Dictionary Diagnostics
Analyze external dictionaries: configuration, memory usage, reload status, and performance.
Diagnostics
Run all queries from the file checks.sql and analyze the results.
Dictionary Reload Operations
Force Reload (syntax reference)
-- SYSTEM RELOAD DICTIONARY {database}.{name}
-- SYSTEM RELOAD DICTIONARIES
Check Reload Result for Specific Dictionary
-- Check reload result
select
name,
status,
loading_start_time,
loading_duration,
last_exception
from system.dictionaries
where name = '{dictionary_name}'
Best Practices
Dictionary Sizing Guidelines
| Elements | Recommended Type |
|---|
| < 100K | Flat (if sequential keys) |
| 100K - 10M | Hashed |
| > 10M | Consider partitioning or cache |
| Complex keys | ComplexKeyHashed |
| Sparse access | Cache with SSD |
Common Issues
| Symptom | Cause | Solution |
|---|
| High memory | Too many elements | Use cache type, filter data |
| Slow reload | Large source table | Add filters, use delta updates |
| Stale data | Source unreachable | Check connectivity, add retry |
| Failed status | Source query fails | Check source table/query |
Cross-Module Triggers
| Finding | Load Module | Reason |
|---|
| High memory usage | altinity-expert-clickhouse-memory | Overall memory analysis |
| Load failures | altinity-expert-clickhouse-overview | Error summary + routing |
| Source connectivity | altinity-expert-clickhouse-logs | Log investigation |
| Slow lookups | altinity-expert-clickhouse-reporting | Query optimization |
Settings Reference
| Setting | Notes |
|---|
dictionaries_lazy_load | Load on first access vs startup |
dictionary_load_wait_timeout_ms | Wait time for lazy load |
max_dictionary_num_to_warn | Warning threshold |
