PostgreSQL Wire Protocol

Overview of QuestDB’s PostgreSQL wire protocol compatibility and features

QuestDB implements the PostgreSQL wire protocol, allowing you to query data using PostgreSQL-compatible tools and drivers. This enables seamless integration with a wide ecosystem of PostgreSQL clients and applications.

Protocol compatibility

QuestDB supports PostgreSQL wire protocol connections on port 8812 by default. The implementation is compatible with PostgreSQL 11.3 wire protocol specification.

Supported features

• Simple Query protocol: Execute queries directly using the simple query flow
• Extended Query protocol: Prepare statements with parameter binding for better performance
• Named statements and portals: Create and reuse prepared statements across multiple executions
• Binary and text format: Support for both text and binary parameter/result encoding
• Authentication: Username and password authentication with configurable users
• TLS/SSL encryption: Secure connections using TLS
• Transaction support: BEGIN, COMMIT, and ROLLBACK statements
• Query caching: Automatic caching of SELECT and INSERT queries for improved performance

Server version

QuestDB reports itself as PostgreSQL version 11.3 to maintain compatibility with client drivers that perform version checks.

Default configuration

Parameter	Default Value	Description
Port	8812	PostgreSQL wire protocol listening port
Bind address	0.0.0.0:8812	Network interface and port
Username	admin	Default admin username
Password	quest	Default admin password
Read-only user	user	Optional read-only username
Read-only password	quest	Optional read-only password
Connection limit	64	Maximum concurrent connections
Connection timeout	300000ms	Idle connection timeout
Receive buffer	1MB	Socket receive buffer size
Send buffer	1MB	Socket send buffer size

Authentication

QuestDB supports two user types for PostgreSQL wire protocol:

1. Admin user (default: admin/quest): Full read and write access
2. Read-only user (default: user/quest): Query-only access, data mutation queries are rejected

The read-only user must be explicitly enabled in the server configuration:

server.conf

pg.readonly.user.enabled=true

Query caching

QuestDB implements intelligent query caching for PostgreSQL protocol queries:

• SELECT cache: Enabled by default, caches compiled query plans for SELECT statements
• INSERT cache: Enabled by default, caches compiled INSERT statements per session

Cache configuration:

server.conf

# SELECT query cache
pg.select.cache.enabled=true
pg.select.cache.block.count=16  # 8 * worker_count
pg.select.cache.row.count=4     # 2 * worker_count

# INSERT query cache
pg.insert.cache.enabled=true
pg.insert.cache.block.count=4
pg.insert.cache.row.count=4

Configuration options

Enable or disable the PostgreSQL wire protocol in server.conf:

server.conf

# Enable PostgreSQL wire protocol
pg.enabled=true

# Bind to specific interface and port
pg.net.bind.to=0.0.0.0:8812

# Authentication
pg.user=admin
pg.password=quest

# Connection limits
pg.net.connection.limit=64
pg.net.connection.timeout=300000

# Buffer sizes
pg.recv.buffer.size=1M
pg.send.buffer.size=1M

# Worker threads
pg.worker.count=2

# Prepared statement limits
pg.named.statement.limit=10000

# Pipeline capacity for batch operations
pg.pipeline.capacity=64

Limitations

While QuestDB implements the PostgreSQL wire protocol, it is not a full PostgreSQL database. Some limitations include:

• SQL dialect differences: QuestDB uses its own SQL dialect optimized for time-series data
• System tables: PostgreSQL system catalogs are partially implemented for compatibility
• BLOB size limit: Maximum BLOB size on query is 512KB by default (configurable via pg.max.blob.size.on.query)
• Unsupported statements: Some PostgreSQL-specific statements are not supported
• DELETE statement: QuestDB does not support DELETE; use ALTER TABLE DROP PARTITION instead

Performance considerations

• Use prepared statements with parameter binding for repeated queries
• Enable query caching (enabled by default) for better performance
• Increase pg.pipeline.capacity if using large batch inserts (>64 rows)
• Configure pg.worker.count based on available CPU cores
• Use binary format for parameters when possible to reduce serialization overhead

Next steps

Connection

Learn how to connect using various PostgreSQL drivers

Queries

Execute queries via the PostgreSQL protocol

Related documentation

• Configuration
• SQL Overview
• InfluxDB Line Protocol
• REST API