> ## Documentation Index
> Fetch the complete documentation index at: https://www.paradedb.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# How the ParadeDB Index Works

> Understand the index structures ParadeDB adds to Postgres

The ParadeDB index is a Postgres index access method designed for search and
analytics workloads. It stores several purpose-built structures together so one
index can serve full-text search, vector search, filtering, sorting, joins, and
aggregations.

## One Index, Multiple Structures

Each ParadeDB index is built from segment-local structures:

* **Inverted index** for tokenized text search and BM25 scoring.
* **Columnar storage** for scalar values used in filters, sorting, grouping,
  and aggregates.
* **Vector structures** for nearest-neighbor retrieval over pgvector `vector`
  columns.

Keeping these structures together is what lets ParadeDB compose workloads that
usually require separate systems or separate indexes. A query can match text,
restrict by scalar filters, retrieve vectors, and aggregate results without
shipping data out of Postgres.

## Segments and Writes

ParadeDB uses a log-structured layout. Incoming writes are added to a mutable
segment as part of the current Postgres transaction. When that segment reaches
the configured size, it becomes immutable and is later merged with other
segments.

This layout is optimized for update-heavy tables because writes are appended
instead of constantly rewriting one large index structure. Each immutable
segment carries its own inverted, columnar, and vector data.

## Query Execution

ParadeDB queries run through Postgres' planner and executor. When a supported
query uses a ParadeDB operator and a matching ParadeDB index exists, ParadeDB
can install a custom scan node and push eligible work into the index.

That pushed-down work can include text predicates, filters, Top K ordering,
aggregates, joins, and vector retrieval. If a query does not contain a ParadeDB
operator, Postgres executes it through its ordinary planning paths.

Use `EXPLAIN` to check which path a query takes. A ParadeDB-accelerated query
will show a custom scan, or in narrower cases a ParadeDB index scan.

## Related Reference

* [Create an Index](/docs/reference/indexing/create-index) covers index syntax and
  framework examples.
* [Columnar Storage](/docs/reference/indexing/columnar) covers fields used for
  filters, sorting, grouping, and aggregates.
* [Indexing Vectors](/docs/reference/indexing/indexing-vectors) covers vector fields
  inside the ParadeDB index.