These settings are available in system.merge_tree_settings and are autogenerated from ClickHouse source.
index_granularity
Type
UInt64
Default
8192
Maximum number of data rows between the marks of an index. I.e how many rows correspond to one primary key value.
index_granularity_bytes
Type
UInt64
Default
10485760
Maximum size of data granules in bytes.
To restrict the granule size only by number of rows, set to 0 (not recommended).