group_by_overflow_mode
Sets what happens when the number of unique keys for aggregation exceeds the limit:throw: throw an exceptionbreak: stop executing the query and return the partial resultany: continue aggregation for the keys that got into the set, but do not add new keys to the set.
group_by_two_level_threshold
From what number of keys, a two-level aggregation starts. 0 - the threshold is not set.group_by_two_level_threshold_bytes
From what size of the aggregation state in bytes, a two-level aggregation begins to be used. 0 - the threshold is not set. Two-level aggregation is used when at least one of the thresholds is triggered.group_by_use_nulls
Changes the way the GROUP BY clause treats the types of aggregation keys. When theROLLUP, CUBE, or GROUPING SETS specifiers are used, some aggregation keys may not be used to produce some result rows.
Columns for these keys are filled with either default value or NULL in corresponding rows depending on this setting.
Possible values:
- 0 — The default value for the aggregation key type is used to produce missing values.
- 1 — ClickHouse executes
GROUP BYthe same way as the SQL standard says. The types of aggregation keys are converted to Nullable. Columns for corresponding aggregation keys are filled with NULL for rows that didn’t use it.