feat: add literal cast to date

Author: zhjwpku

src/iceberg/expression/literal.cc

@@ -27,6 +27,7 @@
 #include "iceberg/util/checked_cast.h"
 #include "iceberg/util/conversions.h"
 #include "iceberg/util/macros.h"
+#include "iceberg/util/temporal_util.h"
 
 namespace iceberg {
 
@@ -209,8 +210,10 @@ Result<Literal> LiteralCaster::CastFromTimestamp(
   auto timestamp_val = std::get<int64_t>(literal.value_);
 
   switch (target_type->type_id()) {
-    case TypeId::kDate:
-      return NotImplemented("Cast from Timestamp to Date is not implemented yet");
+    case TypeId::kDate: {
+      ICEBERG_ASSIGN_OR_RAISE(auto days, TemporalUtils::ExtractDay(literal));
+      return Literal::Date(std::get<int32_t>(days.value()));
+    }
     case TypeId::kTimestampTz:
       return Literal::TimestampTz(timestamp_val);
     default:
@@ -224,8 +227,10 @@ Result<Literal> LiteralCaster::CastFromTimestampTz(
   auto micros = std::get<int64_t>(literal.value_);
 
   switch (target_type->type_id()) {
-    case TypeId::kDate:
-      return NotImplemented("Cast from TimestampTz to Date is not implemented yet");
+    case TypeId::kDate: {
+      ICEBERG_ASSIGN_OR_RAISE(auto days, TemporalUtils::ExtractDay(literal));
+      return Literal::Date(std::get<int32_t>(days.value()));
+    }
     case TypeId::kTimestamp:
       return Literal::Timestamp(micros);
     default:

src/iceberg/test/literal_test.cc

@@ -689,6 +689,14 @@ INSTANTIATE_TEST_SUITE_P(
                              .source_literal = Literal::Long(42L),
                              .target_type = timestamp_tz(),
                              .expected_literal = Literal::TimestampTz(42L)},
+        CastLiteralTestParam{.test_name = "TimestampToDate",
+                             .source_literal = Literal::Timestamp(1622547800000000),
+                             .target_type = date(),
+                             .expected_literal = Literal::Date(18779)},
+        CastLiteralTestParam{.test_name = "TimestampTzToDate",
+                             .source_literal = Literal::TimestampTz(1622547800000000),
+                             .target_type = date(),
+                             .expected_literal = Literal::Date(18779)},
         // Float cast tests
         CastLiteralTestParam{.test_name = "FloatToDouble",
                              .source_literal = Literal::Float(2.0f),