table.search_sql(include_rank=True) option (#480)

* search_sql add include_rank option
* add test
* add FTS4 test
* Apply Black

Thanks, @chapmanjacobd

Author: chapmanjacobd

sqlite_utils/db.py

@@ -2376,6 +2376,7 @@ def search_sql(
         limit: Optional[int] = None,
         offset: Optional[int] = None,
         where: Optional[str] = None,
+        include_rank: bool = False,
     ) -> str:
         """ "
         Return SQL string that can be used to execute searches against this table.
@@ -2385,6 +2386,7 @@ def search_sql(
         :param limit: SQL limit
         :param offset: SQL offset
         :param where: Extra SQL fragment for the WHERE clause
+        :param include_rank: Select the search rank column in the final query
         """
         # Pick names for table and rank column that don't clash
         original = "original_" if self.name == "original" else "original"
@@ -2427,6 +2429,8 @@ def search_sql(
             rank_implementation = "rank_bm25(matchinfo([{}], 'pcnalx'))".format(
                 fts_table
             )
+        if include_rank:
+            columns_with_prefix_sql += ",\n    " + rank_implementation + " rank"
         limit_offset = ""
         if limit is not None:
             limit_offset += " limit {}".format(limit)

tests/test_fts.py

@@ -556,6 +556,50 @@ def test_enable_fts_error_message_on_views():
                 "    rank_bm25(matchinfo([books_fts], 'pcnalx'))"
             ),
         ),
+        (
+            {"include_rank": True},
+            "FTS5",
+            (
+                "with original as (\n"
+                "    select\n"
+                "        rowid,\n"
+                "        *\n"
+                "    from [books]\n"
+                ")\n"
+                "select\n"
+                "    [original].*,\n"
+                "    [books_fts].rank rank\n"
+                "from\n"
+                "    [original]\n"
+                "    join [books_fts] on [original].rowid = [books_fts].rowid\n"
+                "where\n"
+                "    [books_fts] match :query\n"
+                "order by\n"
+                "    [books_fts].rank"
+            ),
+        ),
+        (
+            {"include_rank": True},
+            "FTS4",
+            (
+                "with original as (\n"
+                "    select\n"
+                "        rowid,\n"
+                "        *\n"
+                "    from [books]\n"
+                ")\n"
+                "select\n"
+                "    [original].*,\n"
+                "    rank_bm25(matchinfo([books_fts], 'pcnalx')) rank\n"
+                "from\n"
+                "    [original]\n"
+                "    join [books_fts] on [original].rowid = [books_fts].rowid\n"
+                "where\n"
+                "    [books_fts] match :query\n"
+                "order by\n"
+                "    rank_bm25(matchinfo([books_fts], 'pcnalx'))"
+            ),
+        ),
     ],
 )
 def test_search_sql(kwargs, fts, expected):