From a9e74fcc1a1df1a0192e918b357e6fef013b9894 Mon Sep 17 00:00:00 2001
From: geruh <imgeru@gmail.com>
Date: Tue, 2 Dec 2025 02:29:41 -0800
Subject: [PATCH 1/6]  Core: Align ContentFile Content Field with REST Spec

---
 .../org/apache/iceberg/ContentFileParser.java | 26 +++++++++-
 .../apache/iceberg/TestContentFileParser.java | 51 +++++++++++++++++++
 2 files changed, 75 insertions(+), 2 deletions(-)

diff --git a/core/src/main/java/org/apache/iceberg/ContentFileParser.java b/core/src/main/java/org/apache/iceberg/ContentFileParser.java
index 0033fa97725a..267dbbe00419 100644
--- a/core/src/main/java/org/apache/iceberg/ContentFileParser.java
+++ b/core/src/main/java/org/apache/iceberg/ContentFileParser.java
@@ -23,6 +23,7 @@
 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import org.apache.iceberg.relocated.com.google.common.base.Preconditions;
 import org.apache.iceberg.types.Types;
@@ -84,7 +85,8 @@ public static void toJson(ContentFile<?> contentFile, PartitionSpec spec, JsonGe
     // as it isn't used and BaseFile constructor doesn't support it.
 
     generator.writeNumberField(SPEC_ID, contentFile.specId());
-    generator.writeStringField(CONTENT, contentFile.content().name());
+    String contentValue = contentFile.content().name().toLowerCase(Locale.ROOT).replace('_', '-');
+    generator.writeStringField(CONTENT, contentValue);
     generator.writeStringField(FILE_PATH, contentFile.location());
     generator.writeStringField(FILE_FORMAT, contentFile.format().name());
 
@@ -147,7 +149,7 @@ public static ContentFile<?> fromJson(JsonNode jsonNode, Map<Integer, PartitionS
     int specId = JsonUtil.getInt(SPEC_ID, jsonNode);
     PartitionSpec spec = specsById.get(specId);
     Preconditions.checkArgument(spec != null, "Invalid partition specId: %s", specId);
-    FileContent fileContent = FileContent.valueOf(JsonUtil.getString(CONTENT, jsonNode));
+    FileContent fileContent = fileContentFromJson(JsonUtil.getString(CONTENT, jsonNode));
     String filePath = JsonUtil.getString(FILE_PATH, jsonNode);
     FileFormat fileFormat = FileFormat.fromString(JsonUtil.getString(FILE_FORMAT, jsonNode));
 
@@ -345,4 +347,24 @@ private static PartitionData partitionFromJson(
 
     return partitionData;
   }
+
+  private static FileContent fileContentFromJson(String content) {
+    Preconditions.checkArgument(content != null, "Invalid file content: null");
+    switch (content) {
+      case "data":
+        return FileContent.DATA;
+      case "position-deletes":
+        return FileContent.POSITION_DELETES;
+      case "equality-deletes":
+        return FileContent.EQUALITY_DELETES;
+      default:
+        // Otherwise, fall back to the enum name
+        try {
+          return FileContent.valueOf(content);
+        } catch (IllegalArgumentException e) {
+          throw new IllegalArgumentException(
+              String.format("Invalid file content value: '%s'", content), e);
+        }
+    }
+  }
 }
diff --git a/core/src/test/java/org/apache/iceberg/TestContentFileParser.java b/core/src/test/java/org/apache/iceberg/TestContentFileParser.java
index b3cca25bdcf0..e4d5b97715d4 100644
--- a/core/src/test/java/org/apache/iceberg/TestContentFileParser.java
+++ b/core/src/test/java/org/apache/iceberg/TestContentFileParser.java
@@ -210,6 +210,57 @@ public void testPartitionArrayRespectsSpecOrder() throws Exception {
     assertThat(deserializedContentFile.partition().get(1, String.class)).isEqualTo("foo");
   }
 
+  @Test
+  public void testInvalidContentType() throws Exception {
+    String jsonStr =
+        "{\"spec-id\":0,"
+            + "\"content\":\"invalid-content\","
+            + "\"file-path\":\"/path/to/file.parquet\","
+            + "\"file-format\":\"PARQUET\","
+            + "\"partition\":{},"
+            + "\"file-size-in-bytes\":1,"
+            + "\"record-count\":1}";
+
+    JsonNode node = JsonUtil.mapper().readTree(jsonStr);
+
+    assertThatThrownBy(
+            () -> ContentFileParser.fromJson(node, Map.of(0, PartitionSpec.unpartitioned())))
+        .isInstanceOf(IllegalArgumentException.class)
+        .hasMessage("Invalid file content value: 'invalid-content'");
+  }
+
+  @ParameterizedTest
+  @MethodSource("enumContentTypeCases")
+  public void testEnumContentTypeSerialization(FileContent content, String expectedJsonContent)
+      throws Exception {
+    String jsonStr =
+        "{\"spec-id\":0,"
+            + "\"content\":\""
+            + content.name()
+            + "\","
+            + "\"file-path\":\"/path/to/data.parquet\","
+            + "\"file-format\":\"PARQUET\","
+            + "\"partition\":{},"
+            + "\"file-size-in-bytes\":1,"
+            + "\"record-count\":1}";
+
+    JsonNode jsonNode = JsonUtil.mapper().readTree(jsonStr);
+    ContentFile<?> deserializedContentFile =
+        ContentFileParser.fromJson(jsonNode, Map.of(0, PartitionSpec.unpartitioned()));
+    assertThat(deserializedContentFile.content()).isEqualTo(content);
+
+    String serializedStr =
+        ContentFileParser.toJson(deserializedContentFile, PartitionSpec.unpartitioned());
+    assertThat(serializedStr).contains("\"content\":\"" + expectedJsonContent + "\"");
+  }
+
+  private static Stream<Arguments> enumContentTypeCases() {
+    return Stream.of(
+        Arguments.of(FileContent.DATA, "data"),
+        Arguments.of(FileContent.POSITION_DELETES, "position-deletes"),
+        Arguments.of(FileContent.EQUALITY_DELETES, "equality-deletes"));
+  }
+
   private static Stream<Arguments> provideSpecAndDataFile() {
     return Stream.of(
         Arguments.of(

From 6f6d4b0b8946904ee8e7bc0bd3f340eddd37d479 Mon Sep 17 00:00:00 2001
From: geruh <imgeru@gmail.com>
Date: Tue, 2 Dec 2025 17:17:47 -0800
Subject: [PATCH 2/6] Update the rest of the test

---
 .../apache/iceberg/TestContentFileParser.java | 30 +++++++++----------
 .../apache/iceberg/TestDataTaskParser.java    |  6 ++--
 .../iceberg/TestFileScanTaskParser.java       | 18 +++++------
 ...TestFetchPlanningResultResponseParser.java |  6 ++--
 .../TestFetchScanTasksResponseParser.java     |  6 ++--
 .../TestPlanTableScanResponseParser.java      | 24 +++++++--------
 6 files changed, 45 insertions(+), 45 deletions(-)

diff --git a/core/src/test/java/org/apache/iceberg/TestContentFileParser.java b/core/src/test/java/org/apache/iceberg/TestContentFileParser.java
index e4d5b97715d4..7357edd6022c 100644
--- a/core/src/test/java/org/apache/iceberg/TestContentFileParser.java
+++ b/core/src/test/java/org/apache/iceberg/TestContentFileParser.java
@@ -109,7 +109,7 @@ public void testDeleteFile(PartitionSpec spec, DeleteFile deleteFile, String exp
   public void testPartitionJsonArrayWrongSize() throws Exception {
     PartitionSpec spec = PartitionSpec.builderFor(TestBase.SCHEMA).identity("data").build();
     String jsonStr =
-        "{\"spec-id\":0,\"content\":\"DATA\",\"file-path\":\"/path/to/data.parquet\","
+        "{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data.parquet\","
             + "\"file-format\":\"PARQUET\",\"partition\":[],\"file-size-in-bytes\":10,"
             + "\"record-count\":1}";
 
@@ -124,7 +124,7 @@ public void testPartitionJsonArrayWrongSize() throws Exception {
   public void testPartitionJsonInvalidType() throws Exception {
     PartitionSpec spec = PartitionSpec.builderFor(TestBase.SCHEMA).identity("data").build();
     String jsonStr =
-        "{\"spec-id\":0,\"content\":\"DATA\",\"file-path\":\"/path/to/data.parquet\","
+        "{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data.parquet\","
             + "\"file-format\":\"PARQUET\",\"partition\":\"invalid\",\"file-size-in-bytes\":10,"
             + "\"record-count\":1}";
 
@@ -139,7 +139,7 @@ public void testPartitionJsonInvalidType() throws Exception {
   public void testParsesFieldIdPartitionMap() throws Exception {
     PartitionSpec spec = PartitionSpec.builderFor(TestBase.SCHEMA).identity("data").build();
     String legacyJson =
-        "{\"spec-id\":0,\"content\":\"DATA\",\"file-path\":\"/path/to/data.parquet\","
+        "{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data.parquet\","
             + "\"file-format\":\"PARQUET\",\"partition\":{\"1000\":\"foo\"},\"file-size-in-bytes\":10,"
             + "\"record-count\":1}";
 
@@ -155,7 +155,7 @@ public void testParsesFieldIdPartitionMap() throws Exception {
   public void testPartitionStructObjectContainsExtraField() throws Exception {
     PartitionSpec spec = PartitionSpec.builderFor(TestBase.SCHEMA).identity("data").build();
     String jsonStr =
-        "{\"spec-id\":0,\"content\":\"DATA\",\"file-path\":\"/path/to/data.parquet\","
+        "{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data.parquet\","
             + "\"file-format\":\"PARQUET\",\"partition\":{\"1000\":\"foo\",\"9999\":\"bar\"},"
             + "\"file-size-in-bytes\":10,\"record-count\":1}";
 
