YT-19324: move YT provider to ydb/library/yql

This commit is formed by the following script: https://paste.yandex-team.ru/6f92e4b8-efc5-4d34-948b-15ee2accd7e7/text.
This commit has zero effect on all projects that depend on YQL.

The summary of changes:
- `yql/providers/yt -> ydb/library/yql/providers/yt `- the whole implementation of YT provider is moved into YDB code base for further export as a part of YT YQL plugin shared library;
- `yql/providers/stat/{expr_nodes,uploader} -> ydb/library/yql/providers/stat/{expr_nodes,uploader}` - a small interface without implementation and the description of stat expr nodes;
- `yql/core/extract_predicate/ut -> ydb/library/yql/core/extract_predicate/ut`;
- `yql/core/{ut,ut_common} -> ydb/library/yql/core/{ut,ut_common}`;
- `yql/core` is gone;
- `yql/library/url_preprocessing -> ydb/library/yql/core/url_preprocessing`.

**NB**: all new targets inside `ydb/` are under `IF (NOT CMAKE_EXPORT)` clause which disables them from open-source cmake generation and ya make build. They will be enabled in the subsequent commits.

1 files changed, 145 insertions, 0 deletions

diff --git a/yt/cpp/mapreduce/io/yamr_table_reader.cpp b/yt/cpp/mapreduce/io/yamr_table_reader.cpp
new file mode 100644
index 0000000000..6204738e10
--- /dev/null
+++ b/yt/cpp/mapreduce/io/yamr_table_reader.cpp
@@ -0,0 +1,145 @@
+#include "yamr_table_reader.h"
+
+#include <yt/cpp/mapreduce/common/helpers.h>
+#include <yt/cpp/mapreduce/common/retry_lib.h>
+#include <yt/cpp/mapreduce/raw_client/raw_requests.h>
+
+////////////////////////////////////////////////////////////////////
+
+static void CheckedSkip(IInputStream* input, size_t byteCount)
+{
+    size_t skipped = input->Skip(byteCount);
+    Y_ENSURE(skipped == byteCount, "Premature end of YaMR stream");
+}
+
+////////////////////////////////////////////////////////////////////
+
+namespace NYT {
+
+using namespace NYT::NDetail::NRawClient;
+
+////////////////////////////////////////////////////////////////////////////////
+
+TYaMRTableReader::TYaMRTableReader(::TIntrusivePtr<TRawTableReader> input)
+    : TLenvalTableReader(std::move(input))
+{ }
+
+TYaMRTableReader::~TYaMRTableReader()
+{ }
+
+const TYaMRRow& TYaMRTableReader::GetRow() const
+{
+    CheckValidity();
+    if (!RowTaken_) {
+        const_cast<TYaMRTableReader*>(this)->ReadRow();
+    }
+    return Row_;
+}
+
+bool TYaMRTableReader::IsValid() const
+{
+    return Valid_;
+}
+
+void TYaMRTableReader::Next()
+{
+    TLenvalTableReader::Next();
+}
+
+void TYaMRTableReader::NextKey()
+{
+    TLenvalTableReader::NextKey();
+}
+
+ui32 TYaMRTableReader::GetTableIndex() const
+{
+    return TLenvalTableReader::GetTableIndex();
+}
+
+ui32 TYaMRTableReader::GetRangeIndex() const
+{
+    return TLenvalTableReader::GetRangeIndex();
+}
+
+ui64 TYaMRTableReader::GetRowIndex() const
+{
+    return TLenvalTableReader::GetRowIndex();
+}
+
+TMaybe<size_t> TYaMRTableReader::GetReadByteCount() const
+{
+    return TLenvalTableReader::GetReadByteCount();
+}
+
+bool TYaMRTableReader::IsEndOfStream() const
+{
+    return TLenvalTableReader::IsEndOfStream();
+}
+
+bool TYaMRTableReader::IsRawReaderExhausted() const
+{
+    return TLenvalTableReader::IsRawReaderExhausted();
+}
+
+void TYaMRTableReader::ReadField(TString* result, i32 length)
+{
+    result->resize(length);
+    size_t count = Input_.Load(result->begin(), length);
+    Y_ENSURE(count == static_cast<size_t>(length), "Premature end of YaMR stream");
+}
+
+void TYaMRTableReader::ReadRow()
+{
+    while (true) {
+        try {
+            i32 value = static_cast<i32>(Length_);
+            ReadField(&Key_, value);
+            Row_.Key = Key_;
+
+            ReadInteger(&value);
+            ReadField(&SubKey_, value);
+            Row_.SubKey = SubKey_;
+
+            ReadInteger(&value);
+            ReadField(&Value_, value);
+            Row_.Value = Value_;
+
+            RowTaken_ = true;
+
+            // We successfully parsed one more row from the stream,
+            // so reset retry count to their initial value.
+            Input_.ResetRetries();
+
+            break;
+        } catch (const std::exception& ) {
+            if (!TLenvalTableReader::Retry()) {
+                throw;
+            }
+        }
+    }
+}
+
+void TYaMRTableReader::SkipRow()
+{
+    while (true) {
+        try {
+            i32 value = static_cast<i32>(Length_);
+            CheckedSkip(&Input_, value);
+
+            ReadInteger(&value);
+            CheckedSkip(&Input_, value);
+
+            ReadInteger(&value);
+            CheckedSkip(&Input_, value);
+            break;
+        } catch (const std::exception& ) {
+            if (!TLenvalTableReader::Retry()) {
+                throw;
+            }
+        }
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+} // namespace NYT