> ## 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.

# optimize_move_to_prewhere_* session settings

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

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

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

Works only for [\*MergeTree](/docs/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="0" />

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

Works only for [\*MergeTree](/docs/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](/docs/reference/settings/session-settings/optimize-move-to-prewhere#optimize_move_to_prewhere) setting