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, 198 insertions, 0 deletions

diff --git a/yt/cpp/mapreduce/io/lenval_table_reader.cpp b/yt/cpp/mapreduce/io/lenval_table_reader.cpp
new file mode 100644
index 00000000000..98274c79960
--- /dev/null
+++ b/yt/cpp/mapreduce/io/lenval_table_reader.cpp
@@ -0,0 +1,198 @@
+#include "lenval_table_reader.h"
+
+#include <yt/cpp/mapreduce/common/helpers.h>
+
+#include <yt/cpp/mapreduce/interface/logging/yt_log.h>
+
+#include <util/string/printf.h>
+
+namespace NYT {
+
+////////////////////////////////////////////////////////////////////////////////
+
+const i32 CONTROL_ATTR_TABLE_INDEX   = -1;
+const i32 CONTROL_ATTR_KEY_SWITCH    = -2;
+const i32 CONTROL_ATTR_RANGE_INDEX   = -3;
+const i32 CONTROL_ATTR_ROW_INDEX     = -4;
+const i32 CONTROL_ATTR_END_OF_STREAM = -5;
+const i32 CONTROL_ATTR_TABLET_INDEX  = -6;
+
+////////////////////////////////////////////////////////////////////////////////
+
+TLenvalTableReader::TLenvalTableReader(::TIntrusivePtr<TRawTableReader> input)
+    : Input_(std::move(input))
+{
+    TLenvalTableReader::Next();
+}
+
+TLenvalTableReader::~TLenvalTableReader()
+{ }
+
+void TLenvalTableReader::CheckValidity() const
+{
+    if (!IsValid()) {
+        ythrow yexception() << "Iterator is not valid";
+    }
+}
+
+bool TLenvalTableReader::IsValid() const
+{
+    return Valid_;
+}
+
+void TLenvalTableReader::Next()
+{
+    if (!RowTaken_) {
+        SkipRow();
+    }
+
+    CheckValidity();
+
+    if (RowIndex_) {
+        ++*RowIndex_;
+    }
+
+    while (true) {
+        try {
+            i32 value = 0;
+            if (!ReadInteger(&value, true)) {
+                return;
+            }
+
+            while (value < 0 && !IsEndOfStream_) {
+                switch (value) {
+                    case CONTROL_ATTR_KEY_SWITCH:
+                        if (!AtStart_) {
+                            Valid_ = false;
+                            return;
+                        } else {
+                            ReadInteger(&value);
+                        }
+                        break;
+
+                    case CONTROL_ATTR_TABLE_INDEX: {
+                        ui32 tmp = 0;
+                        ReadInteger(&tmp);
+                        TableIndex_ = tmp;
+                        ReadInteger(&value);
+                        break;
+                    }
+                    case CONTROL_ATTR_ROW_INDEX: {
+                        ui64 tmp = 0;
+                        ReadInteger(&tmp);
+                        RowIndex_ = tmp;
+                        ReadInteger(&value);
+                        break;
+                    }
+                    case CONTROL_ATTR_RANGE_INDEX: {
+                        ui32 tmp = 0;
+                        ReadInteger(&tmp);
+                        RangeIndex_ = tmp;
+                        ReadInteger(&value);
+                        break;
+                    }
+                    case CONTROL_ATTR_TABLET_INDEX: {
+                        ui64 tmp = 0;
+                        ReadInteger(&tmp);
+                        TabletIndex_ = tmp;
+                        ReadInteger(&value);
+                        break;
+                    }
+                    case CONTROL_ATTR_END_OF_STREAM: {
+                        IsEndOfStream_ = true;
+                        break;
+                    }
+                    default:
+                        ythrow yexception() <<
+                            Sprintf("Invalid control integer %d in lenval stream", value);
+                }
+            }
+
+            Length_ = static_cast<ui32>(value);
+            RowTaken_ = false;
+            AtStart_ = false;
+        } catch (const std::exception& e) {
+            if (!PrepareRetry()) {
+                throw;
+            }
+            continue;
+        }
+        break;
+    }
+}
+
+bool TLenvalTableReader::Retry()
+{
+    if (PrepareRetry()) {
+        RowTaken_ = true;
+        Next();
+        return true;
+    }
+    return false;
+}
+
+void TLenvalTableReader::NextKey()
+{
+    while (Valid_) {
+        Next();
+    }
+
+    if (Finished_) {
+        return;
+    }
+
+    Valid_ = true;
+
+    if (RowIndex_) {
+        --*RowIndex_;
+    }
+
+    RowTaken_ = true;
+}
+
+ui32 TLenvalTableReader::GetTableIndex() const
+{
+    CheckValidity();
+    return TableIndex_;
+}
+
+ui32 TLenvalTableReader::GetRangeIndex() const
+{
+    CheckValidity();
+    return RangeIndex_.GetOrElse(0);
+}
+
+ui64 TLenvalTableReader::GetRowIndex() const
+{
+    CheckValidity();
+    return RowIndex_.GetOrElse(0UL);
+}
+
+TMaybe<size_t> TLenvalTableReader::GetReadByteCount() const
+{
+    return Input_.GetReadByteCount();
+}
+
+bool TLenvalTableReader::IsEndOfStream() const
+{
+    return IsEndOfStream_;
+}
+
+bool TLenvalTableReader::IsRawReaderExhausted() const
+{
+    return Finished_;
+}
+
+bool TLenvalTableReader::PrepareRetry()
+{
+    if (Input_.Retry(RangeIndex_, RowIndex_)) {
+        RowIndex_.Clear();
+        RangeIndex_.Clear();
+        return true;
+    }
+    return false;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+} // namespace NYT