@@ -169,7 +169,7 @@ public void testPartitionStructObjectContainsExtraField() throws Exception {
   public void testPartitionStructObjectEmptyIsNull() throws Exception {
     PartitionSpec spec = PartitionSpec.builderFor(TestBase.SCHEMA).identity("data").build();
     String jsonStr =
-        "{\"spec-id\":0,\"content\":\"DATA\",\"file-path\":\"/path/to/data.parquet\","
+        "{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data.parquet\","
             + "\"file-format\":\"PARQUET\",\"partition\":{},\"file-size-in-bytes\":10,"
             + "\"record-count\":1}";
 
@@ -322,17 +322,17 @@ private static DataFile dataFileWithOnlyNanCounts(PartitionSpec spec) {
 
   private static String dataFileJsonWithRequiredOnly(PartitionSpec spec) {
     if (spec.isUnpartitioned()) {
-      return "{\"spec-id\":0,\"content\":\"DATA\",\"file-path\":\"/path/to/data-a.parquet\",\"file-format\":\"PARQUET\","
+      return "{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data-a.parquet\",\"file-format\":\"PARQUET\","
           + "\"partition\":[],\"file-size-in-bytes\":10,\"record-count\":1,\"sort-order-id\":0}";
     } else {
-      return "{\"spec-id\":0,\"content\":\"DATA\",\"file-path\":\"/path/to/data-a.parquet\",\"file-format\":\"PARQUET\","
+      return "{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data-a.parquet\",\"file-format\":\"PARQUET\","
           + "\"partition\":[1],\"file-size-in-bytes\":10,\"record-count\":1,\"sort-order-id\":0}";
     }
   }
 
   private static String dataFileJsonWithAllOptional(PartitionSpec spec) {
     if (spec.isUnpartitioned()) {
-      return "{\"spec-id\":0,\"content\":\"DATA\",\"file-path\":\"/path/to/data-with-stats.parquet\","
+      return "{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data-with-stats.parquet\","
           + "\"file-format\":\"PARQUET\",\"partition\":[],\"file-size-in-bytes\":350,\"record-count\":10,"
           + "\"column-sizes\":{\"keys\":[3,4],\"values\":[100,200]},"
           + "\"value-counts\":{\"keys\":[3,4],\"values\":[90,180]},"
@@ -343,7 +343,7 @@ private static String dataFileJsonWithAllOptional(PartitionSpec spec) {
           + "\"key-metadata\":\"00000000000000000000000000000000\","
           + "\"split-offsets\":[128,256],\"sort-order-id\":1}";
     } else {
-      return "{\"spec-id\":0,\"content\":\"DATA\",\"file-path\":\"/path/to/data-with-stats.parquet\","
+      return "{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data-with-stats.parquet\","
           + "\"file-format\":\"PARQUET\",\"partition\":[1],\"file-size-in-bytes\":350,\"record-count\":10,"
           + "\"column-sizes\":{\"keys\":[3,4],\"values\":[100,200]},"
           + "\"value-counts\":{\"keys\":[3,4],\"values\":[90,180]},"
@@ -439,7 +439,7 @@ private static DeleteFile deleteFileWithDataRef(PartitionSpec spec) {
   }
 
   private static String deleteFileWithDataRefJson() {
-    return "{\"spec-id\":0,\"content\":\"POSITION_DELETES\",\"file-path\":\"/path/to/delete.parquet\","
+    return "{\"spec-id\":0,\"content\":\"position-deletes\",\"file-path\":\"/path/to/delete.parquet\","
         + "\"file-format\":\"PARQUET\",\"partition\":[4],\"file-size-in-bytes\":1234,"
         + "\"record-count\":10,\"referenced-data-file\":\"/path/to/data/file.parquet\"}";
   }
@@ -465,7 +465,7 @@ private static DeleteFile dv(PartitionSpec spec) {
   }
 
   private static String dvJson() {
-    return "{\"spec-id\":0,\"content\":\"POSITION_DELETES\",\"file-path\":\"/path/to/delete.puffin\","
+    return "{\"spec-id\":0,\"content\":\"position-deletes\",\"file-path\":\"/path/to/delete.puffin\","
         + "\"file-format\":\"PUFFIN\",\"partition\":[4],\"file-size-in-bytes\":1234,\"record-count\":10,"
         + "\"referenced-data-file\":\"/path/to/data/file.parquet\",\"content-offset\":4,\"content-size-in-bytes\":40}";
   }
@@ -538,17 +538,17 @@ private static DeleteFile deleteFileWithAllOptional(PartitionSpec spec) {
 
   private static String deleteFileJsonWithRequiredOnly(PartitionSpec spec) {
     if (spec.isUnpartitioned()) {
-      return "{\"spec-id\":0,\"content\":\"POSITION_DELETES\",\"file-path\":\"/path/to/delete-a.parquet\","
+      return "{\"spec-id\":0,\"content\":\"position-deletes\",\"file-path\":\"/path/to/delete-a.parquet\","
           + "\"file-format\":\"PARQUET\",\"partition\":[],\"file-size-in-bytes\":1234,\"record-count\":9}";
     } else {
-      return "{\"spec-id\":0,\"content\":\"POSITION_DELETES\",\"file-path\":\"/path/to/delete-a.parquet\","
+      return "{\"spec-id\":0,\"content\":\"position-deletes\",\"file-path\":\"/path/to/delete-a.parquet\","
           + "\"file-format\":\"PARQUET\",\"partition\":[9],\"file-size-in-bytes\":1234,\"record-count\":9}";
     }
   }
 
   private static String deleteFileJsonWithAllOptional(PartitionSpec spec) {
     if (spec.isUnpartitioned()) {
-      return "{\"spec-id\":0,\"content\":\"EQUALITY_DELETES\",\"file-path\":\"/path/to/delete-with-stats.parquet\","
+      return "{\"spec-id\":0,\"content\":\"equality-deletes\",\"file-path\":\"/path/to/delete-with-stats.parquet\","
           + "\"file-format\":\"PARQUET\",\"partition\":[],\"file-size-in-bytes\":1234,\"record-count\":10,"
           + "\"column-sizes\":{\"keys\":[3,4],\"values\":[100,200]},"
           + "\"value-counts\":{\"keys\":[3,4],\"values\":[90,180]},"
@@ -559,7 +559,7 @@ private static String deleteFileJsonWithAllOptional(PartitionSpec spec) {
           + "\"key-metadata\":\"00000000000000000000000000000000\","
           + "\"split-offsets\":[128],\"equality-ids\":[3],\"sort-order-id\":1}";
     } else {
-      return "{\"spec-id\":0,\"content\":\"EQUALITY_DELETES\",\"file-path\":\"/path/to/delete-with-stats.parquet\","
+      return "{\"spec-id\":0,\"content\":\"equality-deletes\",\"file-path\":\"/path/to/delete-with-stats.parquet\","
           + "\"file-format\":\"PARQUET\",\"partition\":[9],\"file-size-in-bytes\":1234,\"record-count\":10,"
           + "\"column-sizes\":{\"keys\":[3,4],\"values\":[100,200]},"
           + "\"value-counts\":{\"keys\":[3,4],\"values\":[90,180]},"
diff --git a/core/src/test/java/org/apache/iceberg/TestDataTaskParser.java b/core/src/test/java/org/apache/iceberg/TestDataTaskParser.java
index 758c11db788a..7359b3ebdb75 100644
--- a/core/src/test/java/org/apache/iceberg/TestDataTaskParser.java
+++ b/core/src/test/java/org/apache/iceberg/TestDataTaskParser.java
@@ -144,7 +144,7 @@ public void missingFields() throws Exception {
             + "{\"id\":6,\"name\":\"summary\",\"required\":false,\"type\":{\"type\":\"map\","
             + "\"key-id\":7,\"key\":\"string\",\"value-id\":8,"
             + "\"value\":\"string\",\"value-required\":true}}]},"
-            + "\"metadata-file\":{\"spec-id\":0,\"content\":\"DATA\","
+            + "\"metadata-file\":{\"spec-id\":0,\"content\":\"data\","
             + "\"file-path\":\"/tmp/metadata2.json\","
             + "\"file-format\":\"METADATA\",\"partition\":[],"
             + "\"file-size-in-bytes\":0,\"record-count\":2,\"sort-order-id\":0}"
@@ -172,7 +172,7 @@ public void testDataTaskParsesFieldIdPartitionMap() {
             + "\"fields\":[{\"id\":1,\"name\":\"committed_at\",\"required\":true,\"type\":\"timestamptz\"}]},"
             + "\"projection\":{\"type\":\"struct\",\"schema-id\":0,"
             + "\"fields\":[{\"id\":1,\"name\":\"committed_at\",\"required\":true,\"type\":\"timestamptz\"}]},"
-            + "\"metadata-file\":{\"spec-id\":0,\"content\":\"DATA\",\"file-path\":\"/tmp/metadata.json\","
+            + "\"metadata-file\":{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/tmp/metadata.json\","
             + "\"file-format\":\"METADATA\",\"partition\":{},\"file-size-in-bytes\":0,\"record-count\":1,\"sort-order-id\":0},"
             + "\"rows\":[{\"1\":\"2009-02-13T23:31:30+00:00\"}]}";
 
