Create PostgreSQL Materialization

Create a PostgreSQL materialization using flowctl to stream data from Estuary collections into PostgreSQL tables.

Applies to: materialize-postgres (all variants: vanilla, RDS, Aurora, Cloud SQL, Supabase, AlloyDB, Neon)

Step 0: Load Connector Documentation

Before proceeding, fetch the official connector docs for prerequisites, config reference, and setup instructions.

Load the docs page: https://docs.estuary.dev/reference/Connectors/materialization-connectors/PostgreSQL/

Use WebFetch to load this page. It covers:

• Prerequisites (user creation, permissions, schema setup)
• Full config property reference
• SSH tunnel configuration
• SSL configuration
• Advanced options (delta updates, hard deletes, sync schedule)

Search Kapa for tribal knowledge (if the Estuary MCP is configured):

Search kapa ai knowledge sources for "materialize postgres common issues"

If Kapa MCP is not configured, the user can set it up: https://docs.estuary.dev/features/mcp-integration/

This skill provides the flowctl workflow and troubleshooting that docs don't cover.

Step 1: Gather Requirements

Before writing any YAML, ask the user:

1. Postgres variant? — Vanilla, RDS, Aurora, Cloud SQL, Supabase, AlloyDB
2. Network path? — Direct connection (cloud-hosted with IP allowlist), SSH tunnel (private network/on-prem), or ngrok (local dev). Connection poolers are NOT supported. If the user mentions Supabase, Neon, PgBouncer, or PgCat, warn them immediately:
   • The connector uses session-level temporary tables and prepared statements that break with pooled connections.
   • Supabase: Must use the Direct connection (db.xxx.supabase.co:5432), not the pooler (xxx.pooler.supabase.com:6543).
   • Neon: Must use the non-pooler endpoint — remove -pooler from the hostname.
3. Non-default data plane? — Most users use the default. Ask if they need a non-default data plane.
4. Target database and schema? — Database name, schema (default: public)
5. Source collections? — Which Estuary collections to materialize
6. SSL required? — Some cloud providers require SSL connections
7. Hard deletes? — Off by default. Without it, deleted rows stay in the destination marked with _meta/op: 'd'. Enable to physically remove them.
8. Delta updates? — Off by default. Switches from one-row-per-key (standard merge) to append-only. Use for event logs or history tables.
9. Sync schedule? — Controls how often batches are written to the destination (default: 30 minutes, 0s for real-time). Affects latency and destination compute cost.

Step 2: Find the Correct Connector Version

Always use the latest numbered version tag. Query the connector registry:

flowctl raw get --table connector_tags \
  --query 'documentation_url=eq.https://go.estuary.dev/materialize-postgres' \
  --query 'select=image_tag,documentation_url' \
  --output yaml

Use the returned image_tag — never hardcode a version.

Step 3: Help User Complete Prerequisites

Walk the user through prerequisites from the docs loaded in Step 0:

1. Database user — Create a user with write permissions on the target schema
2. Schema permissions — USAGE and CREATE on target schema
3. Table permissions — SELECT, INSERT, UPDATE, DELETE if materializing to existing tables
4. Network access — Firewall rules or SSH tunnel configured

Refer to the docs page for exact SQL commands and cloud-specific instructions.

Step 4: Create the Spec File

Build flow.yaml using the config reference from the docs. Minimal required config:

materializations:
  <TENANT>/<PATH>/materialize-postgres:
    endpoint:
      connector:
        image: ghcr.io/estuary/materialize-postgres:<VERSION>
        config:
          address: "<HOST>:5432"
          database: "<DATABASE>"
          user: "<USERNAME>"
          password: "<PASSWORD>"
          schema: "<SCHEMA>"
    bindings:
      - source: <TENANT>/<collection-path>
        resource:
          table: "<TABLE_NAME>"

For SSH tunnel or SSL, add the appropriate config block — see docs for full reference.

Step 5: Publish

flowctl catalog publish --source flow.yaml --auto-approve

Step 6: Verify

# Check status
flowctl catalog status <TENANT>/<PATH>/materialize-postgres

# View logs
flowctl logs --task <TENANT>/<PATH>/materialize-postgres --since 5m | jq -c '{ts, message}'

Status progression:

1. PENDING — Normal for ~30 seconds during shard assignment
2. BACKFILLING — Initial data sync from collection
3. OK — Running normally with real-time updates

Troubleshooting

"connection refused" or timeout

Cause: Database not reachable from Estuary cloud

Fix:

1. Verify firewall allows Estuary IP addresses (see docs)
2. Check security groups (AWS) or firewall rules (GCP)
3. Use SSH tunnel for private databases
4. For local testing: ngrok tcp 5432

"password authentication failed"

Cause: Incorrect credentials or user doesn't exist

Fix:

1. Verify username and password
2. Check user exists: SELECT * FROM pg_user WHERE usename = '<user>';
3. Verify user can connect from external hosts (check pg_hba.conf)

"permission denied for schema"

Cause: User lacks permissions on target schema

Fix: Grant USAGE and CREATE on the target schema — see docs for SQL.

"relation already exists" or schema conflicts

Cause: Table already exists with incompatible schema

Fix:

1. Drop and recreate the table
2. Use a different table name
3. Ensure collection schema matches existing table

Materialization stuck in PENDING

Wait 30-60 seconds — this is normal during shard assignment. If still stuck:

flowctl logs --task <TENANT>/<PATH>/materialize-postgres --since 5m | jq 'select(.level == "error")'

SSL connection errors

Cause: SSL mode mismatch or certificate issues

Fix:

1. Try sslmode: "require" first
2. For AWS RDS, SSL is usually required — use verify-ca or verify-full
3. For self-signed certs, use require mode
4. See docs for full SSL configuration options

SSH tunnel connection failures

Cause: SSH configuration issues

Fix:

1. Verify bastion is reachable: ssh -p 22 user@bastion
2. Check private key format (must be OpenSSH format)
3. Verify bastion can reach database: nc -zv db-host 5432
4. See SSH tunnel troubleshooting docs

Related Skills

• connector-disable-enable — Pause/restart existing materializations
• connector-delete-recreate — Nuclear option for stuck materializations
• estuary-logs — Deep log analysis
• estuary-catalog-status — Status checking