[feature](function) support is_valid_utf8 function (#62515)

Add `is_valid_utf8(s)` / `isValidUTF8(s)` function that returns `true`
if the input is valid UTF-8, `false` otherwise. Also adds
`is_valid_utf8()` method to `ColumnStr` for column-level UTF-8
validation.

Author: Mryange

be/src/core/column/column_string.cpp

@@ -36,6 +36,7 @@
 #include "util/simd/bits.h"
 #include "util/simd/vstring_function.h"
 #include "util/unaligned.h"
+#include "util/utf8_check.h"
 namespace doris {
 
 template <typename T>
@@ -759,6 +760,20 @@ bool ColumnStr<T>::is_ascii() const {
     return simd::VStringFunctions::is_ascii(StringRef(chars.data(), chars.size()));
 }
 
+template <typename T>
+bool ColumnStr<T>::is_valid_utf8() const {
+    const auto num_rows = offsets.size();
+    const char* data = reinterpret_cast<const char*>(chars.data());
+    for (size_t i = 0; i < num_rows; ++i) {
+        auto str_offset = offset_at(i);
+        auto str_size = size_at(i);
+        if (!validate_utf8(data + str_offset, str_size)) {
+            return false;
+        }
+    }
+    return true;
+}
+
 template class ColumnStr<uint32_t>;
 template class ColumnStr<uint64_t>;
 } // namespace doris

be/src/core/column/column_string.h

@@ -51,6 +51,9 @@ class Arena;
 class ColumnSorter;
 
 /** Column for String values.
+  * Note: In string functions, we assume that ColumnStr contains valid UTF-8 encoded data.
+  * However, ColumnStr is not guaranteed to always hold valid UTF-8, since it is also used
+  * as a serialization container where the content may be arbitrary binary data.
   */
 template <typename T>
 class ColumnStr final : public COWHelper<IColumn, ColumnStr<T>> {
@@ -536,6 +539,7 @@ class ColumnStr final : public COWHelper<IColumn, ColumnStr<T>> {
     }
 
     bool is_ascii() const;
+    bool is_valid_utf8() const;
 
     Chars& get_chars() { return chars; }
     const Chars& get_chars() const { return chars; }

be/src/exprs/function/function_string.cpp

@@ -44,6 +44,7 @@
 #include "exprs/function/string_hex_util.h"
 #include "util/string_search.hpp"
 #include "util/url_coding.h"
+#include "util/utf8_check.h"
 
 namespace doris {
 struct NameStringASCII {
@@ -225,6 +226,29 @@ struct StringUtf8LengthImpl {
     }
 };
 
+struct NameIsValidUTF8 {
+    static constexpr auto name = "is_valid_utf8";
+};
+
+struct IsValidUTF8Impl {
+    using ReturnType = DataTypeUInt8;
+    static constexpr auto PrimitiveTypeImpl = PrimitiveType::TYPE_STRING;
+    using Type = String;
+    using ReturnColumnType = ColumnUInt8;
+
+    static Status vector(const ColumnString::Chars& data, const ColumnString::Offsets& offsets,
+                         PaddedPODArray<UInt8>& res) {
+        auto size = offsets.size();
+        res.resize(size);
+        for (size_t i = 0; i < size; ++i) {
+            const char* raw_str = reinterpret_cast<const char*>(&data[offsets[i - 1]]);
+            size_t str_size = offsets[i] - offsets[i - 1];
+            res[i] = validate_utf8(raw_str, str_size) ? 1 : 0;
+        }
+        return Status::OK();
+    }
+};
+
 struct NameStartsWith {
     static constexpr auto name = "starts_with";
 };
@@ -1316,6 +1340,7 @@ using FunctionStringLength = FunctionUnaryToType<StringLengthImpl, NameStringLen
 using FunctionCrc32 = FunctionUnaryToType<Crc32Impl, NameCrc32>;
 using FunctionStringUTF8Length = FunctionUnaryToType<StringUtf8LengthImpl, NameStringUtf8Length>;
 using FunctionStringSpace = FunctionUnaryToType<StringSpace, NameStringSpace>;
+using FunctionIsValidUTF8 = FunctionUnaryToType<IsValidUTF8Impl, NameIsValidUTF8>;
 using FunctionStringStartsWith =
         FunctionBinaryToType<DataTypeString, DataTypeString, StringStartsWithImpl, NameStartsWith>;
 using FunctionStringEndsWith =
@@ -1422,7 +1447,9 @@ void register_function_string(SimpleFunctionFactory& factory) {
     factory.register_function<FunctionSubReplace<SubReplaceThreeImpl>>();
     factory.register_function<FunctionSubReplace<SubReplaceFourImpl>>();
     factory.register_function<FunctionOverlay>();
+    factory.register_function<FunctionIsValidUTF8>();
 
