Query: Insert Select 1 ordering for rownumber paging when there is no…

[smitpatel]

… other ordering

Case when there is no explicit order by and no implicit key ordering for keyless entities

Resolves #18925

[roji]

The ORDER BY clause is optional in both PostgreSQL and Sqlite:

DROP TABLE empsalary;
CREATE TABLE empsalary (depname TEXT, salary DOUBLE PRECISION);
INSERT INTO empsalary (depname, salary) VALUES ('Sales', '10'), ('Sales', '20'), ('Engineering', '10');
SELECT depname, ROW_NUMBER() OVER(PARTITION BY depname) FROM empsalary;

In general, I'm still not sure what the story is for provider-specific stuff in SelectExpression... Assuming it's OK for providers to extend SelectExpression, maybe just expose a flag for injecting SELECT 1 (both here and in Skip/Take)?

[smitpatel]

It is likely that SelectExpression may not remain extensible.

[smitpatel]

@roji Filed #19331 to refactor it so that providers can influence.