From 08d7d8564c1a311116949d561fc122ee7c138f09 Mon Sep 17 00:00:00 2001
From: Eduard Tudenhoefner <etudenhoefner@gmail.com>
Date: Tue, 17 Sep 2024 11:16:43 +0200
Subject: [PATCH] Core: Update metadata location without updating
 lastUpdatedMillis

Using `TableMetadata.buildFrom(metadata).withMetadataLocation(metadataLocation).build()` would do the following things:
- update `lastUpdatedMillis`
- write a new `metadata-log` entry

However, in `LoadTableResponse` the goal is to only update the metadata location without updating the two mentioned things above.

updates
---
 .../org/apache/iceberg/TableMetadata.java     |  9 +++++
 .../org/apache/iceberg/TestTableMetadata.java | 34 +++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/core/src/main/java/org/apache/iceberg/TableMetadata.java b/core/src/main/java/org/apache/iceberg/TableMetadata.java
index c0bb16bc109d..d20dd59d2b97 100644
--- a/core/src/main/java/org/apache/iceberg/TableMetadata.java
+++ b/core/src/main/java/org/apache/iceberg/TableMetadata.java
@@ -966,6 +966,15 @@ private Builder(TableMetadata base) {
 
     public Builder withMetadataLocation(String newMetadataLocation) {
       this.metadataLocation = newMetadataLocation;
+      if (null != base) {
+        // carry over lastUpdatedMillis from base and set previousFileLocation to null to avoid
+        // writing a new metadata log entry
+        // this is safe since setting metadata location doesn't cause any changes and no other
+        // changes can be added when metadata location is configured
+        this.lastUpdatedMillis = base.lastUpdatedMillis();
+        this.previousFileLocation = null;
+      }
+
       return this;
     }
 
diff --git a/core/src/test/java/org/apache/iceberg/TestTableMetadata.java b/core/src/test/java/org/apache/iceberg/TestTableMetadata.java
index bcde7a7f31d3..5ada35765773 100644
--- a/core/src/test/java/org/apache/iceberg/TestTableMetadata.java
+++ b/core/src/test/java/org/apache/iceberg/TestTableMetadata.java
@@ -1685,4 +1685,38 @@ public void testV3TimestampNanoTypeSupport() {
         ImmutableMap.of(),
         3);
   }
+
+  @Test
+  public void onlyMetadataLocationIsUpdatedWithoutTimestampAndMetadataLogEntry() {
+    String uuid = "386b9f01-002b-4d8c-b77f-42c3fd3b7c9b";
+    TableMetadata metadata =
+        TableMetadata.buildFromEmpty()
+            .assignUUID(uuid)
+            .setLocation("location")
+            .setCurrentSchema(TEST_SCHEMA, 3)
+            .addPartitionSpec(PartitionSpec.unpartitioned())
+            .addSortOrder(SortOrder.unsorted())
+            .discardChanges()
+            .withMetadataLocation("original-metadata-location")
+            .build();
+
+    assertThat(metadata.previousFiles()).isEmpty();
+    assertThat(metadata.metadataFileLocation()).isEqualTo("original-metadata-location");
+
+    // this will only update the metadata location without writing a new metadata log entry or
+    // updating lastUpdatedMillis
+    TableMetadata newMetadata =
+        TableMetadata.buildFrom(metadata).withMetadataLocation("new-metadata-location").build();
+    assertThat(newMetadata.lastUpdatedMillis()).isEqualTo(metadata.lastUpdatedMillis());
+    assertThat(newMetadata.metadataFileLocation()).isEqualTo("new-metadata-location");
+    assertThat(newMetadata.previousFiles()).isEmpty();
+
+    TableMetadata updatedMetadata =
+        TableMetadata.buildFrom(newMetadata)
+            .withMetadataLocation("updated-metadata-location")
+            .build();
+    assertThat(updatedMetadata.lastUpdatedMillis()).isEqualTo(newMetadata.lastUpdatedMillis());
+    assertThat(updatedMetadata.metadataFileLocation()).isEqualTo("updated-metadata-location");
+    assertThat(updatedMetadata.previousFiles()).isEmpty();
+  }
 }