Summary of Built-in Functions

Apache Cloudberry supports built-in functions and operators including analytic functions and window functions that can be used in window expressions.

📄️ JSON Functions and Operators

This document describes:

📄️ Window Functions

The following are Apache Cloudberry built-in window functions. All window functions are immutable.

📄️ Advanced Aggregate Functions

The following built-in advanced analytic functions are Cloudberry extensions of the PostgreSQL database. Analytic functions are immutable.

📄️ Text Search Functions and Operators

The following tables summarize the functions and operators that are provided for full text searching.

📄️ Range Functions and Operators

The following table shows the operators available for range types.

Apache Cloudberry function types

Apache Cloudberry evaluates functions and operators used in SQL expressions. Some functions and operators are only allowed to run on the coordinator since they could lead to inconsistencies in Apache Cloudberry segment instances. This table describes the Apache Cloudberry Function Types.

Function Type	Cloudberry Support	Description	Comments
IMMUTABLE	Yes	Relies only on information directly in its argument list. Given the same argument values, always returns the same result.
STABLE	Yes, in most cases	Within a single table scan, returns the same result for same argument values, but results change across SQL statements.	Results depend on database lookups or parameter values. current_timestamp family of functions is STABLE; values do not change within an execution.
VOLATILE	Restricted	Function values can change within a single table scan. For example: random(), timeofday().	Any function with side effects is volatile, even if its result is predictable. For example: setval().

In Apache Cloudberry, data is divided up across segments — each segment is a distinct PostgreSQL database. To prevent inconsistent or unexpected results, do not run functions classified as VOLATILE at the segment level if they contain SQL commands or modify the database in any way. For example, functions such as setval() are not allowed to run on distributed data in Apache Cloudberry because they can cause inconsistent data between segment instances.

To ensure data consistency, you can safely use VOLATILE and STABLE functions in statements that are evaluated on and run from the coordinator. For example, the following statements run on the coordinator (statements without a FROM clause):

SELECT setval('myseq', 201);
SELECT foo();

If a statement has a FROM clause containing a distributed table and the function in the FROM clause returns a set of rows, the statement can run on the segments:

SELECT * from foo();

Apache Cloudberry does not support functions that return a table reference (rangeFuncs) or functions that use the refCursor datatype.

Built-in functions and operators

The following table lists the categories of built-in functions and operators supported by PostgreSQL. All functions and operators are supported in Apache Cloudberry as in PostgreSQL with the exception of STABLE and VOLATILE functions, which are subject to the restrictions noted in Apache Cloudberry Function Types. See the Functions and Operators section of the PostgreSQL documentation for more information about these built-in functions and operators.

Operator/Function Category	VOLATILE Functions	STABLE Functions	Restrictions
Logical Operators
Comparison Operators
Mathematical Functions and Operators	random setseed
String Functions and Operators	All built-in conversion functions	convert pg_client_encoding
Binary String Functions and Operators
Bit String Functions and Operators
Pattern Matching
Data Type Formatting Functions		to_char to_timestamp
Date/Time Functions and Operators	timeofday	age current_date current_time current_timestamp localtime localtimestamp now
Enum Support Functions
Geometric Functions and Operators
Network Address Functions and Operators
Sequence Manipulation Functions	nextval() setval()
Conditional Expressions
Array Functions and Operators		All array functions
Aggregate Functions
Subquery Expressions
Row and Array Comparisons
Set Returning Functions	generate_series
System Information Functions		All session information functions All access privilege inquiry functions All schema visibility inquiry functions All system catalog information functions All comment information functions All transaction ids and snapshots
System Administration Functions	set_config pg_cancel_backend pg_reload_conf pg_rotate_logfile pg_start_backup pg_stop_backup pg_size_pretty pg_ls_dir pg_read_file pg_stat_file	current_setting All database object size functions	> Note The function pg_column_size displays bytes required to store the value, possibly with TOAST compression.
XML Functions and function-like expressions		cursor_to_xml(cursor refcursor, count int, nulls boolean, tableforest boolean, targetns text) cursor_to_xmlschema(cursor refcursor, nulls boolean, tableforest boolean, targetns text) database_to_xml(nulls boolean, tableforest boolean, targetns text) database_to_xmlschema(nulls boolean, tableforest boolean, targetns text) database_to_xml_and_xmlschema(nulls boolean, tableforest boolean, targetns text) query_to_xml(query text, nulls boolean, tableforest boolean, targetns text) query_to_xmlschema(query text, nulls boolean, tableforest boolean, targetns text) query_to_xml_and_xmlschema(query text, nulls boolean, tableforest boolean, targetns text) schema_to_xml(schema name, nulls boolean, tableforest boolean, targetns text) schema_to_xmlschema(schema name, nulls boolean, tableforest boolean, targetns text) schema_to_xml_and_xmlschema(schema name, nulls boolean, tableforest boolean, targetns text) table_to_xml(tbl regclass, nulls boolean, tableforest boolean, targetns text) table_to_xmlschema(tbl regclass, nulls boolean, tableforest boolean, targetns text) table_to_xml_and_xmlschema(tbl regclass, nulls boolean, tableforest boolean, targetns text) xmlagg(xml) xmlconcat(xml[, ...]) xmlelement(name name [, xmlattributes(value [AS attname] [, ... ])] [, content, ...]) xmlexists(text, xml) xmlforest(content [AS name] [, ...]) xml_is_well_formed(text) xml_is_well_formed_document(text) xml_is_well_formed_content(text) xmlparse ( { DOCUMENT | CONTENT } value) xpath(text, xml) xpath(text, xml, text[]) xpath_exists(text, xml) xpath_exists(text, xml, text[]) xmlpi(name target [, content]) xmlroot(xml, version text | no value [, standalone yes|no|no value]) xmlserialize ( { DOCUMENT | CONTENT } value AS type ) xml(text) text(xml) xmlcomment(xml) xmlconcat2(xml, xml)