elasticsearch · suggest

Did you mean

The term suggester corrects a word against the vocabulary actually indexed in a field. Use it when a search returns nothing, to offer the spelling that would have worked.

Ask for a correction

await es.search({
  index: 'shop.products', size: 0,
  suggest: {
    did_you_mean: { text: 'marathn', term: { field: 'name' } }
  }
})

// suggest.did_you_mean[0]
//   text: 'marathn', offset: 0, length: 7
//   options: [ { text: 'marathon', score: 0.857 } ]

Each entry is one word of your input, with its offset and length so you can splice a correction back into the original string. Options come back best first; the score is one minus the edit distance over the word length.

Correct every word, or only unknown ones

suggest_mode defaults to missing: a word the index already holds gets no options, which is what a search box wants. always returns near neighbours even for a word that exists, which is what you want for query expansion.

term: { field: 'name', suggest_mode: 'always', size: 3 }

A search box, end to end

Run the search; if it returns nothing, ask for a correction and offer it.

const res = await es.search({ index: 'shop.products',
  query: { match: { name: q } },
  suggest: { fix: { text: q, term: { field: 'name' } } }
})

if (res.hits.total.value === 0) {
  const best = res.suggest.fix[0]?.options[0]?.text
  if (best) console.log(`Did you mean ${best}?`)
}

What it does not return

no document frequency

Elasticsearch puts a freq on every option. That number lives somewhere this API cannot reach, so the field is omitted rather than invented. If you rank suggestions yourself, rank on score. For the same reason suggest_mode: popular, which is defined by frequency, is refused.

The phrase and completion suggesters are refused by name — there is no executor for either, and a silent empty result would read as "no suggestions" rather than "not supported".

Fuzzy matching

Typo tolerance inside the query itself, rather than as a correction.

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