Postgres compatibility

The engine parses DuckDB SQL and adds the Postgres forms drivers and ORMs actually send: $1 parameters, public. qualifiers, SERIAL, FOR UPDATE, GROUP BY on a key, col = ANY($1), ON CONFLICT, ON DUPLICATE KEY UPDATE, and the connect-time catalog probes of psycopg, SQLAlchemy, Django, Prisma and GORM. Where DuckDB and Postgres disagree on a result, the engine follows Postgres for the cases that matter to application code: decimal arithmetic is exact and rounds like Postgres, INTEGER is 64-bit, VARCHAR(n) is enforced.

The status vocabulary

Every row on the sub-pages uses one of these:

Badge	Meaning
Enforced23505	The engine guarantees it. The code is the SQLSTATE a violation raises.
Supported	The statement or function works as in Postgres.
Partial	Works, with a documented difference described in the row.
Accepted · NOTICE	Accepted so migrations and drivers run, but not acted on. A `NOTICE` tells you each time.
Accepted · no effect	Accepted for driver compatibility with no effect and no notice.
Refused0A000	Rejected with the SQLSTATE shown (omitted where it varies). The message names what to use instead.
Planned	Not available; on the roadmap.

A behaviour younger than 0.1.40 carries its release, for example since 0.1.43. Your deployment’s version is in SHOW server_version under the dodil suffix, or from dodil data health.

Pages

Page	Question it answers
Data types	Which Postgres types can I declare, what is exact, what does my driver see on the wire?
Statements	Which DDL, DML, transaction and session statements work, and which are refused?
Constraints	Which constraints are enforced, which are accepted with a notice, which are refused?
Functions & operators	Which functions exist, how does arithmetic round, how do JSON and vector operators work?
Catalog	What does `information_schema` and `pg_catalog` report; what does `DESCRIBE` show?

Concurrency, isolation and FOR UPDATE are on Transactions & concurrency. The single list of everything that differs from Postgres is Limits & differences.