> ## Documentation Index
> Fetch the complete documentation index at: https://clickhouse.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# partial_merge_* session settings

> ClickHouse session settings in the partial_merge_* generated group.

export const SettingsInfoBlock = ({type, default_value, changeable_without_restart}) => {
  return <div className="not-prose" style={{
    display: "flex",
    flexWrap: "wrap",
    alignItems: "baseline",
    columnGap: "0.5rem",
    rowGap: "0.125rem",
    margin: "0.375rem 0",
    fontSize: "0.8125rem",
    lineHeight: "1.125rem"
  }}>
      <div style={{
    fontWeight: 600,
    opacity: 0.72
  }}>Type</div>
      <div style={{
    overflowWrap: "anywhere"
  }}>{type}</div>
      <div style={{
    fontWeight: 600,
    opacity: 0.72,
    marginInlineStart: "0.5rem"
  }}>Default</div>
      <div style={{
    overflowWrap: "anywhere"
  }}>{default_value}</div>
      {changeable_without_restart && <div style={{
    fontWeight: 600,
    opacity: 0.72,
    marginInlineStart: "0.5rem"
  }}>
          Changeable without restart
        </div>}
      {changeable_without_restart && <div style={{
    overflowWrap: "anywhere"
  }}>
          {changeable_without_restart}
        </div>}
    </div>;
};

These settings are available in [system.settings](/docs/reference/system-tables/settings) and are autogenerated from [source](https://github.com/ClickHouse/ClickHouse/blob/master/src/Core/Settings.cpp).

<h2 id="partial_merge_join_left_table_buffer_bytes">
  partial\_merge\_join\_left\_table\_buffer\_bytes
</h2>

<SettingsInfoBlock type="UInt64" default_value="0" />

If not 0 group left table blocks in bigger ones for left-side table in partial merge join. It uses up to 2x of specified memory per joining thread.

<h2 id="partial_merge_join_rows_in_right_blocks">
  partial\_merge\_join\_rows\_in\_right\_blocks
</h2>

<SettingsInfoBlock type="UInt64" default_value="65536" />

Limits sizes of right-hand join data blocks in partial merge join algorithm for [JOIN](/docs/reference/statements/select/join) queries.

ClickHouse server:

1. Splits right-hand join data into blocks with up to the specified number of rows.
2. Indexes each block with its minimum and maximum values.
3. Unloads prepared blocks to disk if it is possible.

Possible values:

* Any positive integer. Recommended range of values: \[1000, 100000].