@@ -263,7 +263,7 @@ private String snapshotsDataTaskJson() {
         + "{\"id\":6,\"name\":\"summary\",\"required\":false,\"type\":{\"type\":\"map\","
         + "\"key-id\":7,\"key\":\"string\",\"value-id\":8,"
         + "\"value\":\"string\",\"value-required\":true}}]},"
-        + "\"metadata-file\":{\"spec-id\":0,\"content\":\"DATA\","
+        + "\"metadata-file\":{\"spec-id\":0,\"content\":\"data\","
         + "\"file-path\":\"/tmp/metadata2.json\","
         + "\"file-format\":\"METADATA\",\"partition\":[],"
         + "\"file-size-in-bytes\":0,\"record-count\":2,\"sort-order-id\":0},"
diff --git a/core/src/test/java/org/apache/iceberg/TestFileScanTaskParser.java b/core/src/test/java/org/apache/iceberg/TestFileScanTaskParser.java
index 882c2b33496d..9c1cd744b2cd 100644
--- a/core/src/test/java/org/apache/iceberg/TestFileScanTaskParser.java
+++ b/core/src/test/java/org/apache/iceberg/TestFileScanTaskParser.java
@@ -96,14 +96,14 @@ private String fileScanTaskJsonWithoutTaskType() {
         + "{\"id\":4,\"name\":\"data\",\"required\":true,\"type\":\"string\"}]},"
         + "\"spec\":{\"spec-id\":0,\"fields\":[{\"name\":\"data_bucket\","
         + "\"transform\":\"bucket[16]\",\"source-id\":4,\"field-id\":1000}]},"
-        + "\"data-file\":{\"spec-id\":0,\"content\":\"DATA\",\"file-path\":\"/path/to/data-a.parquet\","
+        + "\"data-file\":{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data-a.parquet\","
         + "\"file-format\":\"PARQUET\",\"partition\":[0],"
         + "\"file-size-in-bytes\":10,\"record-count\":1,\"sort-order-id\":0},"
         + "\"start\":0,\"length\":10,"
-        + "\"delete-files\":[{\"spec-id\":0,\"content\":\"POSITION_DELETES\","
+        + "\"delete-files\":[{\"spec-id\":0,\"content\":\"position-deletes\","
         + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"PARQUET\","
         + "\"partition\":[0],\"file-size-in-bytes\":10,\"record-count\":1},"
-        + "{\"spec-id\":0,\"content\":\"EQUALITY_DELETES\",\"file-path\":\"/path/to/data-a2-deletes.parquet\","
+        + "{\"spec-id\":0,\"content\":\"equality-deletes\",\"file-path\":\"/path/to/data-a2-deletes.parquet\","
         + "\"file-format\":\"PARQUET\",\"partition\":[0],\"file-size-in-bytes\":10,"
         + "\"record-count\":1,\"equality-ids\":[1],\"sort-order-id\":0}],"
         + "\"residual-filter\":{\"type\":\"eq\",\"term\":\"id\",\"value\":1}}";
@@ -116,14 +116,14 @@ private String fileScanTaskJson() {
         + "{\"id\":4,\"name\":\"data\",\"required\":true,\"type\":\"string\"}]},"
         + "\"spec\":{\"spec-id\":0,\"fields\":[{\"name\":\"data_bucket\","
         + "\"transform\":\"bucket[16]\",\"source-id\":4,\"field-id\":1000}]},"
-        + "\"data-file\":{\"spec-id\":0,\"content\":\"DATA\",\"file-path\":\"/path/to/data-a.parquet\","
+        + "\"data-file\":{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data-a.parquet\","
         + "\"file-format\":\"PARQUET\",\"partition\":[0],"
         + "\"file-size-in-bytes\":10,\"record-count\":1,\"sort-order-id\":0},"
         + "\"start\":0,\"length\":10,"
-        + "\"delete-files\":[{\"spec-id\":0,\"content\":\"POSITION_DELETES\","
+        + "\"delete-files\":[{\"spec-id\":0,\"content\":\"position-deletes\","
         + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"PARQUET\","
         + "\"partition\":[0],\"file-size-in-bytes\":10,\"record-count\":1},"
-        + "{\"spec-id\":0,\"content\":\"EQUALITY_DELETES\",\"file-path\":\"/path/to/data-a2-deletes.parquet\","
+        + "{\"spec-id\":0,\"content\":\"equality-deletes\",\"file-path\":\"/path/to/data-a2-deletes.parquet\","
         + "\"file-format\":\"PARQUET\",\"partition\":[0],\"file-size-in-bytes\":10,"
         + "\"record-count\":1,\"equality-ids\":[1],\"sort-order-id\":0}],"
         + "\"residual-filter\":{\"type\":\"eq\",\"term\":\"id\",\"value\":1}}";
@@ -136,14 +136,14 @@ private String fileScanTaskFieldIdPartitionMapJson() {
         + "{\"id\":4,\"name\":\"data\",\"required\":true,\"type\":\"string\"}]},"
         + "\"spec\":{\"spec-id\":0,\"fields\":[{\"name\":\"data_bucket\","
         + "\"transform\":\"bucket[16]\",\"source-id\":4,\"field-id\":1000}]},"
-        + "\"data-file\":{\"spec-id\":0,\"content\":\"DATA\",\"file-path\":\"/path/to/data-a.parquet\","
+        + "\"data-file\":{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data-a.parquet\","
         + "\"file-format\":\"PARQUET\",\"partition\":{\"1000\":0},"
         + "\"file-size-in-bytes\":10,\"record-count\":1,\"sort-order-id\":0},"
         + "\"start\":0,\"length\":10,"
-        + "\"delete-files\":[{\"spec-id\":0,\"content\":\"POSITION_DELETES\","
+        + "\"delete-files\":[{\"spec-id\":0,\"content\":\"position-deletes\","
         + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"PARQUET\","
         + "\"partition\":{\"1000\":0},\"file-size-in-bytes\":10,\"record-count\":1},"
-        + "{\"spec-id\":0,\"content\":\"EQUALITY_DELETES\",\"file-path\":\"/path/to/data-a2-deletes.parquet\","
+        + "{\"spec-id\":0,\"content\":\"equality-deletes\",\"file-path\":\"/path/to/data-a2-deletes.parquet\","
         + "\"file-format\":\"PARQUET\",\"partition\":{\"1000\":0},\"file-size-in-bytes\":10,"
         + "\"record-count\":1,\"equality-ids\":[1],\"sort-order-id\":0}],"
         + "\"residual-filter\":{\"type\":\"eq\",\"term\":\"id\",\"value\":1}}";
diff --git a/core/src/test/java/org/apache/iceberg/rest/responses/TestFetchPlanningResultResponseParser.java b/core/src/test/java/org/apache/iceberg/rest/responses/TestFetchPlanningResultResponseParser.java
index 8b82e9794d5d..dba45e9935ed 100644
--- a/core/src/test/java/org/apache/iceberg/rest/responses/TestFetchPlanningResultResponseParser.java
+++ b/core/src/test/java/org/apache/iceberg/rest/responses/TestFetchPlanningResultResponseParser.java
@@ -155,7 +155,7 @@ public void roundTripSerdeWithInvalidPlanStatusSubmittedWithDeleteFilesNoFileSca
 
     String invalidJson =
         "{\"status\":\"submitted\","
-            + "\"delete-files\":[{\"spec-id\":0,\"content\":\"POSITION_DELETES\","
+            + "\"delete-files\":[{\"spec-id\":0,\"content\":\"position-deletes\","
             + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"PARQUET\","
             + "\"partition\":[0],\"file-size-in-bytes\":10,\"record-count\":1}]"
             + "}";
@@ -193,11 +193,11 @@ public void roundTripSerdeWithValidStatusAndFileScanTasks() throws JsonProcessin
 
     String expectedToJson =
         "{\"status\":\"completed\","
-            + "\"delete-files\":[{\"spec-id\":0,\"content\":\"POSITION_DELETES\","
+            + "\"delete-files\":[{\"spec-id\":0,\"content\":\"position-deletes\","
             + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"PARQUET\","
             + "\"partition\":[0],\"file-size-in-bytes\":10,\"record-count\":1}],"
             + "\"file-scan-tasks\":["
-            + "{\"data-file\":{\"spec-id\":0,\"content\":\"DATA\",\"file-path\":\"/path/to/data-a.parquet\","
+            + "{\"data-file\":{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data-a.parquet\","
             + "\"file-format\":\"PARQUET\",\"partition\":[0],"
             + "\"file-size-in-bytes\":10,\"record-count\":1,\"sort-order-id\":0},"
             + "\"delete-file-references\":[0],"
diff --git a/core/src/test/java/org/apache/iceberg/rest/responses/TestFetchScanTasksResponseParser.java b/core/src/test/java/org/apache/iceberg/rest/responses/TestFetchScanTasksResponseParser.java
index 62de75e3818b..dfc1bb9f5172 100644
--- a/core/src/test/java/org/apache/iceberg/rest/responses/TestFetchScanTasksResponseParser.java
+++ b/core/src/test/java/org/apache/iceberg/rest/responses/TestFetchScanTasksResponseParser.java
@@ -95,7 +95,7 @@ public void roundTripSerdeWithDeleteFilesNoFileScanTasksPresent() {
 
     String invalidJson =
         "{\"plan-tasks\":[\"task1\",\"task2\"],"
-            + "\"delete-files\":[{\"spec-id\":0,\"content\":\"POSITION_DELETES\","
+            + "\"delete-files\":[{\"spec-id\":0,\"content\":\"position-deletes\","
             + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"PARQUET\","
             + "\"partition\":[0],\"file-size-in-bytes\":10,\"record-count\":1}]"
             + "}";
@@ -129,11 +129,11 @@ public void roundTripSerdeWithFileScanTasks() {
 
