Results of LUA UDF that returns math.random() are not deterministic with same seed

Detail name	Value
Changelog Number	10535
Type	Bug
Status	Resolved
Affected Versions	Exasol 6.1.0, Exasol 6.2.0, Exasol 7.0.0
Fix Versions	Exasol 7.1.0
Resolution Date	2021-08-03

Description

A LUA UDF that initializes the random number generator with the same seed returns different results when called multiple times (>10000 times):

CREATE LUA SCALAR SCRIPT "RANDOMSEED" ("seed" DOUBLE) RETURNS DOUBLE AS
function run(ctx)
		math.randomseed(ctx.seed)
		return math.random()
	end
/
select distinct randomseed(123) from t_10000_rows;
--> returns multiple rows instead of one row

Workaround

Since this is limited to LUA UDFs, you can use a Python UDF instead of a Lua UDF:

CREATE PYTHON SCALAR SCRIPT "RANDOMSEED" ("seed" DOUBLE) RETURNS DOUBLE AS
import random
def run(ctx):
	random.seed(ctx.seed)
	return random.random()
/

Fix

The Lua UDF will only return one row, as expected.