintended data loss.
Removing an index is an atomic, non-blocking, and non-waiting operation. Once the operation is completed, the SQL engine stops using the index for SQL executions, and all its associated files are deleted.
This operation is similar to:
column is a symbol column that has an index
before the operation, and no index afterwards. Readers of the table might be
using the index in transaction A, in the meantime, a writer creates transaction
B containing the new version of the column, minus the index (metadata is set to
not have index, and index files are not copied across to the newer version).
When the readers are finished, QuestDB automatically deletes all the files
pertaining to the version of the column in transaction A (QuestDB uses hardlinks
internally to avoid an actual copy operation of the data files, as they do not
change at all).