     String expectedToJson =
         "{"
-            + "\"delete-files\":[{\"spec-id\":0,\"content\":\"POSITION_DELETES\","
+            + "\"delete-files\":[{\"spec-id\":0,\"content\":\"position-deletes\","
             + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"PARQUET\","
             + "\"partition\":[0],\"file-size-in-bytes\":10,\"record-count\":1}],"
             + "\"file-scan-tasks\":["
-            + "{\"data-file\":{\"spec-id\":0,\"content\":\"DATA\",\"file-path\":\"/path/to/data-a.parquet\","
+            + "{\"data-file\":{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data-a.parquet\","
             + "\"file-format\":\"PARQUET\",\"partition\":[0],"
             + "\"file-size-in-bytes\":10,\"record-count\":1,\"sort-order-id\":0},"
             + "\"delete-file-references\":[0],"
diff --git a/core/src/test/java/org/apache/iceberg/rest/responses/TestPlanTableScanResponseParser.java b/core/src/test/java/org/apache/iceberg/rest/responses/TestPlanTableScanResponseParser.java
index a59bbbd16b45..449b4e36fc0f 100644
--- a/core/src/test/java/org/apache/iceberg/rest/responses/TestPlanTableScanResponseParser.java
+++ b/core/src/test/java/org/apache/iceberg/rest/responses/TestPlanTableScanResponseParser.java
@@ -210,7 +210,7 @@ public void roundTripSerdeWithInvalidPlanStatusSubmittedWithDeleteFilesNoFileSca
     String invalidJson =
         "{\"status\":\"submitted\","
             + "\"plan-id\":\"somePlanId\","
-            + "\"delete-files\":[{\"spec-id\":0,\"content\":\"POSITION_DELETES\","
+            + "\"delete-files\":[{\"spec-id\":0,\"content\":\"position-deletes\","
             + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"PARQUET\","
             + "\"partition\":[0],\"file-size-in-bytes\":10,\"record-count\":1}]"
             + "}";
@@ -244,11 +244,11 @@ public void roundTripSerdeWithValidStatusAndFileScanTasks() {
 
     String expectedToJson =
         "{\"status\":\"completed\","
-            + "\"delete-files\":[{\"spec-id\":0,\"content\":\"POSITION_DELETES\","
+            + "\"delete-files\":[{\"spec-id\":0,\"content\":\"position-deletes\","
             + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"PARQUET\","
             + "\"partition\":[0],\"file-size-in-bytes\":10,\"record-count\":1}],"
             + "\"file-scan-tasks\":["
-            + "{\"data-file\":{\"spec-id\":0,\"content\":\"DATA\",\"file-path\":\"/path/to/data-a.parquet\","
+            + "{\"data-file\":{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data-a.parquet\","
             + "\"file-format\":\"PARQUET\",\"partition\":[0],"
             + "\"file-size-in-bytes\":10,\"record-count\":1,\"sort-order-id\":0},"
             + "\"delete-file-references\":[0],"
@@ -316,7 +316,7 @@ public void multipleTasksWithDifferentDeleteFilesDontAccumulateReferences() {
             + "  \"status\" : \"completed\",\n"
             + "  \"delete-files\" : [ {\n"
             + "    \"spec-id\" : 0,\n"
-            + "    \"content\" : \"POSITION_DELETES\",\n"
+            + "    \"content\" : \"position-deletes\",\n"
             + "    \"file-path\" : \"/path/to/data-a-deletes.parquet\",\n"
             + "    \"file-format\" : \"PARQUET\",\n"
             + "    \"partition\" : [ 0 ],\n"
@@ -324,7 +324,7 @@ public void multipleTasksWithDifferentDeleteFilesDontAccumulateReferences() {
             + "    \"record-count\" : 1\n"
             + "  }, {\n"
             + "    \"spec-id\" : 0,\n"
-            + "    \"content\" : \"POSITION_DELETES\",\n"
+            + "    \"content\" : \"position-deletes\",\n"
             + "    \"file-path\" : \"/path/to/data-b-deletes.parquet\",\n"
             + "    \"file-format\" : \"PARQUET\",\n"
             + "    \"partition\" : [ 1 ],\n"
@@ -332,7 +332,7 @@ public void multipleTasksWithDifferentDeleteFilesDontAccumulateReferences() {
             + "    \"record-count\" : 1\n"
             + "  }, {\n"
             + "    \"spec-id\" : 0,\n"
-            + "    \"content\" : \"EQUALITY_DELETES\",\n"
+            + "    \"content\" : \"equality-deletes\",\n"
             + "    \"file-path\" : \"/path/to/data-c-deletes.parquet\",\n"
             + "    \"file-format\" : \"PARQUET\",\n"
             + "    \"partition\" : [ 2 ],\n"
@@ -344,7 +344,7 @@ public void multipleTasksWithDifferentDeleteFilesDontAccumulateReferences() {
             + "  \"file-scan-tasks\" : [ {\n"
             + "    \"data-file\" : {\n"
             + "      \"spec-id\" : 0,\n"
-            + "      \"content\" : \"DATA\",\n"
+            + "      \"content\" : \"data\",\n"
             + "      \"file-path\" : \"/path/to/data-a.parquet\",\n"
             + "      \"file-format\" : \"PARQUET\",\n"
             + "      \"partition\" : [ 0 ],\n"
@@ -357,7 +357,7 @@ public void multipleTasksWithDifferentDeleteFilesDontAccumulateReferences() {
             + "  }, {\n"
             + "    \"data-file\" : {\n"
             + "      \"spec-id\" : 0,\n"
-            + "      \"content\" : \"DATA\",\n"
+            + "      \"content\" : \"data\",\n"
             + "      \"file-path\" : \"/path/to/data-b.parquet\",\n"
             + "      \"file-format\" : \"PARQUET\",\n"
             + "      \"partition\" : [ 1 ],\n"
@@ -371,7 +371,7 @@ public void multipleTasksWithDifferentDeleteFilesDontAccumulateReferences() {
             + "  }, {\n"
             + "    \"data-file\" : {\n"
             + "      \"spec-id\" : 0,\n"
-            + "      \"content\" : \"DATA\",\n"
+            + "      \"content\" : \"data\",\n"
             + "      \"file-path\" : \"/path/to/data-c.parquet\",\n"
             + "      \"file-format\" : \"PARQUET\",\n"
             + "      \"partition\" : [ 2 ],\n"
@@ -409,7 +409,7 @@ public void roundTripSerdeWithoutDeleteFiles() {
     String expectedJson =
         "{\"status\":\"completed\","
             + "\"file-scan-tasks\":["
-            + "{\"data-file\":{\"spec-id\":0,\"content\":\"DATA\",\"file-path\":\"/path/to/data-a.parquet\","
+            + "{\"data-file\":{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data-a.parquet\","
             + "\"file-format\":\"PARQUET\",\"partition\":[0],"
             + "\"file-size-in-bytes\":10,\"record-count\":1,\"sort-order-id\":0},"
             + "\"residual-filter\":{\"type\":\"eq\",\"term\":\"id\",\"value\":1}}]"
@@ -608,7 +608,7 @@ public void roundTripSerdeWithValidStatusAndFileScanTasksAndCredentials() {
             + "  } ],\n"
             + "  \"delete-files\" : [ {\n"
             + "    \"spec-id\" : 0,\n"
-            + "    \"content\" : \"POSITION_DELETES\",\n"
+            + "    \"content\" : \"position-deletes\",\n"
             + "    \"file-path\" : \"/path/to/data-a-deletes.parquet\",\n"
             + "    \"file-format\" : \"PARQUET\",\n"
             + "    \"partition\" : [ 0 ],\n"
@@ -618,7 +618,7 @@ public void roundTripSerdeWithValidStatusAndFileScanTasksAndCredentials() {
             + "  \"file-scan-tasks\" : [ {\n"
             + "    \"data-file\" : {\n"
             + "      \"spec-id\" : 0,\n"
-            + "      \"content\" : \"DATA\",\n"
+            + "      \"content\" : \"data\",\n"
             + "      \"file-path\" : \"/path/to/data-a.parquet\",\n"
             + "      \"file-format\" : \"PARQUET\",\n"
             + "      \"partition\" : [ 0 ],\n"

From 3afd321d81c1935aec3be2bf4924930a281780b3 Mon Sep 17 00:00:00 2001
From: geruh <imgeru@gmail.com>
Date: Tue, 2 Dec 2025 22:55:14 -0800
Subject: [PATCH 3/6] align file format with rest spec

---
 .../org/apache/iceberg/ContentFileParser.java |  7 ++--
 .../apache/iceberg/TestContentFileParser.java | 34 +++++++++----------
 .../apache/iceberg/TestDataTaskParser.java    |  6 ++--
 .../iceberg/TestFileScanTaskParser.java       | 18 +++++-----
 ...TestFetchPlanningResultResponseParser.java |  6 ++--
 .../TestFetchScanTasksResponseParser.java     |  6 ++--
 .../TestPlanTableScanResponseParser.java      | 24 ++++++-------
 7 files changed, 52 insertions(+), 49 deletions(-)

diff --git a/core/src/main/java/org/apache/iceberg/ContentFileParser.java b/core/src/main/java/org/apache/iceberg/ContentFileParser.java
index 267dbbe00419..982e97586554 100644
--- a/core/src/main/java/org/apache/iceberg/ContentFileParser.java
+++ b/core/src/main/java/org/apache/iceberg/ContentFileParser.java
@@ -85,10 +85,13 @@ public static void toJson(ContentFile<?> contentFile, PartitionSpec spec, JsonGe
     // as it isn't used and BaseFile constructor doesn't support it.
 
