> ## Documentation Index
> Fetch the complete documentation index at: https://filament.getgalaxy.io/llms.txt
> Use this file to discover all available pages before exploring further.

# PostgreSQL

> Write to PostgreSQL.

`connectors/postgres/sink` loads each resource into its own typed table with
native Postgres columns.

## Typed loading

The engine calls `EnsureSchema` once per resource before extraction, which
creates the destination table (adding any new columns to an existing one via
`ADD COLUMN IF NOT EXISTS`) and caches a prebuilt `INSERT` statement. `Write`
then casts each batch's JSON row payloads into those typed columns
server-side via `jsonb_to_recordset` — the batch is framed as one `jsonb`
array and expanded in a single statement rather than parsed and bound
row-by-row from the client.

## Write policies

A resumable ingestion type (`SnapshotUpsert`, `Upsert`) upserts by primary
key via `ON CONFLICT … DO UPDATE`, so a re-delivered row from an
at-least-once resume overwrites rather than errors on the unique
constraint. A non-resumable load truncates the table first and inserts
plain, for full-snapshot replace semantics.

## Modes

Supports `SnapshotReplace`, `SnapshotUpsert`, `Append`, and `Upsert` write
policies (see [Replication modes](/pages/guides/concepts/replication-modes)).
CDC lands through the [MySQL sink's](/pages/connectors/sinks/mysql) merge
path today; Postgres CDC write support is not yet implemented.