Add Java bindings for string literal support in AST

java/src/main/java/ai/rapids/cudf/ast/Literal.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, NVIDIA CORPORATION.
+ * Copyright (c) 2021-2023, NVIDIA CORPORATION.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -200,6 +200,18 @@ public static Literal ofDurationFromLong(DType type, Long value) {
     return ofDurationFromLong(type, value.longValue());
   }
 
+  /** Construct a string literal with the specified value or null. */
+  public static Literal ofString(String value) {
+    if (value == null) {
+      return ofNull(DType.STRING);
+    }
+    byte[] stringBytes = value.getBytes();
+    byte[] serializedValue = new byte[stringBytes.length + Integer.BYTES];
+    ByteBuffer.wrap(serializedValue).order(ByteOrder.nativeOrder()).putInt(stringBytes.length);
+    System.arraycopy(stringBytes, 0, serializedValue, Integer.BYTES, stringBytes.length);
+    return new Literal(DType.STRING, serializedValue);
+  }
+
   Literal(DType type, byte[] serializedValue) {
     this.type = type;
     this.serializedValue = serializedValue;

java/src/main/native/src/CompiledExpression.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021-2022, NVIDIA CORPORATION.
+ * Copyright (c) 2021-2023, NVIDIA CORPORATION.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -15,6 +15,7 @@
  */
 
 #include <cstdint>
+#include <memory>
 #include <stdexcept>
 #include <vector>
 
@@ -56,12 +57,20 @@ class jni_serialized_ast {
 
   /** Read a multi-byte value from the serialized AST data buffer */
   template <typename T> T read() {
-    check_for_eof(sizeof(T));
-    // use memcpy since data may be misaligned
-    T result;
-    memcpy(reinterpret_cast<jbyte *>(&result), data_ptr, sizeof(T));
-    data_ptr += sizeof(T);
-    return result;
+    if constexpr (std::is_same_v<T, std::string>) {
+      auto const size = read<cudf::size_type>();
+      check_for_eof(size);
+      auto const result = std::string(reinterpret_cast<char const *>(data_ptr), size);
+      data_ptr += size;
+      return result;
+    } else {
+      check_for_eof(sizeof(T));
+      // use memcpy since data may be misaligned
+      T result;
+      memcpy(reinterpret_cast<jbyte *>(&result), data_ptr, sizeof(T));
+      data_ptr += sizeof(T);
+      return result;
+    }
   }
 
   /** Decode a libcudf data type from the serialized AST data buffer */
@@ -254,9 +263,29 @@ struct make_literal {
                                      std::move(scalar_ptr));
   }
 
+  /** Construct an AST literal from a string value */
+  template <typename T, std::enable_if_t<std::is_same_v<T, cudf::string_view>> * = nullptr>
+  cudf::ast::literal &operator()(cudf::data_type dtype, bool is_valid,
+                                 cudf::jni::ast::compiled_expr &compiled_expr,
+                                 jni_serialized_ast &jni_ast) {
+    std::unique_ptr<cudf::scalar> scalar_ptr = [&]() {
+      if (is_valid) {
+        std::string val = jni_ast.read<std::string>();
+        return std::make_unique<cudf::string_scalar>(val, is_valid);
+      } else {
+        return std::make_unique<cudf::string_scalar>(rmm::device_buffer{}, is_valid);
+      }
+    }();
+
+    auto &str_scalar = static_cast<cudf::string_scalar &>(*scalar_ptr);
+    return compiled_expr.add_literal(std::make_unique<cudf::ast::literal>(str_scalar),
+                                     std::move(scalar_ptr));
+  }
+
   /** Default functor implementation to catch type dispatch errors */
   template <typename T, std::enable_if_t<!cudf::is_numeric<T>() && !cudf::is_timestamp<T>() &&
-                                         !cudf::is_duration<T>()> * = nullptr>
+                                         !cudf::is_duration<T>() &&
+                                         !std::is_same_v<T, cudf::string_view>> * = nullptr>
   cudf::ast::literal &operator()(cudf::data_type dtype, bool is_valid,
                                  cudf::jni::ast::compiled_expr &compiled_expr,
                                  jni_serialized_ast &jni_ast) {

java/src/test/java/ai/rapids/cudf/ast/CompiledExpressionTest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, NVIDIA CORPORATION.
+ * Copyright (c) 2021-2023, NVIDIA CORPORATION.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -476,6 +476,69 @@ void testBinaryComparisonOperationTransform(BinaryOperator op, Integer[] in1, In
     }
   }
 