     generator.writeNumberField(SPEC_ID, contentFile.specId());
+    // Since 1.11, we serialize content as lowercase kebab-case values like "equality-deletes"
     String contentValue = contentFile.content().name().toLowerCase(Locale.ROOT).replace('_', '-');
     generator.writeStringField(CONTENT, contentValue);
     generator.writeStringField(FILE_PATH, contentFile.location());
-    generator.writeStringField(FILE_FORMAT, contentFile.format().name());
+    // Since 1.11, we serialize format as lower-case strings (e.g., "parquet")
+    String formatValue = contentFile.format().name().toLowerCase(Locale.ROOT);
+    generator.writeStringField(FILE_FORMAT, formatValue);
 
     if (contentFile.partition() != null) {
       generator.writeFieldName(PARTITION);
@@ -358,7 +361,7 @@ private static FileContent fileContentFromJson(String content) {
       case "equality-deletes":
         return FileContent.EQUALITY_DELETES;
       default:
-        // Otherwise, fall back to the enum name
+        // In 1.10 and before, file content is serialized as the FileContent enum value
         try {
           return FileContent.valueOf(content);
         } catch (IllegalArgumentException e) {
diff --git a/core/src/test/java/org/apache/iceberg/TestContentFileParser.java b/core/src/test/java/org/apache/iceberg/TestContentFileParser.java
index 7357edd6022c..b141eeb766fe 100644
--- a/core/src/test/java/org/apache/iceberg/TestContentFileParser.java
+++ b/core/src/test/java/org/apache/iceberg/TestContentFileParser.java
@@ -110,7 +110,7 @@ public void testPartitionJsonArrayWrongSize() throws Exception {
     PartitionSpec spec = PartitionSpec.builderFor(TestBase.SCHEMA).identity("data").build();
     String jsonStr =
         "{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data.parquet\","
-            + "\"file-format\":\"PARQUET\",\"partition\":[],\"file-size-in-bytes\":10,"
+            + "\"file-format\":\"parquet\",\"partition\":[],\"file-size-in-bytes\":10,"
             + "\"record-count\":1}";
 
     JsonNode jsonNode = JsonUtil.mapper().readTree(jsonStr);
@@ -125,7 +125,7 @@ public void testPartitionJsonInvalidType() throws Exception {
     PartitionSpec spec = PartitionSpec.builderFor(TestBase.SCHEMA).identity("data").build();
     String jsonStr =
         "{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data.parquet\","
-            + "\"file-format\":\"PARQUET\",\"partition\":\"invalid\",\"file-size-in-bytes\":10,"
+            + "\"file-format\":\"parquet\",\"partition\":\"invalid\",\"file-size-in-bytes\":10,"
             + "\"record-count\":1}";
 
     JsonNode jsonNode = JsonUtil.mapper().readTree(jsonStr);
@@ -140,7 +140,7 @@ public void testParsesFieldIdPartitionMap() throws Exception {
     PartitionSpec spec = PartitionSpec.builderFor(TestBase.SCHEMA).identity("data").build();
     String legacyJson =
         "{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data.parquet\","
-            + "\"file-format\":\"PARQUET\",\"partition\":{\"1000\":\"foo\"},\"file-size-in-bytes\":10,"
+            + "\"file-format\":\"parquet\",\"partition\":{\"1000\":\"foo\"},\"file-size-in-bytes\":10,"
             + "\"record-count\":1}";
 
     JsonNode jsonNode = JsonUtil.mapper().readTree(legacyJson);
@@ -156,7 +156,7 @@ public void testPartitionStructObjectContainsExtraField() throws Exception {
     PartitionSpec spec = PartitionSpec.builderFor(TestBase.SCHEMA).identity("data").build();
     String jsonStr =
         "{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data.parquet\","
-            + "\"file-format\":\"PARQUET\",\"partition\":{\"1000\":\"foo\",\"9999\":\"bar\"},"
+            + "\"file-format\":\"parquet\",\"partition\":{\"1000\":\"foo\",\"9999\":\"bar\"},"
             + "\"file-size-in-bytes\":10,\"record-count\":1}";
 
     JsonNode jsonNode = JsonUtil.mapper().readTree(jsonStr);
@@ -170,7 +170,7 @@ public void testPartitionStructObjectEmptyIsNull() throws Exception {
     PartitionSpec spec = PartitionSpec.builderFor(TestBase.SCHEMA).identity("data").build();
     String jsonStr =
         "{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data.parquet\","
-            + "\"file-format\":\"PARQUET\",\"partition\":{},\"file-size-in-bytes\":10,"
+            + "\"file-format\":\"parquet\",\"partition\":{},\"file-size-in-bytes\":10,"
             + "\"record-count\":1}";
 
     JsonNode jsonNode = JsonUtil.mapper().readTree(jsonStr);
@@ -216,7 +216,7 @@ public void testInvalidContentType() throws Exception {
         "{\"spec-id\":0,"
             + "\"content\":\"invalid-content\","
             + "\"file-path\":\"/path/to/file.parquet\","
-            + "\"file-format\":\"PARQUET\","
+            + "\"file-format\":\"parquet\","
             + "\"partition\":{},"
             + "\"file-size-in-bytes\":1,"
             + "\"record-count\":1}";
@@ -239,7 +239,7 @@ public void testEnumContentTypeSerialization(FileContent content, String expecte
             + content.name()
             + "\","
             + "\"file-path\":\"/path/to/data.parquet\","
-            + "\"file-format\":\"PARQUET\","
+            + "\"file-format\":\"parquet\","
             + "\"partition\":{},"
             + "\"file-size-in-bytes\":1,"
             + "\"record-count\":1}";
@@ -322,10 +322,10 @@ private static DataFile dataFileWithOnlyNanCounts(PartitionSpec spec) {
 
   private static String dataFileJsonWithRequiredOnly(PartitionSpec spec) {
     if (spec.isUnpartitioned()) {
-      return "{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data-a.parquet\",\"file-format\":\"PARQUET\","
+      return "{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data-a.parquet\",\"file-format\":\"parquet\","
           + "\"partition\":[],\"file-size-in-bytes\":10,\"record-count\":1,\"sort-order-id\":0}";
     } else {
-      return "{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data-a.parquet\",\"file-format\":\"PARQUET\","
+      return "{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data-a.parquet\",\"file-format\":\"parquet\","
           + "\"partition\":[1],\"file-size-in-bytes\":10,\"record-count\":1,\"sort-order-id\":0}";
     }
   }
@@ -333,7 +333,7 @@ private static String dataFileJsonWithRequiredOnly(PartitionSpec spec) {
   private static String dataFileJsonWithAllOptional(PartitionSpec spec) {
     if (spec.isUnpartitioned()) {
       return "{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data-with-stats.parquet\","
-          + "\"file-format\":\"PARQUET\",\"partition\":[],\"file-size-in-bytes\":350,\"record-count\":10,"
+          + "\"file-format\":\"parquet\",\"partition\":[],\"file-size-in-bytes\":350,\"record-count\":10,"
           + "\"column-sizes\":{\"keys\":[3,4],\"values\":[100,200]},"
           + "\"value-counts\":{\"keys\":[3,4],\"values\":[90,180]},"
           + "\"null-value-counts\":{\"keys\":[3,4],\"values\":[10,20]},"
@@ -344,7 +344,7 @@ private static String dataFileJsonWithAllOptional(PartitionSpec spec) {
           + "\"split-offsets\":[128,256],\"sort-order-id\":1}";
     } else {
       return "{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data-with-stats.parquet\","
-          + "\"file-format\":\"PARQUET\",\"partition\":[1],\"file-size-in-bytes\":350,\"record-count\":10,"
+          + "\"file-format\":\"parquet\",\"partition\":[1],\"file-size-in-bytes\":350,\"record-count\":10,"
           + "\"column-sizes\":{\"keys\":[3,4],\"values\":[100,200]},"
           + "\"value-counts\":{\"keys\":[3,4],\"values\":[90,180]},"
           + "\"null-value-counts\":{\"keys\":[3,4],\"values\":[10,20]},"
@@ -440,7 +440,7 @@ private static DeleteFile deleteFileWithDataRef(PartitionSpec spec) {
 
   private static String deleteFileWithDataRefJson() {
     return "{\"spec-id\":0,\"content\":\"position-deletes\",\"file-path\":\"/path/to/delete.parquet\","
-        + "\"file-format\":\"PARQUET\",\"partition\":[4],\"file-size-in-bytes\":1234,"
+        + "\"file-format\":\"parquet\",\"partition\":[4],\"file-size-in-bytes\":1234,"
         + "\"record-count\":10,\"referenced-data-file\":\"/path/to/data/file.parquet\"}";
   }
 
@@ -466,7 +466,7 @@ private static DeleteFile dv(PartitionSpec spec) {
 
   private static String dvJson() {
     return "{\"spec-id\":0,\"content\":\"position-deletes\",\"file-path\":\"/path/to/delete.puffin\","
-        + "\"file-format\":\"PUFFIN\",\"partition\":[4],\"file-size-in-bytes\":1234,\"record-count\":10,"
+        + "\"file-format\":\"puffin\",\"partition\":[4],\"file-size-in-bytes\":1234,\"record-count\":10,"
         + "\"referenced-data-file\":\"/path/to/data/file.parquet\",\"content-offset\":4,\"content-size-in-bytes\":40}";
   }
 
