Feat(DuckDB): Transpile unix_millis to epoch_ms (#6224)

Author: vchan

sqlglot/dialects/duckdb.py

@@ -805,6 +805,7 @@ class Generator(generator.Generator):
                 exp.cast(e.this, exp.DataType.Type.TIMESTAMP),
             ),
             exp.UnixMicros: lambda self, e: self.func("EPOCH_US", _implicit_datetime_cast(e.this)),
+            exp.UnixMillis: lambda self, e: self.func("EPOCH_MS", _implicit_datetime_cast(e.this)),
             exp.UnixToStr: lambda self, e: self.func(
                 "STRFTIME", self.func("TO_TIMESTAMP", e.this), self.format_time(e)
             ),

tests/dialects/test_bigquery.py

@@ -2540,6 +2540,22 @@ def test_unix_micros(self):
             },
         )
 
+    def test_unix_millis(self):
+        self.validate_all(
+            "SELECT UNIX_MILLIS('2008-12-25 15:30:00+00')",
+            write={
+                "bigquery": "SELECT UNIX_MILLIS('2008-12-25 15:30:00+00')",
+                "duckdb": "SELECT EPOCH_MS(CAST('2008-12-25 15:30:00+00' AS TIMESTAMPTZ))",
+            },
+        )
+        self.validate_all(
+            "SELECT UNIX_MILLIS(TIMESTAMP '2008-12-25 15:30:00+00')",
+            write={
+                "bigquery": "SELECT UNIX_MILLIS(CAST('2008-12-25 15:30:00+00' AS TIMESTAMP))",
+                "duckdb": "SELECT EPOCH_MS(CAST('2008-12-25 15:30:00+00' AS TIMESTAMPTZ))",
+            },
+        )
+
     def test_regexp_extract(self):
         self.validate_identity("REGEXP_EXTRACT(x, '(?<)')")
         self.validate_identity("REGEXP_EXTRACT(`foo`, 'bar: (.+?)', 1, 1)")