+  private static Stream<Arguments> createStringLiteralComparisonParams() {
+    String[] in1 = new String[] {"a", "bb", null, "ccc", "dddd"};
+    String in2 = "ccc";
+    return Stream.of(
+        // nulls compare as equal by default
+        Arguments.of(BinaryOperator.NULL_EQUAL, in1, in2, Arrays.asList(false, false, false, true, false)),
+        Arguments.of(BinaryOperator.NOT_EQUAL, in1, in2, mapArray(in1, (a) -> !a.equals(in2))),
+        Arguments.of(BinaryOperator.LESS, in1, in2, mapArray(in1, (a) -> a.compareTo(in2) < 0)),
+        Arguments.of(BinaryOperator.GREATER, in1, in2, mapArray(in1, (a) -> a.compareTo(in2) > 0)),
+        Arguments.of(BinaryOperator.LESS_EQUAL, in1, in2, mapArray(in1, (a) -> a.compareTo(in2) <= 0)),
+        Arguments.of(BinaryOperator.GREATER_EQUAL, in1, in2, mapArray(in1, (a) -> a.compareTo(in2) >= 0)),
+        // null literal
+        Arguments.of(BinaryOperator.NULL_EQUAL, in1, null, Arrays.asList(false, false, true, false, false)),
+        Arguments.of(BinaryOperator.NOT_EQUAL, in1, null, Arrays.asList(null, null, null, null, null)),
+        Arguments.of(BinaryOperator.LESS, in1, null, Arrays.asList(null, null, null, null, null)));
+  }
+
+  @ParameterizedTest
+  @MethodSource("createStringLiteralComparisonParams")
+  void testStringLiteralComparison(BinaryOperator op, String[] in1, String in2,
+                                               List<Boolean> expectedValues) {
+    Literal lit = Literal.ofString(in2);
+    BinaryOperation expr = new BinaryOperation(op,
+        new ColumnReference(0),
+        lit);
+    try (Table t = new Table.TestBuilder().column(in1).build();
+         CompiledExpression compiledExpr = expr.compile();
+         ColumnVector actual = compiledExpr.computeColumn(t);
+         ColumnVector expected = ColumnVector.fromBoxedBooleans(
+             expectedValues.toArray(new Boolean[0]))) {
+      assertColumnsAreEqual(expected, actual);
+    }
+  }
+
+  private static Stream<Arguments> createBinaryComparisonOperationStringParams() {
+    String[] in1 = new String[] {"a", "bb", null, "ccc", "dddd"};
+    String[] in2 = new String[] {"aa", "b", null, "ccc", "ddd"};
+    return Stream.of(
+        // nulls compare as equal by default
+        Arguments.of(BinaryOperator.NULL_EQUAL, in1, in2, Arrays.asList(false, false, true, true, false)),
+        Arguments.of(BinaryOperator.NOT_EQUAL, in1, in2, mapArray(in1, in2, (a, b) -> !a.equals(b))),
+        Arguments.of(BinaryOperator.LESS, in1, in2, mapArray(in1, in2, (a, b) -> a.compareTo(b) < 0)),
+        Arguments.of(BinaryOperator.GREATER, in1, in2, mapArray(in1, in2, (a, b) -> a.compareTo(b) > 0)),
+        Arguments.of(BinaryOperator.LESS_EQUAL, in1, in2, mapArray(in1, in2, (a, b) -> a.compareTo(b) <= 0)),
+        Arguments.of(BinaryOperator.GREATER_EQUAL, in1, in2, mapArray(in1, in2, (a, b) -> a.compareTo(b) >= 0)));
+  }
+
+  @ParameterizedTest
+  @MethodSource("createBinaryComparisonOperationStringParams")
+  void testBinaryComparisonOperationStringTransform(BinaryOperator op, String[] in1, String[] in2,
+                                               List<Boolean> expectedValues) {
+    BinaryOperation expr = new BinaryOperation(op,
+        new ColumnReference(0),
+        new ColumnReference(1));
+    try (Table t = new Table.TestBuilder().column(in1).column(in2).build();
+         CompiledExpression compiledExpr = expr.compile();
+         ColumnVector actual = compiledExpr.computeColumn(t);
+         ColumnVector expected = ColumnVector.fromBoxedBooleans(
+             expectedValues.toArray(new Boolean[0]))) {
+      assertColumnsAreEqual(expected, actual);
+    }
+  }
+
   private static Stream<Arguments> createBinaryBitwiseOperationParams() {
     Integer[] in1 = new Integer[] { -5, 4, null, 2, -3 };
     Integer[] in2 = new Integer[] { 123, -456, null, 0, -3 };