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83c509a613
In left joins, even if the join condition is not matched, the system must emit a row for every row of the outer table: -- this must return t1.count() rows, with NULLs for all columns of t2 SELECT * FROM t1 LEFT JOIN t2 ON FALSE; Our logic for clearing the null flag was to do it in Next/Prev. However, this is problematic for a few reasons: - If the inner table of the left join is using SeekRowid, then Next/Prev is never called on its cursor, so the null flag doesn't get cleared. - If the inner table of the left join is using a non-covering index seek, i.e. it iterates its rows using an index, but seeks to the main table to fetch data, then Next/Prev is never called on the main table, and the main table's null flag doesn't get cleared. What this results in is NULL values incorrectly being emitted for the inner table after the first correct NULL row, since the null flag is correctly set to true, but never cleared. This PR fixes the issue by clearing the null flag whenever seek() is invoked on the cursor. Hence, the null flag is now cleared on: - next() - prev() - seek()