> ## 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.

# check_* MergeTree table settings

> ClickHouse MergeTree table settings in the check_* 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="check_delay_period">
  check\_delay\_period
</h2>

<SettingsInfoBlock type="UInt64" default_value="60" />

Obsolete setting, does nothing.

<h2 id="check_sample_column_is_correct">
  check\_sample\_column\_is\_correct
</h2>

<SettingsInfoBlock type="Bool" default_value="1" />

Enables the check at table creation, that the data type of a column for s
ampling or sampling expression is correct. The data type must be one of unsigned
[integer types](/docs/reference/data-types/int-uint): `UInt8`, `UInt16`,
`UInt32`, `UInt64`.

Possible values:

* `true`  — The check is enabled.
* `false` — The check is disabled at table creation.

Default value: `true`.

By default, the ClickHouse server checks at table creation the data type of
a column for sampling or sampling expression. If you already have tables with
incorrect sampling expression and do not want the server to raise an exception
during startup, set `check_sample_column_is_correct` to `false`.