[Core] Support Truncate(0) for metrics

api/src/main/java/org/apache/iceberg/util/BinaryUtil.java

@@ -69,6 +69,9 @@ public static ByteBuffer truncateBinaryUnsafe(ByteBuffer value, int width) {
    * the given input
    */
   public static Literal<ByteBuffer> truncateBinaryMin(Literal<ByteBuffer> input, int length) {
+    if (length == 0) {
+      return null;
+    }
     ByteBuffer inputBuffer = input.value();
     if (length >= inputBuffer.remaining()) {
       return input;
@@ -81,6 +84,9 @@ public static Literal<ByteBuffer> truncateBinaryMin(Literal<ByteBuffer> input, i
    * than the given input
    */
   public static Literal<ByteBuffer> truncateBinaryMax(Literal<ByteBuffer> input, int length) {
+    if (length == 0) {
+      return null;
+    }
     ByteBuffer inputBuffer = input.value();
     if (length >= inputBuffer.remaining()) {
       return input;

api/src/main/java/org/apache/iceberg/util/UnicodeUtil.java

@@ -39,7 +39,7 @@ public static boolean isCharHighSurrogate(char ch) {
    * length
    */
   public static CharSequence truncateString(CharSequence input, int length) {
-    Preconditions.checkArgument(length > 0, "Truncate length should be positive");
+    Preconditions.checkArgument(length >= 0, "Truncate length should be non-negative");
     StringBuilder sb = new StringBuilder(input);
     // Get the number of unicode characters in the input
     int numUniCodeCharacters = sb.codePointCount(0, sb.length());
@@ -60,6 +60,9 @@ public static CharSequence truncateString(CharSequence input, int length) {
    */
   public static Literal<CharSequence> truncateStringMin(Literal<CharSequence> input, int length) {
     // Truncate the input to the specified truncate length.
+    if (length == 0) {
+      return null;
+    }
     CharSequence truncatedInput = truncateString(input.value(), length);
     return Literal.of(truncatedInput);
   }
@@ -69,6 +72,9 @@ public static Literal<CharSequence> truncateStringMin(Literal<CharSequence> inpu
    * of unicode characters in the truncated charSequence is lesser than or equal to length
    */
   public static Literal<CharSequence> truncateStringMax(Literal<CharSequence> input, int length) {
+    if (length == 0) {
+      return null;
+    }
     CharSequence inputCharSeq = input.value();
     // Truncate the input to the specified truncate length.
     StringBuilder truncatedStringBuilder = new StringBuilder(truncateString(inputCharSeq, length));

core/src/main/java/org/apache/iceberg/MetricsModes.java

@@ -94,7 +94,8 @@ public String toString() {
 
   /**
    * Under this mode, value_counts, null_value_counts, nan_value_counts and truncated lower_bounds,
-   * upper_bounds are persisted.
+   * upper_bounds are persisted. If truncate is set to 0 then the no values will be persisted for
+   * binaries or strings.
    */
   public static class Truncate extends ProxySerializableMetricsMode {
     private final int length;
@@ -104,7 +105,7 @@ private Truncate(int length) {
     }
 
     public static Truncate withLength(int length) {
-      Preconditions.checkArgument(length > 0, "Truncate length should be positive");
+      Preconditions.checkArgument(length >= 0, "Truncate length should be non-negative");
       return new Truncate(length);
     }
 

core/src/test/java/org/apache/iceberg/TestMetricsModes.java

@@ -63,6 +63,7 @@ public void testMetricsModeParsing() {
     assertThat(MetricsModes.fromString("nOnE")).isEqualTo(None.get());
     assertThat(MetricsModes.fromString("counts")).isEqualTo(Counts.get());
     assertThat(MetricsModes.fromString("coUntS")).isEqualTo(Counts.get());
+    assertThat(MetricsModes.fromString("truncate(0)")).isEqualTo(Truncate.withLength(0));
     assertThat(MetricsModes.fromString("truncate(1)")).isEqualTo(Truncate.withLength(1));
     assertThat(MetricsModes.fromString("truNcAte(10)")).isEqualTo(Truncate.withLength(10));
     assertThat(MetricsModes.fromString("full")).isEqualTo(Full.get());
@@ -71,9 +72,9 @@ public void testMetricsModeParsing() {
 
