Fix serialization of decimal type in TTableSchema

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Fix for https://github.com/ytsaurus/ytsaurus/issues/173

---

Pull Request resolved: https://github.com/ytsaurus/ytsaurus/pull/174

Co-authored-by: ermolovd <ermolovd@yandex-team.com>

3 files changed, 60 insertions, 4 deletions

diff --git a/yt/cpp/mapreduce/client/skiff.cpp b/yt/cpp/mapreduce/client/skiff.cpp
index ab133e1ae3..1eb2e80d79 100644
--- a/yt/cpp/mapreduce/client/skiff.cpp
+++ b/yt/cpp/mapreduce/client/skiff.cpp
@@ -108,12 +108,18 @@ NSkiff::TSkiffSchemaPtr CreateSkiffSchema(
     TVector<TSkiffSchemaPtr> skiffColumns;
     for (const auto& column: schema.Columns()) {
         TSkiffSchemaPtr skiffColumn;
+        if (column.Deleted().Defined() && *column.Deleted()) {
+            continue;
+        }
         if (column.Type() == VT_ANY && *column.TypeV3() != *NTi::Optional(NTi::Yson())) {
             // We ignore all complex types until YT-12717 is done.
             return nullptr;
         }
-        if (column.Deleted().Defined() && *column.Deleted()) {
-            continue;
+        if (column.TypeV3()->IsDecimal() ||
+            column.TypeV3()->IsOptional() && column.TypeV3()->AsOptional()->GetItemType()->IsDecimal())
+        {
+            // Complex logic for decimal types, ignore them for now.
+            return nullptr;
         }
         if (column.Required() || NTi::IsSingular(column.TypeV3()->GetTypeName())) {
             skiffColumn = CreateSimpleTypeSchema(ValueTypeToSkiffType(column.Type()));
diff --git a/yt/cpp/mapreduce/interface/common_ut.cpp b/yt/cpp/mapreduce/interface/common_ut.cpp
index 3f19433816..f9f0664039 100644
--- a/yt/cpp/mapreduce/interface/common_ut.cpp
+++ b/yt/cpp/mapreduce/interface/common_ut.cpp
@@ -176,6 +176,45 @@ Y_UNIT_TEST_SUITE(Common)
         UNIT_ASSERT_EXCEPTION(checkSortBy(schema, {"a", "junk"}), yexception);
     }
 
+    Y_UNIT_TEST(TTableSchema_Decimal)
+    {
+        NYT::TTableSchema tableSchema;
+
+        tableSchema.AddColumn("a", NTi::Decimal(35, 18));
+        tableSchema.AddColumn("b", NTi::Optional(NTi::Decimal(35, 18)));
+        tableSchema.AddColumn("c", NTi::List(NTi::Decimal(35, 18)));
+
+        auto tableSchemaNode = tableSchema.ToNode();
+        const auto& tableSchemaNodeList = tableSchemaNode.AsList();
+
+        // There was a bug in the serialization of decimal type: https://github.com/ytsaurus/ytsaurus/issues/173
+        {
+            const auto& currentType = tableSchemaNodeList[0];
+            UNIT_ASSERT_VALUES_EQUAL(currentType.ChildAsString("type"), "string");
+            UNIT_ASSERT(currentType.ChildAsBool("required"));
+            UNIT_ASSERT(currentType.HasKey("type_v3"));
+            UNIT_ASSERT_VALUES_EQUAL(currentType.At("type_v3").ChildAsString("type_name"), "decimal");
+        }
+        {
+            const auto& currentType = tableSchemaNodeList[1];
+            UNIT_ASSERT_VALUES_EQUAL(currentType.ChildAsString("type"), "string");
+            UNIT_ASSERT(!currentType.ChildAsBool("required"));
+            UNIT_ASSERT(currentType.HasKey("type_v3"));
+            UNIT_ASSERT_VALUES_EQUAL(currentType.At("type_v3").ChildAsString("type_name"), "optional");
+            UNIT_ASSERT_VALUES_EQUAL(currentType.At("type_v3").At("item").ChildAsString("type_name"), "decimal");
+        }
+        {
+            const auto& currentType = tableSchemaNodeList[2];
+            UNIT_ASSERT_VALUES_EQUAL(currentType.ChildAsString("type"), "any");
+            UNIT_ASSERT(currentType.ChildAsBool("required"));
+            UNIT_ASSERT(currentType.HasKey("type_v3"));
+            UNIT_ASSERT_VALUES_EQUAL(currentType.At("type_v3").ChildAsString("type_name"), "list");
+            UNIT_ASSERT_VALUES_EQUAL(currentType.At("type_v3").At("item").ChildAsString("type_name"), "decimal");
+        }
+
+        UNIT_ASSERT_EQUAL(tableSchema, TTableSchema::FromNode(tableSchemaNode));
+    }
+
     Y_UNIT_TEST(TColumnSchema_TypeV3)
     {
         {
@@ -198,6 +237,11 @@ Y_UNIT_TEST_SUITE(Common)
             UNIT_ASSERT_VALUES_EQUAL(column.Required(), false);
             UNIT_ASSERT_VALUES_EQUAL(column.Type(), VT_ANY);
         }
+        {
+            auto column = TColumnSchema().Type(NTi::Decimal(35, 18));
+            UNIT_ASSERT_VALUES_EQUAL(column.Required(), true);
+            UNIT_ASSERT_VALUES_EQUAL(column.Type(), VT_STRING);
+        }
     }
 
     Y_UNIT_TEST(ToTypeV3)
diff --git a/yt/cpp/mapreduce/interface/serialize.cpp b/yt/cpp/mapreduce/interface/serialize.cpp
index 7cd8417487..8e701d30b4 100644
--- a/yt/cpp/mapreduce/interface/serialize.cpp
+++ b/yt/cpp/mapreduce/interface/serialize.cpp
@@ -165,10 +165,16 @@ void Serialize(const TColumnSchema& columnSchema, NYson::IYsonConsumer* consumer
         .Item("name").Value(columnSchema.Name())
         .DoIf(!columnSchema.RawTypeV3().Defined(),
             [&] (TFluentMap fluent) {
+                static const auto optionalYson = NTi::Optional(NTi::Yson());
+
                 fluent.Item("type").Value(NDetail::ToString(columnSchema.Type()));
                 fluent.Item("required").Value(columnSchema.Required());
-                if (columnSchema.Type() == VT_ANY
-                    && *columnSchema.TypeV3() != *NTi::Optional(NTi::Yson()))
+                if (
+                    (columnSchema.Type() == VT_ANY && *columnSchema.TypeV3() != *optionalYson) ||
+                    // See https://github.com/ytsaurus/ytsaurus/issues/173
+                    columnSchema.TypeV3()->IsDecimal() ||
+                    (columnSchema.TypeV3()->IsOptional() && columnSchema.TypeV3()->AsOptional()->GetItemType()->IsDecimal()))
+
                 {
                     // A lot of user canonize serialized schema.
                     // To be backward compatible we only set type_v3 for new types.