New ?column__date=yyyy-mm-dd filter

datasette/filters.py

@@ -100,6 +100,7 @@ class Filters:
             where j.value = :{p}
         )""", '{c} contains "{v}"')
     ] if detect_json1() else []) + [
+        TemplatedFilter('date', 'date', 'date({c}) = :{p}', '"{c}" is on date {v}'),
         TemplatedFilter('isnull', 'is null', '"{c}" is null', '{c} is null', no_argument=True),
         TemplatedFilter('notnull', 'is not null', '"{c}" is not null', '{c} is not null', no_argument=True),
         TemplatedFilter('isblank', 'is blank', '("{c}" is null or "{c}" = "")', '{c} is blank', no_argument=True),

docs/json_api.rst

@@ -233,6 +233,9 @@ You can filter the data returned by the table based on column values using a que
 
     This is only available if the ``json1`` SQLite extension is enabled.
 
+``?column__date=value``
+    Column is a datestamp occurring on the specified YYYY-MM-DD date, e.g. ``2018-01-02``.
+
 ``?column__isnull=1``
     Matches rows where the column is null.
 

tests/test_filters.py

@@ -60,6 +60,14 @@ import pytest
         ['foo in (:p0, :p1, :p2)'],
         ["1", "2", "3"]
     ),
+    # date
+    (
+        {
+            "foo__date": "1988-01-01",
+        },
+        ["date(foo) = :p0"],
+        ["1988-01-01"]
+    ),
     # JSON array variants of __in (useful for unexpected characters)
     (
         {