Ref T13091. The Ferret "rank" column is a function of the query text and looks something like SELECT ..., 2 + 2 AS rank, ....

You can't apply conditions to this kind of dynamic column with a WHERE clause: you get a slightly unhelpful error like "column rank unknown in where clause". You must use HAVING:

mysql> SELECT 2 + 2 AS x WHERE x = 4;
ERROR 1054 (42S22): Unknown column 'x' in 'where clause'
mysql> SELECT 2 + 2 AS x HAVING x = 4;
+---+
| x |
+---+
| 4 |
+---+
1 row in set (0.00 sec)

Add a flag to paging column definitions to let them specify that they must be applied with HAVING, then apply the whole paging clause with HAVING if any column requires HAVING.

• In Maniphest, ran a fulltext search matching more than 100 results, ordered by "Relevance", then clicked "Next Page".
• Before patch: query with ... WHERE rank > 123 OR ... caused MySQL error because rank is not a WHERE-able column.
• After patch: query builds as ... HAVING rank > 123 OR ..., pages properly, no MySQL error.