Postgres compatibility

Egres speaks the PostgreSQL wire protocol and parses SQL with Postgres’s own grammar (libpg_query), so every statement Postgres accepts parses. This page is a checklist of what executes in the current release. “Not yet” means exactly that: the list grows with each release.

About this page

This page is generated and maintained with AI, read from the Egres source at each release rather than written by hand. If something here does not match what the server does, open an issue.

What a “not yet” looks like to a client

A statement Egres recognises but does not run yet returns a Postgres error with SQLSTATE 0A000 (feature not supported) and a one-line reason, such as only count(*) is supported in SELECT. A statement kind it does not recognise returns unsupported statement, also 0A000. Syntax errors return 42601.

Protocol and clients

Feature	Status	Notes
Simple query protocol	Yes	One statement per message. A message with several statements separated by ; runs the first one only.
Extended query protocol (Parse, Bind, Describe, Execute, Close, Sync, Flush)	Yes	Each session caches its parsed statements by SQL text.
$1-style parameters	Yes	In WHERE, SET and VALUES, up to $65535.
Parameters in text format	Yes	Any column type.
Parameters in binary format	Partial	bool, int2, int4, int8, float4, float8.
Parameter type inference at Parse	Not yet	The server echoes the OIDs the client sent.
Result columns in text format	Yes
Result columns in binary format	Not yet
Portal row limits (Execute with a row count)	Not yet
Empty query	Yes	EmptyQueryResponse, as in Postgres.
TLS	Not yet	SSLRequest is answered with N; clients with sslmode=prefer or disable continue over plain TCP.
Authentication	Not yet	Every connection is accepted.
CancelRequest	Not yet	The request is accepted and ignored.
pg_catalog, information_schema	Not yet	psql’s backslash commands (\d, \dt, \l) depend on them.
COPY	Not yet
LISTEN / NOTIFY	Not yet
Cursors, PREPARE as a statement	Not yet
NoticeResponse	Not yet

The default SQL port is 3210. The database egres exists from the first boot, and a session that names no database lands in it. psql reports the server version as 13.0, the protocol version Egres speaks. The clients used in the quickstart and the benchmarks are psql and pgbench.

Statements

Statement	Status	Notes
CREATE DATABASE name	Yes	TEMPLATE source branches the source database. OWNER, ENCODING and the other options are accepted and ignored.
DROP DATABASE name	Yes	Except the default database egres.
CREATE TABLE [IF NOT EXISTS]	Partial	See Tables.
CREATE TABLE dst AS TABLE src	Yes	Branches src with its indexes. WITH NO DATA gives the definition and indexes, empty. AS SELECT * FROM src is the same statement.
CREATE TABLE dst AS SELECT ... with a WHERE, column list or other clause	Not yet
DROP TABLE [IF EXISTS] name	Yes	One table per statement.
CREATE [UNIQUE] INDEX [IF NOT EXISTS]	Partial	See Indexes.
DROP INDEX [IF EXISTS] name	Yes	One index per statement. CONCURRENTLY is not needed: every index change is online.
ALTER TABLE, ALTER INDEX, ALTER DATABASE	Not yet
TRUNCATE	Not yet
INSERT ... VALUES	Yes	Multi-row VALUES and an explicit column list.
INSERT ... SELECT, DEFAULT VALUES, DEFAULT as a value, ON CONFLICT, RETURNING	Not yet
SELECT	Partial	See Queries.
UPDATE ... SET ... [WHERE]	Yes	SET takes a literal, a parameter, a column, or + - * / % || over them.
UPDATE ... FROM, RETURNING, WITH	Not yet
DELETE FROM t [WHERE]	Yes	Without WHERE it deletes every row.
DELETE ... USING, RETURNING, WITH	Not yet
BEGIN, START TRANSACTION, COMMIT, END, ROLLBACK	Yes	Transaction modes such as ISOLATION LEVEL are accepted and ignored; isolation is snapshot isolation.
SAVEPOINT, PREPARE TRANSACTION	Not yet
DDL inside a transaction block	Not yet	Returns 25001. Each DDL statement runs as its own transaction.
SET, RESET	Yes	Any parameter, accepted and ignored.
SHOW	Not yet
EXPLAIN, ANALYZE	Not yet
VACUUM	Not applicable	See No VACUUM.
CREATE FUNCTION, CREATE PROCEDURE, DO (user-defined functions and procedures)	Not yet
CREATE TRIGGER	Not yet
CREATE VIEW, CREATE MATERIALIZED VIEW	Not yet
CREATE SEQUENCE, nextval()	Not yet
CREATE SCHEMA, CREATE EXTENSION	Not yet
GRANT, REVOKE, CREATE ROLE	Not yet

Queries

The shape a SELECT takes today:

SELECT column, ... | * | count(*)
FROM one_table
[WHERE predicate]
[FOR UPDATE]
[LIMIT n]

Clause	Status	Notes
SELECT 1, constants with no FROM	Yes	One row; a pool’s connection check. Aliases allowed.
Column references and * in the target list	Yes	The egid column can be selected by name.
count(*)	Yes	Alone in the target list.
Other aggregates, expressions, casts, aliases, functions in the target list	Not yet
One table in FROM, named directly	Yes
JOIN, subqueries, VALUES in FROM, table aliases	Not yet
WHERE	Partial	See below.
FOR UPDATE	Yes	Locks every matching row for the rest of the transaction. Not with count(*).
FOR SHARE, NOWAIT, SKIP LOCKED, FOR UPDATE OF	Not yet
LIMIT n with an integer literal, LIMIT ALL	Yes
LIMIT with a parameter or expression, OFFSET, FETCH ... WITH TIES	Not yet
ORDER BY, GROUP BY, DISTINCT, HAVING	Not yet

Rows come back in egid order, which is insertion order, whether a scan or an index produced them.

