> ## 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.

# max_parts_* MergeTree table settings

> ClickHouse MergeTree table settings in the max_parts_* 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.merge\_tree\_settings](/docs/reference/system-tables/merge_tree_settings) and are autogenerated from ClickHouse source.

<h2 id="max_parts_in_total">
  max\_parts\_in\_total
</h2>

<SettingsInfoBlock type="UInt64" default_value="100000" />

If the total number of active parts in all partitions of a table exceeds the
`max_parts_in_total` value `INSERT` is interrupted with the `Too many parts
(N)` exception.

Possible values:

* Any positive integer.

A large number of parts in a table reduces performance of ClickHouse queries
and increases ClickHouse boot time. Most often this is a consequence of an
incorrect design (mistakes when choosing a partitioning strategy - too small
partitions).

<h2 id="max_parts_to_merge_at_once">
  max\_parts\_to\_merge\_at\_once
</h2>

<SettingsInfoBlock type="UInt64" default_value="100" />

Max amount of parts which can be merged at once (0 - disabled). Doesn't affect
OPTIMIZE FINAL query.