feat(date): add ibis.date(y,m,d) functionality

ref: ibis-project#386

ibis/backends/sqlite/registry.py

@@ -1,6 +1,7 @@
 import sqlalchemy as sa
 import toolz
 from multipledispatch import Dispatcher
+import functools
 
 import ibis
 import ibis.common.exceptions as com
@@ -252,9 +253,22 @@ def _rpad(t, expr):
     return arg + _generic_pad(arg, length, pad)
 
 
+def _date_from_ymd(t, expr):
+    y, m, d = map(t.translate, expr.op().args)
+    ymdstr = sa.func.printf('%04d-%02d-%02d', y, m, d)
+    return sa.func.date(ymdstr)
+
+
+def _string_concat(t, expr):
+    return functools.reduce(
+        lambda x, y: x.concat(y), map(t.translate, expr.op().args[0])
+    )
+
+
 operation_registry.update(
     {
         ops.Cast: _cast,
+        ops.DateFromYMD: _date_from_ymd,
         ops.Substring: _substr,
         ops.StrRight: _string_right,
         ops.StringFind: _string_find,
@@ -265,6 +279,7 @@ def _rpad(t, expr):
         ops.Date: unary(sa.func.date),
         ops.TimestampTruncate: _truncate(sa.func.datetime),
         ops.Strftime: _strftime,
+        ops.StringConcat: _string_concat,
         ops.ExtractYear: _strftime_int('%Y'),
         ops.ExtractMonth: _strftime_int('%m'),
         ops.ExtractDay: _strftime_int('%d'),

ibis/backends/tests/test_temporal.py

@@ -623,3 +623,49 @@ def test_now_from_projection(backend, alltypes):
     now = pd.Timestamp('now')
     year_expected = pd.Series([now.year] * n, name='ts')
     tm.assert_series_equal(ts.dt.year, year_expected)
+
+
+def test_date_literal_ex(con):
+    expr = ibis.date(2022, 2, 4)
+    result = con.execute(expr)
+    assert result.strftime('%Y-%m-%d') == '2022-02-04'
+
+
+def test_date_column_from_ymd(con, alltypes, df):
+    c = alltypes.timestamp_col
+    expr = ibis.date(c.year(), c.month(), c.day())
+    tbl = alltypes[
+        expr.name('timestamp_col'),
+    ]
+    result = con.execute(tbl)
+
+    golden = df.timestamp_col.dt.date.astype('datetime64[ns]')
+    tm.assert_series_equal(golden, result.timestamp_col)
+
+
+def test_date_scalar_from_iso(con):
+    expr = ibis.literal('2022-02-24')
+    expr2 = ibis.date(expr)
+
+    result = con.execute(expr2)
+    assert result.strftime('%Y-%m-%d') == '2022-02-24'
+
+
+def test_date_column_from_iso(con, alltypes, df):
+    expr = (
+        alltypes.year.cast('string')
+        + '-'
+        + alltypes.month.cast('string').lpad(2, '0')
+        + '-13'
+    )
+    expr = ibis.date(expr)
+
+    result = con.execute(expr)
+    golden = (
+        df.year.astype(str)
+        + '-'
+        + df.month.astype(str).str.rjust(2, '0')
+        + '-13'
+    )
+    actual = result.dt.strftime('%Y-%m-%d')
+    tm.assert_series_equal(golden.rename('tmp'), actual)

ibis/expr/api.py

@@ -381,7 +381,13 @@ def timestamp(
     return literal(value, type=dt.Timestamp(timezone=timezone))
 
 
-def date(value: str) -> ir.DateScalar:
+@functools.singledispatch
+def date(value) -> DateValue:
+    raise Exception('notimpl')
+
+
+@date.register(str)
+def _(value: str) -> ir.DateScalar:
     """Return a date literal if `value` is coercible to a date.
 
     Parameters
@@ -399,6 +405,17 @@ def date(value: str) -> ir.DateScalar:
     return literal(value, type=dt.date)
 
 
+@date.register(IntegerColumn)
+@date.register(int)
+def _(year, month, day) -> ir.DateScalar:
+    return ops.DateFromYMD(year, month, day).to_expr()
+
+
+@date.register(StringValue)
+def _(value: StringValue) -> DateValue:
+    return value.cast(dt.date)
+
+
 def time(value: str) -> ir.TimeScalar:
     """Return a time literal if `value` is coercible to a time.
 

ibis/expr/operations/temporal.py

@@ -213,6 +213,14 @@ class Date(UnaryOp):
     output_type = rlz.shape_like('arg', dt.date)
 
 
+@public
+class DateFromYMD(ValueOp):
+    year = rlz.integer
+    month = rlz.integer
+    day = rlz.integer
+    output_type = rlz.shape_like('args', dt.date)
+
+
 @public
 class TimestampFromUNIX(ValueOp):
     arg = rlz.any

ibis/tests/expr/test_temporal.py

@@ -705,3 +705,7 @@ def test_time_truncate(table, operand, unit):
     expr = operand(table).truncate(unit)
     assert isinstance(expr, ir.TimeValue)
     assert isinstance(expr.op(), ops.TimeTruncate)
+
+
+def test_date_literal():
+    ibis.date(2022, 2, 4)