> ## Documentation Index
> Fetch the complete documentation index at: https://paradedb-ankitml-legacy-docs-remove.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Create an Index

> Index a Postgres table for full text search

Before a table can be searched, it must be indexed. ParadeDB uses a custom index type called the BM25 index.
The following code block creates a BM25 index over several columns in the `mock_items` table.

```sql theme={null}
CREATE INDEX search_idx ON mock_items
USING bm25 (id, description, category)
WITH (key_field='id');
```

By default, text columns are tokenized using the [unicode](/documentation/tokenizers/available-tokenizers/unicode) tokenizer, which splits text according to the
Unicode segmentation standard. Because index creation is a time-consuming operation, we recommend experimenting with the [available tokenizers](/documentation/tokenizers/overview)
to find the most suitable one before running `CREATE INDEX`.

For instance, if a column contains multiple languages, the ICU tokenizer may be more appropriate.

```sql theme={null}
CREATE INDEX search_idx ON mock_items
USING bm25 (id, (description::pdb.icu), category)
WITH (key_field='id');
```

Only one BM25 index can exist per table. We recommend indexing all columns in a table that may be present in a search query,
including columns used for sorting, grouping, filtering, and aggregations.

```sql theme={null}
CREATE INDEX search_idx ON mock_items
USING bm25 (id, description, category, rating, in_stock, created_at, metadata, weight_range)
WITH (key_field='id');
```

Most Postgres types, including text, JSON, numeric, timestamp, range, boolean, and arrays, can be indexed.

## Track Create Index Progress

To monitor the progress of a long-running `CREATE INDEX`, open a separate Postgres connection and query `pg_stat_progress_create_index`:

```sql theme={null}
SELECT pid, phase, blocks_done, blocks_total
FROM pg_stat_progress_create_index;
```

Comparing `blocks_done` to `blocks_total` will provide a good approximation of the progress so far. If `blocks_done` equals
`blocks_total`, that means that all rows have been indexed and the index is being flushed to disk.

## Choosing a Key Field

In the `CREATE INDEX` statement above, note the mandatory `key_field` option.
Every BM25 index needs a `key_field`, which is the name of a column that will function as a row’s unique identifier within the index.

The `key_field` must:

1. Have a `UNIQUE` constraint. Usually this means the table's `PRIMARY KEY`.
2. Be the first column in the column list.
3. Be untokenized, if it is a text field.

## Token Filters

After tokens are created, [token filters](/documentation/token-filters/overview) can be configured to apply further processing like lowercasing, stemming, or unaccenting.
For example, the following code block adds English stemming to `description`:

```sql theme={null}
CREATE INDEX search_idx ON mock_items
USING bm25 (id, (description::pdb.simple('stemmer=english')), category)
WITH (key_field='id');
```