   @TestTemplate
   public void testInvalidTruncationLength() {
-    assertThatThrownBy(() -> MetricsModes.fromString("truncate(0)"))
+    assertThatThrownBy(() -> MetricsModes.fromString("truncate(-1)"))
         .isInstanceOf(IllegalArgumentException.class)
-        .hasMessage("Truncate length should be positive");
+        .hasMessage("Truncate length should be non-negative");
   }
 
   @TestTemplate

core/src/test/java/org/apache/iceberg/TestMetricsTruncation.java

@@ -96,6 +96,7 @@ public void testTruncateBinaryMin() {
             "Output must have the first two bytes of the input. A lower bound exists "
                 + "even though the first two bytes are the max value")
         .isEqualTo(0);
+    assertThat(truncateBinaryMin(Literal.of(test2), 0)).isNull();
   }
 
   @Test
@@ -135,6 +136,7 @@ public void testTruncateBinaryMax() {
             "Since a shorter sequence is considered smaller, output must have two bytes "
                 + "and the second byte of the input must be incremented")
         .isEqualTo(0);
+    assertThat(truncateBinaryMax(Literal.of(test4), 0)).isNull();
   }
 
   @SuppressWarnings("checkstyle:AvoidEscapedUnicodeCharacters")
@@ -182,6 +184,7 @@ public void testTruncateStringMin() {
     assertThat(cmp.compare(truncateStringMin(Literal.of(test4), 1).value(), test4_1_expected))
         .as("Output must have the first 4 byte UTF-8 character of the input")
         .isEqualTo(0);
+    assertThat(truncateStringMax(Literal.of(test4), 0)).isNull();
   }
 
   @SuppressWarnings("checkstyle:AvoidEscapedUnicodeCharacters")
@@ -301,5 +304,6 @@ public void testTruncateStringMax() {
             "Test the last character is `Character.MIN_SURROGATE - 1` after truncated, it should be incremented to "
                 + "next valid Unicode scalar value `Character.MAX_SURROGATE + 1`")
         .isEqualTo(0);
+    assertThat(truncateStringMax(Literal.of(test9), 0)).isNull();
   }
 }

orc/src/main/java/org/apache/iceberg/orc/OrcMetrics.java

@@ -335,7 +335,6 @@ private static Object truncateIfNeeded(
     CharSequence charSequence = (CharSequence) value;
     MetricsModes.Truncate truncateMode = (MetricsModes.Truncate) metricsMode;
     int truncateLength = truncateMode.length();
-
     switch (bound) {
       case UPPER:
         return Optional.ofNullable(

parquet/src/main/java/org/apache/iceberg/parquet/ParquetUtil.java

@@ -286,13 +286,19 @@ private static <T> void updateMin(
         int truncateLength = truncateMode.length();
         switch (type.typeId()) {
           case STRING:
-            lowerBounds.put(
-                id, UnicodeUtil.truncateStringMin((Literal<CharSequence>) min, truncateLength));
+            Literal<CharSequence> truncatedStringMin =
+                UnicodeUtil.truncateStringMin((Literal<CharSequence>) min, truncateLength);
+            if (truncatedStringMin != null) {
+              lowerBounds.put(id, truncatedStringMin);
+            }
             break;
           case FIXED:
           case BINARY:
-            lowerBounds.put(
-                id, BinaryUtil.truncateBinaryMin((Literal<ByteBuffer>) min, truncateLength));
+            Literal<ByteBuffer> truncatedBinaryMin =
+                BinaryUtil.truncateBinaryMin((Literal<ByteBuffer>) min, truncateLength);
+            if (truncatedBinaryMin != null) {
+              lowerBounds.put(id, truncatedBinaryMin);
+            }
             break;
           default:
             lowerBounds.put(id, min);
@@ -322,6 +328,7 @@ private static <T> void updateMax(
             if (truncatedMaxString != null) {
               upperBounds.put(id, truncatedMaxString);
             }
+
             break;
           case FIXED:
           case BINARY: