This patch avoids loading dictionaries for:
- SELECT * FROM system.tables (used by clickhouse-client for completion)
- SHOW CREATE TABLE some_dict
But the dictionary will still be loaded on:
- SHOW CREATE TABLE some_dict (from the database with Dictionary engine)
* "lock_acquire_timeout" controls for how long a query will continue to
acquire each lock on its argument tables
* "lock_acquire_timeout_for_background_operations" is a per-table
setting for storages of *MergeTree family