@@ -539,17 +539,17 @@ private static DeleteFile deleteFileWithAllOptional(PartitionSpec spec) {
   private static String deleteFileJsonWithRequiredOnly(PartitionSpec spec) {
     if (spec.isUnpartitioned()) {
       return "{\"spec-id\":0,\"content\":\"position-deletes\",\"file-path\":\"/path/to/delete-a.parquet\","
-          + "\"file-format\":\"PARQUET\",\"partition\":[],\"file-size-in-bytes\":1234,\"record-count\":9}";
+          + "\"file-format\":\"parquet\",\"partition\":[],\"file-size-in-bytes\":1234,\"record-count\":9}";
     } else {
       return "{\"spec-id\":0,\"content\":\"position-deletes\",\"file-path\":\"/path/to/delete-a.parquet\","
-          + "\"file-format\":\"PARQUET\",\"partition\":[9],\"file-size-in-bytes\":1234,\"record-count\":9}";
+          + "\"file-format\":\"parquet\",\"partition\":[9],\"file-size-in-bytes\":1234,\"record-count\":9}";
     }
   }
 
   private static String deleteFileJsonWithAllOptional(PartitionSpec spec) {
     if (spec.isUnpartitioned()) {
       return "{\"spec-id\":0,\"content\":\"equality-deletes\",\"file-path\":\"/path/to/delete-with-stats.parquet\","
-          + "\"file-format\":\"PARQUET\",\"partition\":[],\"file-size-in-bytes\":1234,\"record-count\":10,"
+          + "\"file-format\":\"parquet\",\"partition\":[],\"file-size-in-bytes\":1234,\"record-count\":10,"
           + "\"column-sizes\":{\"keys\":[3,4],\"values\":[100,200]},"
           + "\"value-counts\":{\"keys\":[3,4],\"values\":[90,180]},"
           + "\"null-value-counts\":{\"keys\":[3,4],\"values\":[10,20]},"
@@ -560,7 +560,7 @@ private static String deleteFileJsonWithAllOptional(PartitionSpec spec) {
           + "\"split-offsets\":[128],\"equality-ids\":[3],\"sort-order-id\":1}";
     } else {
       return "{\"spec-id\":0,\"content\":\"equality-deletes\",\"file-path\":\"/path/to/delete-with-stats.parquet\","
-          + "\"file-format\":\"PARQUET\",\"partition\":[9],\"file-size-in-bytes\":1234,\"record-count\":10,"
+          + "\"file-format\":\"parquet\",\"partition\":[9],\"file-size-in-bytes\":1234,\"record-count\":10,"
           + "\"column-sizes\":{\"keys\":[3,4],\"values\":[100,200]},"
           + "\"value-counts\":{\"keys\":[3,4],\"values\":[90,180]},"
           + "\"null-value-counts\":{\"keys\":[3,4],\"values\":[10,20]},"
diff --git a/core/src/test/java/org/apache/iceberg/TestDataTaskParser.java b/core/src/test/java/org/apache/iceberg/TestDataTaskParser.java
index 7359b3ebdb75..03065abe8744 100644
--- a/core/src/test/java/org/apache/iceberg/TestDataTaskParser.java
+++ b/core/src/test/java/org/apache/iceberg/TestDataTaskParser.java
@@ -146,7 +146,7 @@ public void missingFields() throws Exception {
             + "\"value\":\"string\",\"value-required\":true}}]},"
             + "\"metadata-file\":{\"spec-id\":0,\"content\":\"data\","
             + "\"file-path\":\"/tmp/metadata2.json\","
-            + "\"file-format\":\"METADATA\",\"partition\":[],"
+            + "\"file-format\":\"metadata\",\"partition\":[],"
             + "\"file-size-in-bytes\":0,\"record-count\":2,\"sort-order-id\":0}"
             + "}";
     JsonNode missingTableRowsNode = mapper.reader().readTree(missingTableRowsStr);
@@ -173,7 +173,7 @@ public void testDataTaskParsesFieldIdPartitionMap() {
             + "\"projection\":{\"type\":\"struct\",\"schema-id\":0,"
             + "\"fields\":[{\"id\":1,\"name\":\"committed_at\",\"required\":true,\"type\":\"timestamptz\"}]},"
             + "\"metadata-file\":{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/tmp/metadata.json\","
-            + "\"file-format\":\"METADATA\",\"partition\":{},\"file-size-in-bytes\":0,\"record-count\":1,\"sort-order-id\":0},"
+            + "\"file-format\":\"metadata\",\"partition\":{},\"file-size-in-bytes\":0,\"record-count\":1,\"sort-order-id\":0},"
             + "\"rows\":[{\"1\":\"2009-02-13T23:31:30+00:00\"}]}";
 
     StaticDataTask deserializedTask = (StaticDataTask) ScanTaskParser.fromJson(jsonStr, true);
@@ -265,7 +265,7 @@ private String snapshotsDataTaskJson() {
         + "\"value\":\"string\",\"value-required\":true}}]},"
         + "\"metadata-file\":{\"spec-id\":0,\"content\":\"data\","
         + "\"file-path\":\"/tmp/metadata2.json\","
-        + "\"file-format\":\"METADATA\",\"partition\":[],"
+        + "\"file-format\":\"metadata\",\"partition\":[],"
         + "\"file-size-in-bytes\":0,\"record-count\":2,\"sort-order-id\":0},"
         + "\"rows\":[{\"1\":\"2009-02-13T23:31:30+00:00\",\"2\":1,\"4\":\"append\","
         + "\"5\":\"file:/tmp/manifest1.avro\","
diff --git a/core/src/test/java/org/apache/iceberg/TestFileScanTaskParser.java b/core/src/test/java/org/apache/iceberg/TestFileScanTaskParser.java
index 9c1cd744b2cd..1eff487d86cf 100644
--- a/core/src/test/java/org/apache/iceberg/TestFileScanTaskParser.java
+++ b/core/src/test/java/org/apache/iceberg/TestFileScanTaskParser.java
@@ -97,14 +97,14 @@ private String fileScanTaskJsonWithoutTaskType() {
         + "\"spec\":{\"spec-id\":0,\"fields\":[{\"name\":\"data_bucket\","
         + "\"transform\":\"bucket[16]\",\"source-id\":4,\"field-id\":1000}]},"
         + "\"data-file\":{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data-a.parquet\","
-        + "\"file-format\":\"PARQUET\",\"partition\":[0],"
+        + "\"file-format\":\"parquet\",\"partition\":[0],"
         + "\"file-size-in-bytes\":10,\"record-count\":1,\"sort-order-id\":0},"
         + "\"start\":0,\"length\":10,"
         + "\"delete-files\":[{\"spec-id\":0,\"content\":\"position-deletes\","
-        + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"PARQUET\","
+        + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"parquet\","
         + "\"partition\":[0],\"file-size-in-bytes\":10,\"record-count\":1},"
         + "{\"spec-id\":0,\"content\":\"equality-deletes\",\"file-path\":\"/path/to/data-a2-deletes.parquet\","
-        + "\"file-format\":\"PARQUET\",\"partition\":[0],\"file-size-in-bytes\":10,"
+        + "\"file-format\":\"parquet\",\"partition\":[0],\"file-size-in-bytes\":10,"
         + "\"record-count\":1,\"equality-ids\":[1],\"sort-order-id\":0}],"
         + "\"residual-filter\":{\"type\":\"eq\",\"term\":\"id\",\"value\":1}}";
   }
@@ -117,14 +117,14 @@ private String fileScanTaskJson() {
         + "\"spec\":{\"spec-id\":0,\"fields\":[{\"name\":\"data_bucket\","
         + "\"transform\":\"bucket[16]\",\"source-id\":4,\"field-id\":1000}]},"
         + "\"data-file\":{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data-a.parquet\","
-        + "\"file-format\":\"PARQUET\",\"partition\":[0],"
+        + "\"file-format\":\"parquet\",\"partition\":[0],"
         + "\"file-size-in-bytes\":10,\"record-count\":1,\"sort-order-id\":0},"
         + "\"start\":0,\"length\":10,"
         + "\"delete-files\":[{\"spec-id\":0,\"content\":\"position-deletes\","
-        + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"PARQUET\","
+        + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"parquet\","
         + "\"partition\":[0],\"file-size-in-bytes\":10,\"record-count\":1},"
         + "{\"spec-id\":0,\"content\":\"equality-deletes\",\"file-path\":\"/path/to/data-a2-deletes.parquet\","
-        + "\"file-format\":\"PARQUET\",\"partition\":[0],\"file-size-in-bytes\":10,"
+        + "\"file-format\":\"parquet\",\"partition\":[0],\"file-size-in-bytes\":10,"
         + "\"record-count\":1,\"equality-ids\":[1],\"sort-order-id\":0}],"
         + "\"residual-filter\":{\"type\":\"eq\",\"term\":\"id\",\"value\":1}}";
   }
@@ -137,14 +137,14 @@ private String fileScanTaskFieldIdPartitionMapJson() {
         + "\"spec\":{\"spec-id\":0,\"fields\":[{\"name\":\"data_bucket\","
         + "\"transform\":\"bucket[16]\",\"source-id\":4,\"field-id\":1000}]},"
         + "\"data-file\":{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data-a.parquet\","
-        + "\"file-format\":\"PARQUET\",\"partition\":{\"1000\":0},"
+        + "\"file-format\":\"parquet\",\"partition\":{\"1000\":0},"
         + "\"file-size-in-bytes\":10,\"record-count\":1,\"sort-order-id\":0},"
         + "\"start\":0,\"length\":10,"
         + "\"delete-files\":[{\"spec-id\":0,\"content\":\"position-deletes\","
-        + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"PARQUET\","
+        + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"parquet\","
         + "\"partition\":{\"1000\":0},\"file-size-in-bytes\":10,\"record-count\":1},"
         + "{\"spec-id\":0,\"content\":\"equality-deletes\",\"file-path\":\"/path/to/data-a2-deletes.parquet\","
-        + "\"file-format\":\"PARQUET\",\"partition\":{\"1000\":0},\"file-size-in-bytes\":10,"
+        + "\"file-format\":\"parquet\",\"partition\":{\"1000\":0},\"file-size-in-bytes\":10,"
         + "\"record-count\":1,\"equality-ids\":[1],\"sort-order-id\":0}],"
         + "\"residual-filter\":{\"type\":\"eq\",\"term\":\"id\",\"value\":1}}";
   }
diff --git a/core/src/test/java/org/apache/iceberg/rest/responses/TestFetchPlanningResultResponseParser.java b/core/src/test/java/org/apache/iceberg/rest/responses/TestFetchPlanningResultResponseParser.java
index dba45e9935ed..7c1021d4afab 100644
--- a/core/src/test/java/org/apache/iceberg/rest/responses/TestFetchPlanningResultResponseParser.java
+++ b/core/src/test/java/org/apache/iceberg/rest/responses/TestFetchPlanningResultResponseParser.java
@@ -156,7 +156,7 @@ public void roundTripSerdeWithInvalidPlanStatusSubmittedWithDeleteFilesNoFileSca
     String invalidJson =
         "{\"status\":\"submitted\","
             + "\"delete-files\":[{\"spec-id\":0,\"content\":\"position-deletes\","
-            + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"PARQUET\","
+            + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"parquet\","
             + "\"partition\":[0],\"file-size-in-bytes\":10,\"record-count\":1}]"
             + "}";
 
