From a5a4e9b65f6c5d14bea318bccf5f3e73628c6a18 Mon Sep 17 00:00:00 2001
From: Bulat <bulat@ydb.tech>
Date: Wed, 26 Nov 2025 17:35:54 +0300
Subject: [PATCH] Fixed wrong output for large DT64* values in UI (#29524)

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
---
 ydb/core/viewer/viewer_query.h            | 74 ++++++++++++++++++++++-
 ydb/public/sdk/cpp/examples/time/main.cpp |  1 +
 2 files changed, 72 insertions(+), 3 deletions(-)

diff --git a/ydb/core/viewer/viewer_query.h b/ydb/core/viewer/viewer_query.h
index 766b53f0f47b..ee97905f0cc6 100644
--- a/ydb/core/viewer/viewer_query.h
+++ b/ydb/core/viewer/viewer_query.h
@@ -661,6 +661,74 @@ class TJsonQuery : public TViewerPipeClient {
     }
 
 private:
+    std::string WriteTime(ui32 value) {
+        ui32 hour, min, sec;
+
+        Y_ASSERT(value < 86400);
+        hour = value / 3600;
+        value -= hour * 3600;
+        min = value / 60;
+        sec = value - min * 60;
+
+        return TStringBuilder() << LeftPad(hour, 2, '0') << ':' << LeftPad(min, 2, '0') << ':' << LeftPad(sec, 2, '0');
+    }
+
+    std::string FormatDate32(const std::chrono::sys_time<NYdb::TWideDays>& tp) {
+        auto value = tp.time_since_epoch().count();
+
+        i32 year;
+        ui32 month;
+        ui32 day;
+        if (!NKikimr::NMiniKQL::SplitDate32(value, year, month, day)) {
+            return TStringBuilder() << "Error: failed to split Date32: " << value;
+        }
+
+        return TStringBuilder() << year << "-" << LeftPad(month, 2, '0') << '-' << LeftPad(day, 2, '0');
+    }
+
+    std::string FormatDatetime64(const std::chrono::sys_time<NYdb::TWideSeconds>& tp) {
+        auto value = tp.time_since_epoch().count();
+
+        if (Y_UNLIKELY(NUdf::MIN_DATETIME64 > value || value > NUdf::MAX_DATETIME64)) {
+            return TStringBuilder() << "Error: value out of range for Datetime64: " << value << " (min: " << NUdf::MIN_DATETIME64 << ", max: " << NUdf::MAX_DATETIME64 << ")";
+        }
+
+        auto date = value / 86400;
+        value -= date * 86400;
+        if (value < 0) {
+            date -= 1;
+            value += 86400;
+        }
+
+        return TStringBuilder() << FormatDate32(std::chrono::sys_time<NYdb::TWideDays>(NYdb::TWideDays(date))) << 'T' << WriteTime(value) << 'Z';
+    }
+
+    std::string FormatTimestamp64(const std::chrono::sys_time<NYdb::TWideMicroseconds>& tp) {
+        auto value = tp.time_since_epoch().count();
+
+        if (Y_UNLIKELY(NUdf::MIN_TIMESTAMP64 > value || value > NUdf::MAX_TIMESTAMP64)) {
+            return TStringBuilder() << "Error: value out of range for Timestamp64: " << value << " (min: " << NUdf::MIN_TIMESTAMP64 << ", max: " << NUdf::MAX_TIMESTAMP64 << ")";
+        }
+        auto date = value / 86400000000ll;
+        value -= date * 86400000000ll;
+        if (value < 0) {
+            date -= 1;
+            value += 86400000000ll;
+        }
+
+        TStringBuilder out;
+        out << FormatDate32(std::chrono::sys_time<NYdb::TWideDays>(NYdb::TWideDays(date)));
+        out << 'T';
+
+        const ui32 time = static_cast<ui32>(value / 1000000ull);
+        value -= time * 1000000ull;
+        out << WriteTime(time);
+        if (value) {
+            out << '.' << LeftPad(value, 6, '0');
+        }
+        return out << 'Z';
+    }
+
     NJson::TJsonValue ColumnPrimitiveValueToJsonValue(NYdb::TValueParser& valueParser) {
         switch (const auto primitive = valueParser.GetPrimitiveType()) {
             case NYdb::EPrimitiveType::Bool:
@@ -696,11 +764,11 @@ class TJsonQuery : public TViewerPipeClient {
             case NYdb::EPrimitiveType::Interval:
                 return TStringBuilder() << valueParser.GetInterval();
             case NYdb::EPrimitiveType::Date32:
-                return std::format("{:%FT%TZ}", valueParser.GetDate32());
+                return FormatDate32(valueParser.GetDate32());
             case NYdb::EPrimitiveType::Datetime64:
-                return std::format("{:%FT%TZ}", valueParser.GetDatetime64());
+                return FormatDatetime64(valueParser.GetDatetime64());
             case NYdb::EPrimitiveType::Timestamp64:
-                return std::format("{:%FT%TZ}", valueParser.GetTimestamp64());
+                return FormatTimestamp64(valueParser.GetTimestamp64());
             case NYdb::EPrimitiveType::Interval64:
                 return valueParser.GetInterval64().count();
             case NYdb::EPrimitiveType::TzDate:
diff --git a/ydb/public/sdk/cpp/examples/time/main.cpp b/ydb/public/sdk/cpp/examples/time/main.cpp
index befdbae47a0b..3ca760665003 100644
--- a/ydb/public/sdk/cpp/examples/time/main.cpp
+++ b/ydb/public/sdk/cpp/examples/time/main.cpp
@@ -27,6 +27,7 @@ void TimeExample(const std::string& endpoint, const std::string& database) {
             auto ts2 = parser.ColumnParser("ts2").GetTimestamp64();
             auto interval = parser.ColumnParser("interval").GetInterval64();
 
+            // Standard output and std::format can overflow for large timestamps
             std::cout << "ts1: " << ts1 << std::endl;
             std::cout << "ts2: " << ts2 << std::endl;
             std::cout << "interval: " << std::chrono::duration_cast<std::chrono::milliseconds>(interval) << std::endl;