System information functions

RisingWave provides functions to help you get system information, including databse, schema, user, role, session, and more.

current_database()

Returns the name of the current database. You can use this function in SQL commands, functions, and operators.

Syntax

current_database() → *current_database_name*

Examples

SELECT current_database(); →  `db_name`
SELECT count(current_database()); → 1

current_role

Returns the name of the role that the current user is acting as, if the current user is a member of one or more roles.

Syntax

current_role → *current_role_name* 
current_role() → *current_role_name*

Example

SELECT current_role(); → 'root'

current_shema

Returns the current schema. This is the schema that will be used for creating tables or other named objects without specifying a target schema.

Syntax

current_schema → *current_schema_name* 
current_schema() → *current_schema_name*

Example

SELECT current_schema(); → 'public'

current_user

Returns the name of the current effective user.

Syntax

current_user → *user_name*
current_user() → *user_name* 

Example

SELECT current_user(); → `root`

pg_get_viewdef()

Returns the definition of a specified view or materialized view.

Syntax

pg_get_viewdef(view_name) → text

Examples

-- Create a table
CREATE TABLE table1 (
    id int PRIMARY KEY,
    name VARCHAR 
);

-- Create a materialized view
CREATE MATERIALIZED VIEW materialized_view1 AS 
SELECT id, name 
FROM table1;

-- Retrieve the definition of the materialized view using pg_get_viewdef
SELECT pg_get_viewdef('materialized_view1'::regclass);
----RESULT
 SELECT id, name FROM table1
(1 row)

pg_typeof()

Returns the standard name of the data type of the provided value. More specifically, it returns the OID of the data type of the provided value. It returns a regtype, which is an OID alias type. Therefore it’s the same as an OID for comparison purposes but displays as a type name.

Syntax

pg_typeof() → regtype

Examples

SELECT pg_typeof(round(null));  → `double precision`
SELECT pg_typeof(row(true, 1, 'hello')); → `record`
SELECT pg_typeof(array[1, 2]); → `integer[]`

pg_relation_size

Computes the disk space used by one “fork” of the specified relation.

Syntax

pg_relation_size ( relation regclass [, 'main' ] ) → bigint

Returns the size of the main data fork of the relation. This function can be used to determine if the main data fork of a relation exists. If its size is not 0, it means that the main data fork of the relation exists.

Examples

SELECT pg_relation_size('t') != 0; → t
SELECT pg_relation_size('t', 'main') != 0; → t

session_user

Returns the name of the current session user.

Syntax

session_user → *session_user_name*
session_user() → *session_user_name* 

Example

SELECT session_user(); → `root`

user

Returns the name of the current database user.

Syntax

user → *user_name*
user() → *user_name* 

Example

SELECT user(); → `root`

version()

Displays the PostgreSQL version and the RisingWave version implemented in the current instance of RisingWave.

Example

SELECT version ();
---------RESULT
 version 
-----------------
 PostgreSQL 8.3-RisingWave-1.0.0-alpha (76672d87cf5c20aa8fbb6f11996ef15255443b51)
(1 row)