[pengpengyi92]

Fixes #942.

search_sql iterates columns twice, for the CTE and outer SELECT projections. A generator is exhausted after the first pass, producing an empty outer SELECT list. Materialize the iterable once before the existing projection logic; None, lists and tuples keep their behavior, and empty iterators now follow the existing empty-list default.

The new tests execute real FTS4/FTS5 queries through both search_sql and search. They cover empty/single/multiple column selections, list/tuple/iterator/generator inputs, output column order, filtering/pagination, rank inclusion, escaped column names and the original alias collision case.

Validation on Python 3.12.13 / SQLite 3.53.1:

• Before the source change: 28 new cases fail, 26 controls pass.
• After the change: all 54 new cases pass; 158 tests pass across the new module, test_fts.py and test_query.py, in both default and --sqlite-autocommit modes.
• Black and flake8 pass on both changed files; mypy passes on all 10 source files.

python -m pytest -q tests/test_fts_search_iterables.py tests/test_fts.py tests/test_query.py
python -m pytest -q tests/test_fts_search_iterables.py tests/test_fts.py tests/test_query.py --sqlite-autocommit

Only the search projection is changed, not index creation, query matching, SQL escaping or transaction handling. A consumed generator is not made reusable across separate calls. The complete optional-extension/OS matrix was not run.

AI assistance: prepared and checked with OpenAI Codex; no independent human review or hosted CI success is claimed.

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📚 Documentation preview 📚: https://sqlite-utils--943.org.readthedocs.build/en/943/