---
title: Faster BM25 Queries
description: Speed up queries that return the most relevant results
canonical: https://www.paradedb.com/docs/reference/indexing/faster-bm25-queries
---

<Note>This feature is available in versions `0.26.0` and above.</Note>

Top K queries ordered by
[BM25 score](/reference/full-text/score) can be sped up by setting `pnorms=true`
when creating your index, at the cost of a larger index and longer builds.

## Enable the Optimization

Set `pnorms=true` on the [tokenizer](/reference/tokenizers/overview) cast for each
text field used in BM25 scoring. The option defaults to `false`. This example
enables it for `description`:

```sql
CREATE INDEX search_idx ON mock_items
USING paradedb (id, (description::pdb.unicode_words('pnorms=true')), category)
WITH (key_field = 'id');
```

Queries automatically use the setting from the index:

```sql
SELECT id, description, pdb.score(id)
FROM mock_items
WHERE description ||| 'shoes'
ORDER BY pdb.score(id) DESC
LIMIT 5;
```

This option is only supported for text fields. Existing indexes must be
[rebuilt](/operate/index-maintenance/reindexing) with `pnorms=true` to enable it.

## Performance Tradeoff

BM25 scoring uses the length of each text field to help determine relevance.
Setting `pnorms=true` stores an extra, denser copy of this information where the scoring
process can read it more efficiently. Depending on the data and query, this can
make queries several times faster without changing scores or relevance ranking.

For each field with `pnorms` enabled, the extra storage is roughly one byte per
distinct term in each document, plus metadata. The extra data also increases
the work required to build and merge index segments. Enable `pnorms` on fields
where faster BM25 top K queries justify those costs.