PostgreSQL wire

The PostgreSQL wire frontend lets Postgres clients that work in simple-query mode (psql, many JDBC/Python drivers in autocommit/simple mode, etc.) connect to QueryFlux over the PostgreSQL v3 wire protocol. Queries are executed synchronously — the TCP connection stays open while the result streams back as standard Postgres wire messages.

Configuration

queryflux:
  frontends:
    postgresWire:
      enabled: true
      port: 5432

Config key: postgresWire. Protocol identifier: FrontendProtocol::PostgresWire. Default dialect: SqlDialect::Postgres.

Protocol support

Feature	Status
Startup (protocol version 3.0)	Supported
Simple query (Q message)	Supported
Extended query (Parse/Bind/Execute)	Not supported — returns error
SSL negotiation	Declined (N response) — plaintext only
COPY protocol	Not supported

QueryFlux responds to the SSL request with N (no SSL), then processes the normal startup sequence. Clients that require TLS will need to connect without it or use an external TLS terminator.

Startup and authentication

1. Client sends StartupMessage with user, database, and optional parameters.
2. QueryFlux extracts credentials from the startup user field and authenticates via the configured auth_provider.
3. On success, QueryFlux sends AuthenticationOk, followed by ParameterStatus messages (server version 16.0-queryflux, encoding UTF8, etc.), BackendKeyData, and ReadyForQuery.

Execution model

All queries execute synchronously via execute_to_sink. Results stream as standard Postgres wire messages:

1. RowDescription — column metadata (names, types, format codes).
2. DataRow messages — one per row, text-format values.
3. CommandComplete — summary (e.g. SELECT 3).
4. ReadyForQuery — ready for the next query.

Errors are returned as Postgres ErrorResponse messages with SQLSTATE codes.

Session context

The Postgres wire frontend populates SessionContext as follows:

Field	Source
user	Startup message user parameter
database	Startup message database parameter
tags	query_tags / query_tag startup parameters
extra	Empty (startup parameters beyond user/database/query_tags are not forwarded)

The database and user fields are available to routers via ctx["database"] and ctx["user"] in the pythonScript router.

SET handling

SET statements are acknowledged with CommandComplete + ReadyForQuery without forwarding to the backend. This keeps the connection in a valid state for clients that issue SET during startup.

Client examples

# psql
psql -h localhost -p 5432 -U dev -d my_catalog -c "SELECT 1"

# Python (psycopg2)
import psycopg2
conn = psycopg2.connect(host="localhost", port=5432, user="dev", dbname="my_catalog")
cur = conn.cursor()
cur.execute("SELECT 42 AS answer")
print(cur.fetchone())

Not supported / Known limitations

Feature	Status
Extended query protocol (Parse/Bind/Execute/Describe)	Not supported — returns a Postgres ErrorResponse. Clients must use simple-query mode.
SSL/TLS	Declined at the wire level (N response). Use an external TLS terminator or connect with TLS disabled.
COPY protocol	Not supported.
Session variables via SET	SET statements are acknowledged without effect. Variables are not stored or forwarded.
extra in SessionContext	Always empty. Startup parameters beyond user, database, and query_tags are not forwarded to routers or adapters.

Related

• Frontends overview — shared dispatch and session model
• Routing and clusters — protocolBased router with postgresWire