+    factory.register_alias(FunctionIsValidUTF8::name, "isValidUTF8");
     factory.register_alias(FunctionToLower::name, "lcase");
     factory.register_alias(FunctionToUpper::name, "ucase");
     factory.register_alias(FunctionStringUTF8Length::name, "character_length");

be/test/core/column/column_string_test.cpp

@@ -1425,4 +1425,89 @@ TEST_F(ColumnStringTest, is_ascii) {
     }
 }
 
+TEST_F(ColumnStringTest, is_valid_utf8) {
+    // all ASCII strings are valid UTF-8
+    {
+        auto column = ColumnString::create();
+        column->insert_data("hello", 5);
+        column->insert_data("world", 5);
+        column->insert_data("123!@#", 6);
+        EXPECT_TRUE(column->is_valid_utf8());
+    }
+    // empty column is valid
+    {
+        auto column = ColumnString::create();
+        EXPECT_TRUE(column->is_valid_utf8());
+    }
+    // empty strings are valid UTF-8
+    {
+        auto column = ColumnString::create();
+        column->insert_data("", 0);
+        column->insert_data("", 0);
+        EXPECT_TRUE(column->is_valid_utf8());
+    }
+    // multi-byte UTF-8 characters
+    {
+        auto column = ColumnString::create();
+        column->insert_data("Hello, 世界", strlen("Hello, 世界"));
+        column->insert_data("こんにちは", strlen("こんにちは"));
+        column->insert_data("😀", strlen("😀"));
+        EXPECT_TRUE(column->is_valid_utf8());
+    }
+    // invalid: lone continuation byte 0x80
+    {
+        auto column = ColumnString::create();
+        const char data[] = {'\x80'};
+        column->insert_data(data, 1);
+        EXPECT_FALSE(column->is_valid_utf8());
+    }
+    // invalid: bad 2-byte sequence 0xC3 0x28
+    {
+        auto column = ColumnString::create();
+        const char data[] = {'\xc3', '\x28'};
+        column->insert_data(data, 2);
+        EXPECT_FALSE(column->is_valid_utf8());
+    }
+    // invalid: overlong encoding 0xC0 0xAF
+    {
+        auto column = ColumnString::create();
+        const char data[] = {'\xc0', '\xaf'};
+        column->insert_data(data, 2);
+        EXPECT_FALSE(column->is_valid_utf8());
+    }
+    // invalid: 0xFE byte
+    {
+        auto column = ColumnString::create();
+        const char data[] = {'\xfe'};
+        column->insert_data(data, 1);
+        EXPECT_FALSE(column->is_valid_utf8());
+    }
+    // invalid: truncated 3-byte sequence 0xE4 0xB8
+    {
+        auto column = ColumnString::create();
+        const char data[] = {'\xe4', '\xb8'};
+        column->insert_data(data, 2);
+        EXPECT_FALSE(column->is_valid_utf8());
+    }
+    // mixed: one invalid byte makes the whole column invalid
+    {
+        auto column = ColumnString::create();
+        column->insert_data("hello", 5);
+        const char bad[] = {'\xff'};
+        column->insert_data(bad, 1);
+        column->insert_data("world", 5);
+        EXPECT_FALSE(column->is_valid_utf8());
+    }
+    // cross-row concatenation: "\xE4" + "\xB8\x96" form valid UTF-8 (世) when
+    // concatenated, but each row is invalid individually. Must validate per-row.
+    {
+        auto column = ColumnString::create();
+        const char row1[] = {'\xe4'};
+        const char row2[] = {'\xb8', '\x96'};
+        column->insert_data(row1, 1);
+        column->insert_data(row2, 2);
+        EXPECT_FALSE(column->is_valid_utf8());
+    }
+}
+
 } // namespace doris

