rubenada commented on code in PR #5370:
URL: https://github.com/apache/calcite/pull/5370#discussion_r4528227558
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site/_docs/reference.md:
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@@ -562,6 +563,56 @@ MATCH_CONDITION left_table.timecol <= right_table.timecol
ON left_table.col = right_table.col
```
+### Search ordering in recursive queries
+
+`SEARCH` generates a column that can be used to order the output of a recursive
+query. `SEARCH DEPTH FIRST` orders a node before its descendants and those
+descendants before the next sibling. `SEARCH BREADTH FIRST` orders by depth,
+then by the specified columns within each level. The columns in `BY` are
+compared in their listed order, with null values sorting last.
+
+For example:
+
+{% highlight sql %}
+WITH RECURSIVE
+ edges(src, dst) AS (VALUES (0, 2), (0, 1), (1, 4), (2, 3)),
+ walk(node) AS (
+ VALUES (0)
+ UNION ALL
+ SELECT e.dst FROM walk AS w JOIN edges AS e ON e.src = w.node
+ ) SEARCH DEPTH FIRST BY node SET search_order
+SELECT node FROM walk ORDER BY search_order;
+{% endhighlight %}
+
+This returns `0, 1, 4, 2, 3`. Changing `DEPTH` to `BREADTH` returns
+`0, 1, 2, 3, 4`. `SEARCH` does not itself sort the result or control the
+physical evaluation order; use an explicit `ORDER BY` on the generated column.
+Rows with equal search keys have no guaranteed relative order.
+
+The depth-first column is an array of key rows representing the path. The
+breadth-first column is a row containing the depth (starting at zero) and the
Review Comment:
Would it be interesting to "document" the $DEPTH field, in case users want
to read it? Or shall we keep it as an implementation detail?
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