> ## 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_or_like_chain_* session settings

> ClickHouse session settings in the optimize_or_like_chain_* 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_or_like_chain">
  optimize\_or\_like\_chain
</h2>

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

<VersionHistory rows={[{"id": "row-1","items": [{"label": "26.7"},{"label": "1"},{"label": "Enable by default: optimize OR chains of LIKE\/ILIKE\/match into multiSearchAny (pure-substring patterns) or multiMatchAny (other patterns, when Hyperscan\/Vectorscan is permitted); when neither fast path applies the original OR chain is kept unchanged."}]}]} />

Optimize multiple `OR LIKE/ILIKE/match` predicates on the same expression into a single `multiSearchAny`/`multiSearchAnyCaseInsensitiveUTF8` (for pure-substring `%needle%` patterns) or `multiMatchAny` (for other patterns, when Hyperscan/Vectorscan is permitted). When neither fast path is applicable — for example when Hyperscan is disabled or unavailable, or the patterns are raw `match` regexps, not valid UTF-8, contain an embedded NUL, or the haystack is `FixedString`/`Enum` — the original `OR` chain is kept unchanged, because a combined `match` alternation over RE2 is consistently slower than the original short-circuit `OR`.

The optimization is applied only with the analyzer (`enable_analyzer = 1`, the default); with the old analyzer (`enable_analyzer = 0`) the `OR` chain is left unchanged. For pure `LIKE`/`ILIKE`/`match` `OR` chains the original expressions are preserved in `indexHint()` to allow index analysis; mixed `OR` chains that include non-`LIKE` branches intentionally skip `indexHint()` wrapping so that ranges matching only the non-`LIKE` branch are not pruned. The `multiMatchAny` rewrite honors `allow_hyperscan`, `max_hyperscan_regexp_length`, `max_hyperscan_regexp_total_length` and `reject_expensive_hyperscan_regexps`.

A chain is rewritten only when it has enough branches sharing the same left-hand-side expression to make the rewrite reliably faster than short-circuit `OR` evaluation: at least `optimize_or_like_chain_min_substrings` branches for the `multiSearchAny` path, and at least `optimize_or_like_chain_min_patterns` branches for the `multiMatchAny` path.

<h2 id="optimize_or_like_chain_min_patterns">
  optimize\_or\_like\_chain\_min\_patterns
</h2>

<SettingsInfoBlock type="UInt64" default_value="10" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "26.7"},{"label": "10"},{"label": "New setting controlling the minimum number of non-pure-substring LIKE\/ILIKE\/match branches (sharing the same LHS expression) required for optimize_or_like_chain to rewrite a chain into multiMatchAny. Shorter chains are kept as-is because the multiMatchAny (Hyperscan) rewrite only becomes faster than short-circuit OR evaluation from about nine branches."}]}]} />

Minimum number of non-pure-substring `LIKE`/`ILIKE`/`match` branches (prefix/suffix/regexp patterns), sharing the same left-hand-side expression, required for `optimize_or_like_chain` to rewrite a chain into `multiMatchAny`. Calibrated on the `hits` dataset (see `tests/performance/optimize_or_like_chain_hits.xml`): a `multiMatchAny` (Hyperscan) rewrite of prefix/regexp `LIKE` chains only becomes faster than short-circuit `OR` evaluation from about nine branches, so shorter chains are kept as-is to avoid regressing them. A value of 0 or 1 disables the threshold. Has no effect when `optimize_or_like_chain` is disabled. See also `optimize_or_like_chain_min_substrings` for the pure-substring (`multiSearchAny`) path.

<h2 id="optimize_or_like_chain_min_substrings">
  optimize\_or\_like\_chain\_min\_substrings
</h2>

<SettingsInfoBlock type="UInt64" default_value="4" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "26.7"},{"label": "4"},{"label": "New setting controlling the minimum number of pure-substring (%needle%) LIKE\/ILIKE branches (sharing the same LHS expression) required for optimize_or_like_chain to rewrite a chain into multiSearchAny."}]}]} />

Minimum number of pure-substring (`%needle%`) `LIKE`/`ILIKE` branches, sharing the same left-hand-side expression, required for `optimize_or_like_chain` to rewrite a chain into `multiSearchAny`/`multiSearchAnyCaseInsensitiveUTF8`. Calibrated on the `hits` dataset (see `tests/performance/optimize_or_like_chain_hits.xml`): the `multiSearchAny` rewrite becomes faster than short-circuit `OR` evaluation from about four branches. A value of 0 or 1 disables the threshold. Has no effect when `optimize_or_like_chain` is disabled. See also `optimize_or_like_chain_min_patterns` for the regexp (`multiMatchAny`) path.