Postgres wire

ClickHouse implements the PostgreSQL wire protocol so psql, libpq, and tools that speak Postgres can connect without changes. Default port: 9005. Implementation: src/Server/PostgreSQLHandler.cpp and src/Server/PostgreSQLHandlerFactory.cpp, with the parser-side support under src/Core/PostgreSQL*.cpp and src/Parsers/PostgreSQL/.

psql "host=localhost port=9005 user=user dbname=default sslmode=disable"

What works

• Simple query and extended query protocols.
• Prepared statements.
• Authentication: md5, scram-sha-256, cleartext.
• TLS.
• Cursor-style streaming (basic) and chunked rows.
• ClickHouse SQL dialect (with light translation of INFORMATION_SCHEMA queries).

What doesn't

• Postgres-specific built-ins (pg_catalog functions beyond a small compatibility shim).
• Server-side commands (COPY, LISTEN/NOTIFY, PREPARE TRANSACTION).
• Stored procedures, triggers.

Type mapping

ClickHouse types are advertised with the closest matching PostgreSQL OID:

• Numeric types map to int4/int8/numeric/float8.
• String → text.
• DateTime, Date → timestamp, date.
• Array(T) → text[] (or matched array OIDs where possible).
• UUID → uuid.
• Decimal(P,S) → numeric(P,S).

When to use it

• You already have a Postgres-only client or BI tool.
• You want to combine ClickHouse with the ecosystem of psql, pgcli, and Postgres-flavoured ORMs.
• You're migrating an internal tool from Postgres to ClickHouse and want a transitional layer.

Postgres-as-a-source

The opposite direction (read from / write to Postgres) is supported via:

• The PostgreSQL table engine and postgresql(...) table function.
• MaterializedPostgreSQL engine for replicating an upstream Postgres database into a local schema. Backed by logical replication slots; see src/Storages/PostgreSQL/ and src/Databases/MaterializedPostgreSQL/.
• Dictionaries with <source><postgresql> (see Dictionaries).

Related pages

• Server protocols
• MySQL wire
• Other engines