Add Python language functions

[electrum]

Description

This adds support for functions using the Python language. Example:

WITH FUNCTION xor(a boolean, b boolean)
RETURNS boolean
LANGUAGE PYTHON
WITH (handler = 'bool_xor')
AS $$
import operator
def bool_xor(a, b):
    return operator.xor(a, b)
$$
SELECT xor(true, false), xor(false, true)

The handler property specifies the Python function to execute when the Trino function is called.

See TestPythonFunctions for more examples.

Implementation

Python functions are executed in the same JVM as Trino using Chicory, a native JVM WebAssembly runtime, which is secure and fully sandboxed. The Python environment is limited to 32MB of memory (with the engine creating separate environments for each concurrent function invocation). As with other functions, there is no time or CPU limit, but execution is interruptible, and thus will be aborted if the query is cancelled.

Data Types

The following table shows supported Trino types and their corresponding Python types:

Trino Type	Python Type
row	tuple
array	list
map	dict
boolean	bool
tinyint	int
smallint	int
integer	int
bigint	int
real	float
double	float
decimal	decimal.Decimal
varchar	str
varbinary	bytes
date	datetime.date
time	datetime.time
time with time zone	datetime.time with datetime.tzinfo
timestamp	datetime.datetime
timestamp with time zone	datetime.datetime with datetime.tzinfo 1
interval year to month	int as the number of months
interval day to second	datetime.timedelta
json	str
uuid	uuid.UUID
ipaddress	ipaddress.IPv4Address or ipaddress.IPv6Address

Python datetime objects only support microsecond precision. Trino argument values with greater precision will be rounded when converted to Python values, and Python return values will be rounded if the Trino return type has less than microsecond precision.

Dependencies

Python WASM integration: trinodb/trino-wasm-python#1

Support for language functions: #24105

Release notes

(x) Release notes are required. Please propose a release note for me.

Footnotes

1. Currently, only fixed offset time zones are supported. Timestamps with political time zones will have the zone converted to the zone's offset for the timestamp's instant. ↩

[dain]

minor comments, but looks good