be/test/exprs/function/function_string_test.cpp

@@ -994,6 +994,36 @@ TEST(function_string_test, function_ascii_test) {
     check_function_all_arg_comb<DataTypeInt32, true>(func_name, input_types, data_set);
 }
 
+TEST(function_string_test, function_is_valid_utf8_test) {
+    std::string func_name = "is_valid_utf8";
+
+    InputTypeSet input_types = {PrimitiveType::TYPE_VARCHAR};
+
+    DataSet data_set = {
+            // valid UTF-8 strings
+            {{std::string("hello")}, std::uint8_t(1)},
+            {{std::string("")}, std::uint8_t(1)},
+            {{std::string("Hello, 世界")}, std::uint8_t(1)},
+            {{std::string("こんにちは")}, std::uint8_t(1)},
+            {{std::string("123!@#")}, std::uint8_t(1)},
+            {{std::string("\xc3\xb1")}, std::uint8_t(1)},         // ñ
+            {{std::string("\xe2\x82\xac")}, std::uint8_t(1)},     // €
+            {{std::string("\xf0\x9f\x98\x80")}, std::uint8_t(1)}, // 😀
+            // invalid UTF-8 strings
+            {{std::string("\x80")}, std::uint8_t(0)},             // invalid leading byte
+            {{std::string("\xc3\x28")}, std::uint8_t(0)},         // invalid 2-byte sequence
+            {{std::string("\xe2\x28\xa1")}, std::uint8_t(0)},     // invalid 3-byte sequence
+            {{std::string("\xf0\x28\x8c\xbc")}, std::uint8_t(0)}, // invalid 4-byte sequence
+            {{std::string("\xfe")}, std::uint8_t(0)},             // invalid byte 0xFE
+            {{std::string("\xff")}, std::uint8_t(0)},             // invalid byte 0xFF
+            {{std::string("abc\xc0\xaf")}, std::uint8_t(0)},      // overlong encoding
+            // NULL
+            {{Null()}, Null()},
+    };
+
+    check_function_all_arg_comb<DataTypeUInt8, true>(func_name, input_types, data_set);
+}
+
 TEST(function_string_test, function_char_length_test) {
     std::string func_name = "char_length";
 

fe/fe-core/src/main/java/org/apache/doris/catalog/BuiltinScalarFunctions.java

@@ -278,6 +278,7 @@
 import org.apache.doris.nereids.trees.expressions.functions.scalar.IsIpv6String;
 import org.apache.doris.nereids.trees.expressions.functions.scalar.IsNan;
 import org.apache.doris.nereids.trees.expressions.functions.scalar.IsUuid;
+import org.apache.doris.nereids.trees.expressions.functions.scalar.IsValidUtf8;
 import org.apache.doris.nereids.trees.expressions.functions.scalar.JsonArray;
 import org.apache.doris.nereids.trees.expressions.functions.scalar.JsonArrayIgnoreNull;
 import org.apache.doris.nereids.trees.expressions.functions.scalar.JsonContains;
@@ -837,6 +838,7 @@ public class BuiltinScalarFunctions implements FunctionHelper {
             scalar(IsIpAddressInRange.class, "is_ip_address_in_range"),
             scalar(IsNan.class, "isnan"),
             scalar(IsUuid.class, "is_uuid"),
+            scalar(IsValidUtf8.class, "is_valid_utf8", "isValidUTF8"),
             scalar(IsInf.class, "isinf"),
             scalar(Ipv4CIDRToRange.class, "ipv4_cidr_to_range"),
             scalar(Ipv6CIDRToRange.class, "ipv6_cidr_to_range"),

