I was experimenting with ways to return only the last row of a recursive CTE,
when I came across some curious behaviour.
The following two examples were run from the shell of 3.8.7.2:
1)
PRAGMA reverse_unordered_selects = OFF;
WITH RECURSIVE
i(i) AS (SELECT 1 UNION ALL SELECT i+1 FROM i LIMIT 5)
SELECT * FROM i;
1
2
3
4
5
2)
PRAGMA reverse_unordered_selects = ON;
WITH RECURSIVE
i(i) AS (SELECT 1 UNION ALL SELECT i+1 FROM i LIMIT 5)
SELECT * FROM i;
1
2
3
4
5
The documentation for PRAGMA reverse_unordered_selects states that "SQLite
makes no guarantees about the order of results if a SELECT omits the ORDER
BY clause. Even so, the order of results does not change from one run to the
next...", so one would expect example 2 to output the results in the reverse
order of example 1. I could not find anything in the documentation that
suggests these results are expected.
If this is not a bug, then this behaviour should be mentioned on either the
Pragma, or WITH Clause documentation pages.
~Jaak
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