@@ -194,11 +194,11 @@ public void roundTripSerdeWithValidStatusAndFileScanTasks() throws JsonProcessin
     String expectedToJson =
         "{\"status\":\"completed\","
             + "\"delete-files\":[{\"spec-id\":0,\"content\":\"position-deletes\","
-            + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"PARQUET\","
+            + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"parquet\","
             + "\"partition\":[0],\"file-size-in-bytes\":10,\"record-count\":1}],"
             + "\"file-scan-tasks\":["
             + "{\"data-file\":{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data-a.parquet\","
-            + "\"file-format\":\"PARQUET\",\"partition\":[0],"
+            + "\"file-format\":\"parquet\",\"partition\":[0],"
             + "\"file-size-in-bytes\":10,\"record-count\":1,\"sort-order-id\":0},"
             + "\"delete-file-references\":[0],"
             + "\"residual-filter\":{\"type\":\"eq\",\"term\":\"id\",\"value\":1}}]"
diff --git a/core/src/test/java/org/apache/iceberg/rest/responses/TestFetchScanTasksResponseParser.java b/core/src/test/java/org/apache/iceberg/rest/responses/TestFetchScanTasksResponseParser.java
index dfc1bb9f5172..d7824bc6a673 100644
--- a/core/src/test/java/org/apache/iceberg/rest/responses/TestFetchScanTasksResponseParser.java
+++ b/core/src/test/java/org/apache/iceberg/rest/responses/TestFetchScanTasksResponseParser.java
@@ -96,7 +96,7 @@ public void roundTripSerdeWithDeleteFilesNoFileScanTasksPresent() {
     String invalidJson =
         "{\"plan-tasks\":[\"task1\",\"task2\"],"
             + "\"delete-files\":[{\"spec-id\":0,\"content\":\"position-deletes\","
-            + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"PARQUET\","
+            + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"parquet\","
             + "\"partition\":[0],\"file-size-in-bytes\":10,\"record-count\":1}]"
             + "}";
 
@@ -130,11 +130,11 @@ public void roundTripSerdeWithFileScanTasks() {
     String expectedToJson =
         "{"
             + "\"delete-files\":[{\"spec-id\":0,\"content\":\"position-deletes\","
-            + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"PARQUET\","
+            + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"parquet\","
             + "\"partition\":[0],\"file-size-in-bytes\":10,\"record-count\":1}],"
             + "\"file-scan-tasks\":["
             + "{\"data-file\":{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data-a.parquet\","
-            + "\"file-format\":\"PARQUET\",\"partition\":[0],"
+            + "\"file-format\":\"parquet\",\"partition\":[0],"
             + "\"file-size-in-bytes\":10,\"record-count\":1,\"sort-order-id\":0},"
             + "\"delete-file-references\":[0],"
             + "\"residual-filter\":{\"type\":\"eq\",\"term\":\"id\",\"value\":1}}]"
diff --git a/core/src/test/java/org/apache/iceberg/rest/responses/TestPlanTableScanResponseParser.java b/core/src/test/java/org/apache/iceberg/rest/responses/TestPlanTableScanResponseParser.java
index 449b4e36fc0f..e2c9f21dabba 100644
--- a/core/src/test/java/org/apache/iceberg/rest/responses/TestPlanTableScanResponseParser.java
+++ b/core/src/test/java/org/apache/iceberg/rest/responses/TestPlanTableScanResponseParser.java
@@ -211,7 +211,7 @@ public void roundTripSerdeWithInvalidPlanStatusSubmittedWithDeleteFilesNoFileSca
         "{\"status\":\"submitted\","
             + "\"plan-id\":\"somePlanId\","
             + "\"delete-files\":[{\"spec-id\":0,\"content\":\"position-deletes\","
-            + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"PARQUET\","
+            + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"parquet\","
             + "\"partition\":[0],\"file-size-in-bytes\":10,\"record-count\":1}]"
             + "}";
 
@@ -245,11 +245,11 @@ public void roundTripSerdeWithValidStatusAndFileScanTasks() {
     String expectedToJson =
         "{\"status\":\"completed\","
             + "\"delete-files\":[{\"spec-id\":0,\"content\":\"position-deletes\","
-            + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"PARQUET\","
+            + "\"file-path\":\"/path/to/data-a-deletes.parquet\",\"file-format\":\"parquet\","
             + "\"partition\":[0],\"file-size-in-bytes\":10,\"record-count\":1}],"
             + "\"file-scan-tasks\":["
             + "{\"data-file\":{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data-a.parquet\","
-            + "\"file-format\":\"PARQUET\",\"partition\":[0],"
+            + "\"file-format\":\"parquet\",\"partition\":[0],"
             + "\"file-size-in-bytes\":10,\"record-count\":1,\"sort-order-id\":0},"
             + "\"delete-file-references\":[0],"
             + "\"residual-filter\":{\"type\":\"eq\",\"term\":\"id\",\"value\":1}}]"
@@ -318,7 +318,7 @@ public void multipleTasksWithDifferentDeleteFilesDontAccumulateReferences() {
             + "    \"spec-id\" : 0,\n"
             + "    \"content\" : \"position-deletes\",\n"
             + "    \"file-path\" : \"/path/to/data-a-deletes.parquet\",\n"
-            + "    \"file-format\" : \"PARQUET\",\n"
+            + "    \"file-format\" : \"parquet\",\n"
             + "    \"partition\" : [ 0 ],\n"
             + "    \"file-size-in-bytes\" : 10,\n"
             + "    \"record-count\" : 1\n"
@@ -326,7 +326,7 @@ public void multipleTasksWithDifferentDeleteFilesDontAccumulateReferences() {
             + "    \"spec-id\" : 0,\n"
             + "    \"content\" : \"position-deletes\",\n"
             + "    \"file-path\" : \"/path/to/data-b-deletes.parquet\",\n"
-            + "    \"file-format\" : \"PARQUET\",\n"
+            + "    \"file-format\" : \"parquet\",\n"
             + "    \"partition\" : [ 1 ],\n"
             + "    \"file-size-in-bytes\" : 10,\n"
             + "    \"record-count\" : 1\n"
@@ -334,7 +334,7 @@ public void multipleTasksWithDifferentDeleteFilesDontAccumulateReferences() {
             + "    \"spec-id\" : 0,\n"
             + "    \"content\" : \"equality-deletes\",\n"
             + "    \"file-path\" : \"/path/to/data-c-deletes.parquet\",\n"
-            + "    \"file-format\" : \"PARQUET\",\n"
+            + "    \"file-format\" : \"parquet\",\n"
             + "    \"partition\" : [ 2 ],\n"
             + "    \"file-size-in-bytes\" : 10,\n"
             + "    \"record-count\" : 1,\n"
@@ -346,7 +346,7 @@ public void multipleTasksWithDifferentDeleteFilesDontAccumulateReferences() {
             + "      \"spec-id\" : 0,\n"
             + "      \"content\" : \"data\",\n"
             + "      \"file-path\" : \"/path/to/data-a.parquet\",\n"
-            + "      \"file-format\" : \"PARQUET\",\n"
+            + "      \"file-format\" : \"parquet\",\n"
             + "      \"partition\" : [ 0 ],\n"
             + "      \"file-size-in-bytes\" : 10,\n"
             + "      \"record-count\" : 1,\n"
@@ -359,7 +359,7 @@ public void multipleTasksWithDifferentDeleteFilesDontAccumulateReferences() {
             + "      \"spec-id\" : 0,\n"
             + "      \"content\" : \"data\",\n"
             + "      \"file-path\" : \"/path/to/data-b.parquet\",\n"
-            + "      \"file-format\" : \"PARQUET\",\n"
+            + "      \"file-format\" : \"parquet\",\n"
             + "      \"partition\" : [ 1 ],\n"
             + "      \"file-size-in-bytes\" : 10,\n"
             + "      \"record-count\" : 1,\n"
@@ -373,7 +373,7 @@ public void multipleTasksWithDifferentDeleteFilesDontAccumulateReferences() {
             + "      \"spec-id\" : 0,\n"
             + "      \"content\" : \"data\",\n"
             + "      \"file-path\" : \"/path/to/data-c.parquet\",\n"
-            + "      \"file-format\" : \"PARQUET\",\n"
+            + "      \"file-format\" : \"parquet\",\n"
             + "      \"partition\" : [ 2 ],\n"
             + "      \"file-size-in-bytes\" : 10,\n"
             + "      \"record-count\" : 1,\n"
@@ -410,7 +410,7 @@ public void roundTripSerdeWithoutDeleteFiles() {
         "{\"status\":\"completed\","
             + "\"file-scan-tasks\":["
             + "{\"data-file\":{\"spec-id\":0,\"content\":\"data\",\"file-path\":\"/path/to/data-a.parquet\","
-            + "\"file-format\":\"PARQUET\",\"partition\":[0],"
+            + "\"file-format\":\"parquet\",\"partition\":[0],"
             + "\"file-size-in-bytes\":10,\"record-count\":1,\"sort-order-id\":0},"
             + "\"residual-filter\":{\"type\":\"eq\",\"term\":\"id\",\"value\":1}}]"
             + "}";
@@ -610,7 +610,7 @@ public void roundTripSerdeWithValidStatusAndFileScanTasksAndCredentials() {
             + "    \"spec-id\" : 0,\n"
             + "    \"content\" : \"position-deletes\",\n"
             + "    \"file-path\" : \"/path/to/data-a-deletes.parquet\",\n"
-            + "    \"file-format\" : \"PARQUET\",\n"
+            + "    \"file-format\" : \"parquet\",\n"
             + "    \"partition\" : [ 0 ],\n"
             + "    \"file-size-in-bytes\" : 10,\n"
             + "    \"record-count\" : 1\n"
@@ -620,7 +620,7 @@ public void roundTripSerdeWithValidStatusAndFileScanTasksAndCredentials() {
             + "      \"spec-id\" : 0,\n"
             + "      \"content\" : \"data\",\n"
             + "      \"file-path\" : \"/path/to/data-a.parquet\",\n"
-            + "      \"file-format\" : \"PARQUET\",\n"
+            + "      \"file-format\" : \"parquet\",\n"
             + "      \"partition\" : [ 0 ],\n"
             + "      \"file-size-in-bytes\" : 10,\n"
             + "      \"record-count\" : 1,\n"

