Set up docs MCPThese settings are available in system.settings and are autogenerated from source.
enable_parallel_blocks_marshalling
Version history
| Version | Default value | Comment |
|---|---|---|
| 25.6 | true | A new setting |
Affects only distributed queries. If enabled, blocks will be (de)serialized and (de)compressed on pipeline threads (i.e. with higher parallelism that what we have by default) before/after sending to the initiator.
enable_parallel_single_level_merge
Version history
| Version | Default value | Comment |
|---|---|---|
| 26.8 | 1 | New setting to parallelize the final merge of the single-level aggregation hash tables by splitting the key space into disjoint hash partitions that the threads merge independently. |
Parallelize the final merge of the per-thread single-level aggregation hash tables. The key space is split into disjoint partitions by key hash, and each partition is merged independently: the merging thread enumerates all per-thread tables and combines the keys that belong to its partition, so no two threads ever touch the same key. If the setting is turned off, the single-level tables are merged serially on one thread. Aggregation by 8- and 16-bit keys keeps its own range-partitioned parallel merge regardless of this setting.