docs: missing documentation for enable_dst_hour_fix, enable_loser_tree_merge_sort, and enable_sort_spill_prefetch settings

[sundy-li]

Missing Feature Documentation

Three session settings are implemented in Databend source but are not documented.

Settings

enable_dst_hour_fix (default: 0)

• When enabled, time conversion handles invalid DST (Daylight Saving Time) transitions by adding an hour. Accuracy is not guaranteed.
• Useful for handling ambiguous timestamps during DST transitions.

enable_loser_tree_merge_sort (default: 1)

• Enables loser tree algorithm for multi-way merge sort. More efficient than naive merge for large numbers of sorted streams.

enable_sort_spill_prefetch (default: 1)

• Enables asynchronous prefetch when restoring spilled sort blocks, overlapping I/O with computation.

Source Reference

• src/query/settings/src/settings_default.rs

What's Missing

• None of these settings appear in any documentation page
• No mention of enable_dst_hour_fix in the datetime/timezone docs

Suggested Location

• Settings reference page
• Cross-reference enable_dst_hour_fix from the timezone/datetime docs