WHERE

Form	Status	Notes
column = literal	Yes	A number, a string, a boolean or NULL. column = NULL matches nothing, as in Postgres. A literal that does not parse as the column’s type returns 22P02.
column = $n	Yes
column IS NULL, column IS NOT NULL	Yes
AND, OR, NOT	Yes	Nested to any depth.
egid = N	Yes	A single-hop point read; N is a positive integer. See Extensions.
<, <=, >, >=, <>	Not yet
BETWEEN, LIKE, ILIKE, IN (...), IS DISTINCT FROM	Not yet
A function or expression on either side, a bare boolean column, a column compared with a column	Not yet

Any indexed column in the predicate drives the query through its bitmap index, and AND, OR and NOT over indexed columns become bitmap operations. A predicate on an unindexed column scans the table with the predicate applied to each row. A mixed predicate uses the indexed terms to pick a superset of the rows and re-checks the whole predicate on each. An index still being built is used once its backfill completes.

Tables

CREATE TABLE [IF NOT EXISTS] name (
  column type [PRIMARY KEY | UNIQUE],
  ...
);

Feature	Status	Notes
PRIMARY KEY on one column	Yes	One per table.
UNIQUE on one column	Yes	NULL is allowed, and two NULLs do not collide, as in Postgres.
NOT NULL, DEFAULT, CHECK, REFERENCES, GENERATED	Not yet
Table-level constraints: PRIMARY KEY (a, b), UNIQUE (a, b), FOREIGN KEY	Not yet
char(n), varchar(n) length modifiers	Yes	Up to 10,485,760, as in Postgres. A bare char is char(1); a bare varchar is text.
Length modifiers on other types	Not yet
A table with no PRIMARY KEY	Yes	Keyed by egid.

NULL in the primary key column returns 23502. egid is a reserved column name. Table and index definitions live in reserved tables inside the database, so they branch with it.

Indexes

CREATE [UNIQUE] INDEX [IF NOT EXISTS] name ON table (column);

Feature	Status	Notes
Single-column index	Yes	One index per column, counting the index behind a PRIMARY KEY or UNIQUE column.
UNIQUE index	Yes
USING btree	Yes	Accepted; every Egres index is a bitmap index. See Indexes.
Online creation	Yes	The index is backfilled while writes continue and becomes visible when the backfill completes, so CONCURRENTLY is not needed.
Composite, expression and partial indexes	Not yet
INCLUDE, DESC, NULLS FIRST, TABLESPACE	Not yet
Other access methods (hash, gin, gist, brin)	Not yet
Indexes on interval columns	Not yet	As a primary key, a unique column or by CREATE INDEX.
Dropping the primary key’s index	Not yet

Data types

Postgres type	Status	Notes
boolean	Yes	Literals t, true, 1, yes, on and their opposites.
smallint, integer, bigint	Yes
real, double precision	Yes
text, varchar, varchar(n), char(n)	Yes	Values are valid UTF-8 (22021 otherwise); a value longer than n returns 22001.
bytea	Yes
date, timestamp, timestamptz	Yes
time, interval, uuid	Partial	The column can be declared and holds NULL. Writing a value into it or comparing against it: not yet (0A000).
time with time zone	Not yet
numeric, decimal	Not yet
serial, bigserial	Not yet	egid gives an insertion-ordered id today.
json, jsonb	Not yet
Arrays, enum, composite, range, money, inet, bit, tsvector, geometric types	Not yet

Assignments in SET follow Postgres: any integer into any numeric column with a range check (22003 on overflow), floats into floats, strings into strings. A float into an integer column returns 42804. Division by zero returns 22012.

Functions and operators

Feature	Status	Notes
count(*)	Yes	Alone in the target list.
CURRENT_TIMESTAMP, LOCALTIMESTAMP	Partial	In INSERT ... VALUES, into a timestamp or timestamptz column; the transaction’s start time, as in Postgres. In WHERE or SET: not yet.
+, -, *, /, % on numeric types, unary minus	Yes	In UPDATE ... SET, over literals, parameters and columns of the same row.
|| on strings	Yes	In UPDATE ... SET.
now(), casts, string and date functions, COALESCE, CASE, every other function and operator	Not yet
User-defined functions, in SQL or any other language	Not yet

Extensions

Things Egres accepts that Postgres does not.

• egid. Every row has a 64-bit id, assigned at insert and increasing within the table. SELECT egid, ... reads it and WHERE egid = N is a single-hop point read. It is assigned by the server, so an explicit value in INSERT or UPDATE is not accepted. It rides the wire as numeric.
• Unsigned integers. uint2, uint4 and uint8 are column types. Clients see uint2 as int4, uint4 as int8 and uint8 as numeric.
• CREATE DATABASE new TEMPLATE src branches a database instantly instead of copying its files, and CREATE TABLE dst AS TABLE src branches a table with its indexes instead of copying rows without them. See Branching.

Behaviour today

• Isolation is snapshot isolation. Reads never block. A statement that locks a row committed after its snapshot re-runs itself at the newer snapshot; in a multi-statement transaction that may instead fail with 40001, the same serialization failure Postgres returns. See Transactions.
• Deadlocks are detected at lock time. The lock request that would close a cycle fails immediately with 40P01, and that transaction’s locks are released. There is no deadlock_timeout and no lock_timeout.
• Writes run on the Raft leader. This release runs a single node, which is always the leader. Multi-node clusters come in a later release.
• A failed statement fails the transaction, as in Postgres: only COMMIT and ROLLBACK are accepted until the block ends (25P02 otherwise), and both roll back.
• A read below the retention floor returns 72000, snapshot too old. See Garbage collection.