Better sort/sort-desc SQL, avoiding deep nesting - closes #135

Author: simonw

django_sql_dashboard/templates/django_sql_dashboard/widgets/default.html

@@ -45,8 +45,8 @@
           <th alt="{{ column.name }}"
             {% if user_can_execute_sql and column.is_unambiguous and not too_long_so_use_post %}
               data-count-url="{% url 'django_sql_dashboard-index' %}?sql={% filter sign_sql|urlencode %}select "{{ column.name }}", count(*) as n from ({{ result.sql|safe }}) as results group by "{{ column.name }}" order by n desc{% endfilter %}{{ result.extra_qs }}"
-              data-sort-asc-url="{% url 'django_sql_dashboard-index' %}?sql={% filter sign_sql|urlencode %}select * from ({{ result.sql|safe }}) as results order by "{{ column.name }}"{% endfilter %}{{ result.extra_qs }}"
-              data-sort-desc-url="{% url 'django_sql_dashboard-index' %}?sql={% filter sign_sql|urlencode %}select * from ({{ result.sql|safe }}) as results order by "{{ column.name }}" desc{% endfilter %}{{ result.extra_qs }}"
+              data-sort-asc-url="{% url 'django_sql_dashboard-index' %}?sql={% filter sign_sql|urlencode %}{{ column.sort_sql|safe }}{% endfilter %}{{ result.extra_qs }}"
+              data-sort-desc-url="{% url 'django_sql_dashboard-index' %}?sql={% filter sign_sql|urlencode %}{{ column.sort_desc_sql|safe }}{% endfilter %}{{ result.extra_qs }}"
               data-count-distinct-url="{% url 'django_sql_dashboard-index' %}?sql={% filter sign_sql|urlencode %}select count(distinct "{{ column.name }}") from ({{ result.sql|safe }}) as results{% endfilter %}{{ result.extra_qs }}"
             {% endif %}>{{ column.name }}</th>
         {% endfor %}

django_sql_dashboard/utils.py

@@ -105,3 +105,15 @@ def postgresql_reserved_words(connection):
             cursor.execute("select word from pg_get_keywords() where catcode = 'R'")
             _reserved_words = [row[0] for row in cursor.fetchall()]
     return _reserved_words
+
+
+_sort_re = re.compile('(^.*) order by "[^"]+"( desc)?$', re.DOTALL)
+
+
+def apply_sort(sql, sort_column, is_desc=False):
+    match = _sort_re.match(sql)
+    if match is not None:
+        sql = match.group(1)
+    else:
+        sql = "select * from ({}) as results".format(sql)
+    return sql + ' order by "{}"{}'.format(sort_column, " desc" if is_desc else "")

django_sql_dashboard/views.py

@@ -22,6 +22,7 @@
 
 from .models import Dashboard
 from .utils import (
+    apply_sort,
     check_for_base64_upgrade,
     displayable_rows,
     extract_named_parameters,
@@ -268,7 +269,12 @@ def _dashboard_index(
                         )
                     display_rows = displayable_rows(rows[:row_limit])
                     column_details = [
-                        {"name": column, "is_unambiguous": columns.count(column) == 1}
+                        {
+                            "name": column,
+                            "is_unambiguous": columns.count(column) == 1,
+                            "sort_sql": apply_sort(sql, column),
+                            "sort_desc_sql": apply_sort(sql, column, True),
+                        }
                         for column in columns
                     ]
                     query_results.append(

test_project/test_utils.py

@@ -1,6 +1,6 @@
 import pytest
 
-from django_sql_dashboard.utils import is_valid_base64_json
+from django_sql_dashboard.utils import apply_sort, is_valid_base64_json
 
 
 @pytest.mark.parametrize(
@@ -17,3 +17,36 @@
 )
 def test_is_valid_base64_json(input, expected):
     assert is_valid_base64_json(input) == expected
+
+
+@pytest.mark.parametrize(
+    "sql,sort_column,is_desc,expected_sql",
+    (
+        (
+            "select * from foo",
+            "bar",
+            False,
+            'select * from (select * from foo) as results order by "bar"',
+        ),
+        (
+            "select * from foo",
+            "bar",
+            True,
+            'select * from (select * from foo) as results order by "bar" desc',
+        ),
+        (
+            'select * from (select * from foo) as results order by "bar" desc',
+            "bar",
+            False,
+            'select * from (select * from foo) as results order by "bar"',
+        ),
+        (
+            'select * from (select * from foo) as results order by "bar"',
+            "bar",
+            True,
+            'select * from (select * from foo) as results order by "bar" desc',
+        ),
+    ),
+)
+def test_apply_sort(sql, sort_column, is_desc, expected_sql):
+    assert apply_sort(sql, sort_column, is_desc) == expected_sql