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

# optimize_move_to_prewhere_* session settings

> ClickHouse session settings in the optimize_move_to_prewhere_* 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="optimize_move_to_prewhere">
  optimize\_move\_to\_prewhere
</h2>

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

Enables or disables automatic [PREWHERE](/reference/statements/select/prewhere) optimization in [SELECT](/reference/statements/select/index) queries.

Works only for [\*MergeTree](/reference/engines/table-engines/mergetree-family/index) tables.

Possible values:

* 0 — Automatic `PREWHERE` optimization is disabled.
* 1 — Automatic `PREWHERE` optimization is enabled.

<h2 id="optimize_move_to_prewhere_if_final">
  optimize\_move\_to\_prewhere\_if\_final
</h2>

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

<VersionHistory rows={[{"id": "row-1","items": [{"label": "26.10"},{"label": "1"},{"label": "Enable the automatic PREWHERE optimization for queries with FINAL by default. Only conditions that depend on the sorting key alone and are deterministic within the query are moved, so results are not affected. `compatibility` below 26.10 restores the previous behavior."}]}]} />

Enables or disables automatic [PREWHERE](/reference/statements/select/prewhere) optimization in [SELECT](/reference/statements/select/index) queries with [FINAL](/reference/statements/select/from#final-modifier) modifier.

Only conditions that depend on the sorting key alone and are deterministic within the query are moved,
so the result of `FINAL` is not affected.

Works only for [\*MergeTree](/reference/engines/table-engines/mergetree-family/index) tables.

Possible values:

* 0 — Automatic `PREWHERE` optimization in `SELECT` queries with `FINAL` modifier is disabled.
* 1 — Automatic `PREWHERE` optimization in `SELECT` queries with `FINAL` modifier is enabled.

**See Also**

* [optimize\_move\_to\_prewhere](/reference/settings/session-settings/optimize-move-to-prewhere#optimize_move_to_prewhere) setting