> ## Documentation Index
> Fetch the complete documentation index at: https://private-7c7dfe99-trino-dialect.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# deduplicate_insert_* session settings

> ClickHouse session settings in the deduplicate_insert_* generated group.

export const VersionHistory = ({rows = []}) => {
  if (rows.length === 0) {
    return null;
  }
  const headers = ["Version", "Default value", "Comment"];
  const border = "1px solid rgba(128, 128, 128, 0.3)";
  const cell = {
    border,
    padding: "0.25rem 0.5rem",
    textAlign: "start",
    verticalAlign: "top"
  };
  return <details className="not-prose" style={{
    border,
    borderRadius: "0.5rem",
    margin: "0.5rem 0",
    padding: "0.5rem 0.75rem",
    fontSize: "0.8125rem",
    lineHeight: "1.125rem"
  }}>
      <summary style={{
    cursor: "pointer",
    fontWeight: 600,
    opacity: 0.72
  }}>
        Version history
      </summary>
      <table style={{
    borderCollapse: "collapse",
    width: "100%",
    margin: "0.5rem 0 0"
  }}>
        <thead>
          <tr>
            {headers.map(header => <th key={header} style={{
    ...cell,
    fontWeight: 600,
    opacity: 0.72
  }}>
                {header}
              </th>)}
          </tr>
        </thead>
        <tbody>
          {rows.map((row, row_index) => <tr key={row.id ?? row_index}>
              {(row.items ?? []).map((item, item_index) => <td key={item_index} style={{
    ...cell,
    overflowWrap: "anywhere"
  }}>
                  {item?.label}
                </td>)}
            </tr>)}
        </tbody>
      </table>
    </details>;
};

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

<h2 id="deduplicate_insert">
  deduplicate\_insert
</h2>

<SettingsInfoBlock type="DeduplicateInsertMode" default_value="enable" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "26.2"},{"label": "enable"},{"label": "Enable deduplication for all sync and async inserts by default."}]}]} />

Enables or disables block deduplication of  `INSERT INTO` (for Replicated\* tables).
The setting applies to both synchronous and asynchronous inserts, and it supersedes the `insert_deduplicate` and `async_insert_deduplicate` settings.
That setting has three possible values:

* disable — Deduplication is disabled for `INSERT INTO` query.
* enable — Deduplication is enabled for `INSERT INTO` query.
* backward\_compatible\_choice — Deduplication is enabled if `insert_deduplicate` or `async_insert_deduplicate` are enabled for specific insert type.

For `INSERT SELECT` queries, [`deduplicate_insert_select`](/reference/settings/session-settings/deduplicate-insert#deduplicate_insert_select) is consulted first. Deduplication also requires the destination table to keep a deduplication log, see [replicated\_deduplication\_window](/reference/settings/merge-tree-settings/replicated-deduplication-window#replicated_deduplication_window) and [non\_replicated\_deduplication\_window](/reference/settings/merge-tree-settings/other#non_replicated_deduplication_window).

<h2 id="deduplicate_insert_select">
  deduplicate\_insert\_select
</h2>

<SettingsInfoBlock type="DeduplicateInsertSelectMode" default_value="enable_when_possible" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "26.1"},{"label": "enable_when_possible"},{"label": "change the default behavior of deduplicate_insert_select to ENABLE_WHEN_POSSIBLE"}]}, {"id": "row-2","items": [{"label": "25.12"},{"label": "enable_even_for_bad_queries"},{"label": "New setting, replace insert_select_deduplicate"}]}]} />

Enables or disables block deduplication of `INSERT SELECT` (for Replicated\* tables).
For `INSERT SELECT` queries this setting is consulted before [`deduplicate_insert`](/reference/settings/session-settings/deduplicate-insert#deduplicate_insert).
A `SELECT` is stable when it carries `ORDER BY ALL` and its pipeline ends in a single stream. A non-empty [`insert_deduplication_token`](/reference/settings/session-settings/insert#insert_deduplication_token) is an equivalent substitute for stability.
That setting has four possible values:

* disable — Deduplication is disabled for `INSERT SELECT` query.
* force\_enable — Deduplication is enabled for `INSERT SELECT` query, regardless of `deduplicate_insert`. If select result is not stable and no token is provided, exception is thrown.
* enable\_when\_possible — Deduplication is enabled if it is enabled by `deduplicate_insert` and the select result is stable, otherwise disabled.
* enable\_even\_for\_bad\_queries - Deduplication is enabled if it is enabled by `deduplicate_insert`, regardless of whether the select result is stable. If select result is not stable, a message is logged, but query is executed with deduplication. This option is for backward compatibility. Consider to use other options instead as it may lead to unexpected results.