In general each database has different rules for handling non-deterministic expressions. We are similar to H2, but it looks like you are expecting Postgres style handling such that uncorrelated subqueries are always treated as deterministic.

UPDATE command with non-pushdown functions leads to TEIID30253 error -------------------------------------------------------------------- Key: TEIID-4423 URL: https://issues.jboss.org/browse/TEIID-4423 Project: Teiid Issue Type: Bug Components: Query Engine Affects Versions: 8.12.x Environment: teiid-8.12-Beta1 on Red Hat JBoss Enterprise Application Platform - Version 6.3.0.GA teiid-9.0.3 on WildFly Full 9.0.2.Final Reporter: dalex dalex Assignee: Steven Hawkins Running the following queries: {code:sql} update test.textagg_test_2 set id =(select uuid());; {code} or {code:sql} update test.textagg_test_2 set id =(select rand());; {code} leads to the following errors: {code} TEIID30253 Source UPDATE or DELETE command "UPDATE test.textagg_test_2 SET id = (SELECT uuid() LIMIT 2)" contains non-pushdown constructs and no compensating action can be taken as the table lacks a unique key or the source does not support equality predicates. {code} and {code} TEIID30253 Source UPDATE or DELETE command "UPDATE test.textagg_test_2 SET id = convert((SELECT rand() LIMIT 2), string)" contains non-pushdown constructs and no compensating action can be taken as the table lacks a unique key or the source does not support equality predicates. {code} though the following query: {code:sql} update test.textagg_test_2 set id =(select now());; {code} works without errors.