lancedb/docs/web/sql/dql/duplicate-pairs.mdx

---
title: "DUPLICATE_PAIRS"
sidebarTitle: "DUPLICATE_PAIRS"
description: "The duplicate_pairs() table function: every close pair in a vector column, scanned over the index."
icon: clone
keywords: ["duplicate_pairs", "vector_duplicate_pairs", "sql", "deduplication", "near-duplicate", "table function"]
availability:
  embedded: unavailable
  enterprise: available
---

`duplicate_pairs` scans a vector column's [index](/indexing/vector-index)
partitions for every pair of rows closer than a distance threshold, without a
full pairwise scan or a shuffle. It returns one row per close pair, not one
row per source row -- use it to inspect what would be collapsed before
committing to [`dedupe`](/sql/dql/dedupe), which resolves these same pairs
into groups.

<CodeGroup>
```sql SQL icon="database"
SELECT * FROM duplicate_pairs(
    <table>,
    <vector_column>,
    distance_threshold => <float>
    [, id_column => <column>]
    [, selection => 'all' | 'first' | 'random', count => <int>, seed => <int>]
)
```
</CodeGroup>

<CodeGroup>
```sql SQL icon="database"
SELECT * FROM duplicate_pairs(
    'frames',
    'vec',
    distance_threshold => 0.02
)
```
</CodeGroup>

<Note>
Earlier releases spelled this `vector_duplicate_pairs`; that name is rejected
on current deployments.
</Note>

## Input {#input}

| Argument | Type | Required | Meaning |
| --- | --- | --- | --- |
| table name | string literal | yes | the table to scan |
| vector column | string literal | yes | the indexed vector column to compare |
| `distance_threshold` | float | yes | maximum distance for a pair to count as close |
| `id_column` | column name | no | project this column's value instead of the internal row ID -- see [Application-level identifiers](#id-column) |
| `selection` | `'all'` (default) \| `'first'` \| `'random'` | no | which index partitions to scan |
| `count` | int | no | number of partitions to sample when `selection => 'random'` |
| `seed` | int | no | random seed when `selection => 'random'` |

`resolution` is refused on `duplicate_pairs`: a pair has no notion of a group,
only [`dedupe`](/sql/dql/dedupe#input) accepts it.

## Output {#output}

One row per close pair found, in a fixed schema independent of the source
table:

| Column | Type | Meaning |
| --- | --- | --- |
| `row_id_a` | uint64 | internal row ID of the first row in the pair, the same identifier as the [`_rowid`](/sql/data-types#pseudo-columns) pseudo-column |
| `row_id_b` | uint64 | internal row ID of the second row in the pair |
| `distance` | float32 | distance between the pair's vectors, at or below `distance_threshold`. For `l2`, this is the squared distance, not its square root |
| `segment_id` | Utf8 | which index segment the pair was found in, a UUID |
| `partition_id` | uint64 | which index partition the pair was found in |
| `dataset_version` | uint64 | the dataset version the scan ran against |

### Application-level identifiers {#id-column}

A row ID is internal and not stable across compaction. Pass `id_column`, a
top-level scalar column such as a primary key, to also project its value:
`id_a`/`id_b`, typed like `id_column`, are appended alongside
`row_id_a`/`row_id_b`, which remain in the output.

<CodeGroup>
```sql SQL icon="database"
SELECT * FROM duplicate_pairs(
    'frames',
    'vec',
    distance_threshold => 0.02,
    id_column => 'frame_id'
)
```
</CodeGroup>

## Sampling partitions {#sampling}

`selection` scopes the scan to a sample of partitions instead of all of them,
the same `all` (default) / `first` / `random` choice as
[`ivf_partition`](/sql/dql/ivf-partition). Use it to estimate a
distance threshold or duplicate rate on a large table before scanning it in
full:

<CodeGroup>
```sql SQL icon="database"
SELECT * FROM duplicate_pairs(
    'frames',
    'vec',
    distance_threshold => 0.02,
    selection => 'random',
    count => 100,
    seed => 42
)
```
</CodeGroup>

## What to read next {#next}

<CardGroup cols={2}>
  <Card title="DEDUPE" icon="layer-group" href="/sql/dql/dedupe">
    Resolve these same pairs into one representative row per group.
  </Card>
  <Card title="Deduplicate near-duplicates" icon="copy" href="/curation/dedupe">
    When to reach for this instead of exact-key deduplication.
  </Card>
</CardGroup>