From d1cf7fcf1b70d6bed6bb02f87d9466b48c0f9567 Mon Sep 17 00:00:00 2001
From: geruh <imgeru@gmail.com>
Date: Tue, 2 Dec 2025 22:56:04 -0800
Subject: [PATCH 4/6] take out e.g.

---
 core/src/main/java/org/apache/iceberg/ContentFileParser.java | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/core/src/main/java/org/apache/iceberg/ContentFileParser.java b/core/src/main/java/org/apache/iceberg/ContentFileParser.java
index 982e97586554..83d8f0f64d38 100644
--- a/core/src/main/java/org/apache/iceberg/ContentFileParser.java
+++ b/core/src/main/java/org/apache/iceberg/ContentFileParser.java
@@ -89,7 +89,7 @@ public static void toJson(ContentFile<?> contentFile, PartitionSpec spec, JsonGe
     String contentValue = contentFile.content().name().toLowerCase(Locale.ROOT).replace('_', '-');
     generator.writeStringField(CONTENT, contentValue);
     generator.writeStringField(FILE_PATH, contentFile.location());
-    // Since 1.11, we serialize format as lower-case strings (e.g., "parquet")
+    // Since 1.11, we serialize format as lower-case strings like "parquet"
     String formatValue = contentFile.format().name().toLowerCase(Locale.ROOT);
     generator.writeStringField(FILE_FORMAT, formatValue);
 

From 309ff17cf2a4a1ceb22e04f583d454c22694bcae Mon Sep 17 00:00:00 2001
From: geruh <imgeru@gmail.com>
Date: Wed, 3 Dec 2025 12:31:26 -0800
Subject: [PATCH 5/6] address comments

---
 .../org/apache/iceberg/ContentFileParser.java   | 17 +++++++++--------
 .../apache/iceberg/TestContentFileParser.java   | 17 +++++++++++++++++
 2 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/core/src/main/java/org/apache/iceberg/ContentFileParser.java b/core/src/main/java/org/apache/iceberg/ContentFileParser.java
index 83d8f0f64d38..0499fef6d90a 100644
--- a/core/src/main/java/org/apache/iceberg/ContentFileParser.java
+++ b/core/src/main/java/org/apache/iceberg/ContentFileParser.java
@@ -51,6 +51,9 @@ public class ContentFileParser {
   private static final String REFERENCED_DATA_FILE = "referenced-data-file";
   private static final String CONTENT_OFFSET = "content-offset";
   private static final String CONTENT_SIZE = "content-size-in-bytes";
+  private static final String CONTENT_DATA = "data";
+  private static final String CONTENT_POSITION_DELETES = "position-deletes";
+  private static final String CONTENT_EQUALITY_DELETES = "equality-deletes";
 
   private ContentFileParser() {}
 
@@ -86,12 +89,11 @@ public static void toJson(ContentFile<?> contentFile, PartitionSpec spec, JsonGe
 
     generator.writeNumberField(SPEC_ID, contentFile.specId());
     // Since 1.11, we serialize content as lowercase kebab-case values like "equality-deletes"
-    String contentValue = contentFile.content().name().toLowerCase(Locale.ROOT).replace('_', '-');
-    generator.writeStringField(CONTENT, contentValue);
+    generator.writeStringField(
+        CONTENT, contentFile.content().name().toLowerCase(Locale.ROOT).replace('_', '-'));
     generator.writeStringField(FILE_PATH, contentFile.location());
     // Since 1.11, we serialize format as lower-case strings like "parquet"
-    String formatValue = contentFile.format().name().toLowerCase(Locale.ROOT);
-    generator.writeStringField(FILE_FORMAT, formatValue);
+    generator.writeStringField(FILE_FORMAT, contentFile.format().name().toLowerCase(Locale.ROOT));
 
     if (contentFile.partition() != null) {
       generator.writeFieldName(PARTITION);
@@ -352,13 +354,12 @@ private static PartitionData partitionFromJson(
   }
 
   private static FileContent fileContentFromJson(String content) {
-    Preconditions.checkArgument(content != null, "Invalid file content: null");
     switch (content) {
-      case "data":
+      case CONTENT_DATA:
         return FileContent.DATA;
-      case "position-deletes":
+      case CONTENT_POSITION_DELETES:
         return FileContent.POSITION_DELETES;
-      case "equality-deletes":
+      case CONTENT_EQUALITY_DELETES:
         return FileContent.EQUALITY_DELETES;
       default:
         // In 1.10 and before, file content is serialized as the FileContent enum value
diff --git a/core/src/test/java/org/apache/iceberg/TestContentFileParser.java b/core/src/test/java/org/apache/iceberg/TestContentFileParser.java
index b141eeb766fe..6fe4f571c871 100644
--- a/core/src/test/java/org/apache/iceberg/TestContentFileParser.java
+++ b/core/src/test/java/org/apache/iceberg/TestContentFileParser.java
@@ -229,6 +229,23 @@ public void testInvalidContentType() throws Exception {
         .hasMessage("Invalid file content value: 'invalid-content'");
   }
 
+  @Test
+  public void testUppercaseFileFormat() throws Exception {
+    String jsonStr =
+        "{\"spec-id\":0,"
+            + "\"content\":\"data\","
+            + "\"file-path\":\"/path/to/file.parquet\","
+            + "\"file-format\":\"PARQUET\","
+            + "\"partition\":{},"
+            + "\"file-size-in-bytes\":1,"
+            + "\"record-count\":1}";
+
+    JsonNode jsonNode = JsonUtil.mapper().readTree(jsonStr);
+    ContentFile<?> deserializedContentFile =
+        ContentFileParser.fromJson(jsonNode, Map.of(0, PartitionSpec.unpartitioned()));
+    assertThat(deserializedContentFile.format()).isEqualTo(FileFormat.PARQUET);
+  }
+
   @ParameterizedTest
   @MethodSource("enumContentTypeCases")
   public void testEnumContentTypeSerialization(FileContent content, String expectedJsonContent)

From 2a30899b340060f2da6224f793cabcf950df2965 Mon Sep 17 00:00:00 2001
From: geruh <imgeru@gmail.com>
Date: Thu, 4 Dec 2025 00:05:00 -0800
Subject: [PATCH 6/6] use locale english

---
 core/src/main/java/org/apache/iceberg/ContentFileParser.java | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/core/src/main/java/org/apache/iceberg/ContentFileParser.java b/core/src/main/java/org/apache/iceberg/ContentFileParser.java
index 0499fef6d90a..f024a24b18ce 100644
--- a/core/src/main/java/org/apache/iceberg/ContentFileParser.java
+++ b/core/src/main/java/org/apache/iceberg/ContentFileParser.java
@@ -90,10 +90,11 @@ public static void toJson(ContentFile<?> contentFile, PartitionSpec spec, JsonGe
     generator.writeNumberField(SPEC_ID, contentFile.specId());
     // Since 1.11, we serialize content as lowercase kebab-case values like "equality-deletes"
     generator.writeStringField(
-        CONTENT, contentFile.content().name().toLowerCase(Locale.ROOT).replace('_', '-'));
+        CONTENT, contentFile.content().name().toLowerCase(Locale.ENGLISH).replace('_', '-'));
     generator.writeStringField(FILE_PATH, contentFile.location());
     // Since 1.11, we serialize format as lower-case strings like "parquet"
-    generator.writeStringField(FILE_FORMAT, contentFile.format().name().toLowerCase(Locale.ROOT));
+    generator.writeStringField(
+        FILE_FORMAT, contentFile.format().name().toLowerCase(Locale.ENGLISH));
 
     if (contentFile.partition() != null) {
       generator.writeFieldName(PARTITION);