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/scalar/IsValidUtf8.java

@@ -0,0 +1,76 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+package org.apache.doris.nereids.trees.expressions.functions.scalar;
+
+import org.apache.doris.catalog.FunctionSignature;
+import org.apache.doris.nereids.trees.expressions.Expression;
+import org.apache.doris.nereids.trees.expressions.functions.ExplicitlyCastableSignature;
+import org.apache.doris.nereids.trees.expressions.functions.PropagateNullable;
+import org.apache.doris.nereids.trees.expressions.shape.UnaryExpression;
+import org.apache.doris.nereids.trees.expressions.visitor.ExpressionVisitor;
+import org.apache.doris.nereids.types.BooleanType;
+import org.apache.doris.nereids.types.StringType;
+import org.apache.doris.nereids.types.VarcharType;
+
+import com.google.common.base.Preconditions;
+import com.google.common.collect.ImmutableList;
+
+import java.util.List;
+
+/**
+ * ScalarFunction 'is_valid_utf8'.
+ */
+public class IsValidUtf8 extends ScalarFunction
+        implements UnaryExpression, ExplicitlyCastableSignature, PropagateNullable {
+
+    public static final List<FunctionSignature> SIGNATURES = ImmutableList.of(
+            FunctionSignature.ret(BooleanType.INSTANCE).args(VarcharType.SYSTEM_DEFAULT),
+            FunctionSignature.ret(BooleanType.INSTANCE).args(StringType.INSTANCE)
+    );
+
+    /**
+     * constructor with 1 argument.
+     */
+    public IsValidUtf8(Expression arg) {
+        super("is_valid_utf8", arg);
+    }
+
+    /** constructor for withChildren and reuse signature */
+    private IsValidUtf8(ScalarFunctionParams functionParams) {
+        super(functionParams);
+    }
+
+    /**
+     * withChildren.
+     */
+    @Override
+    public IsValidUtf8 withChildren(List<Expression> children) {
+        Preconditions.checkArgument(children.size() == 1);
+        return new IsValidUtf8(getFunctionParams(children));
+    }
+
+    @Override
+    public List<FunctionSignature> getSignatures() {
+        return SIGNATURES;
+    }
+
+    @Override
+    public <R, C> R accept(ExpressionVisitor<R, C> visitor, C context) {
+        return visitor.visitIsValidUtf8(this, context);
+    }
+}

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/visitor/ScalarFunctionVisitor.java

@@ -298,6 +298,7 @@
 import org.apache.doris.nereids.trees.expressions.functions.scalar.IsIpv6String;
 import org.apache.doris.nereids.trees.expressions.functions.scalar.IsNan;
 import org.apache.doris.nereids.trees.expressions.functions.scalar.IsUuid;
+import org.apache.doris.nereids.trees.expressions.functions.scalar.IsValidUtf8;
 import org.apache.doris.nereids.trees.expressions.functions.scalar.JsonArray;
 import org.apache.doris.nereids.trees.expressions.functions.scalar.JsonArrayIgnoreNull;
 import org.apache.doris.nereids.trees.expressions.functions.scalar.JsonContains;
@@ -1701,6 +1702,10 @@ default R visitIsUuid(IsUuid isUuid, C context) {
         return visitScalarFunction(isUuid, context);
     }
 
+    default R visitIsValidUtf8(IsValidUtf8 isValidUtf8, C context) {
+        return visitScalarFunction(isValidUtf8, context);
+    }
+
     default R visitIsInf(IsInf isInf, C context) {
         return visitScalarFunction(isInf, context);
     }