From 59d1d1a7db11d6952de5b321fde66f7951796c85 Mon Sep 17 00:00:00 2001
From: laughingman7743 <laughingman7743@gmail.com>
Date: Sat, 8 Aug 2026 21:31:37 +0900
Subject: [PATCH] perf(bigtable): build the entry proto once in createResource

MutateRowsBatchingDescriptor.createResource() built the same
MutateRowsRequest.Entry twice for every element added to a bulk-mutation
batcher: once through countBytes() to read the serialized size, and once
directly to read the mutation count. RowMutationEntry.toProto() memoizes
nothing, so the second construction was pure overhead, and BatcherImpl.add()
calls createResource for every accepted element.

Build the proto once and read both values from it. Behaviour-preserving.
Measured, this halves the bytes allocated per element.

MutateRowsBatchingDescriptorTest had no coverage of createResource or
createEmptyResource; both are added.
---
 .../MutateRowsBatchingDescriptor.java         |  5 ++--
 .../MutateRowsBatchingDescriptorTest.java     | 29 +++++++++++++++++++
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/java-bigtable/google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/stub/mutaterows/MutateRowsBatchingDescriptor.java b/java-bigtable/google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/stub/mutaterows/MutateRowsBatchingDescriptor.java
index 87f5c88d3eb1..5ac49f491b9d 100644
--- a/java-bigtable/google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/stub/mutaterows/MutateRowsBatchingDescriptor.java
+++ b/java-bigtable/google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/stub/mutaterows/MutateRowsBatchingDescriptor.java
@@ -20,6 +20,7 @@
 import com.google.api.gax.batching.BatchResource;
 import com.google.api.gax.batching.BatchingDescriptor;
 import com.google.api.gax.batching.BatchingRequestBuilder;
+import com.google.bigtable.v2.MutateRowsRequest;
 import com.google.cloud.bigtable.data.v2.models.BulkMutation;
 import com.google.cloud.bigtable.data.v2.models.MutateRowsException;
 import com.google.cloud.bigtable.data.v2.models.MutateRowsException.FailedMutation;
@@ -101,8 +102,8 @@ public long countBytes(RowMutationEntry entry) {
 
   @Override
   public BatchResource createResource(RowMutationEntry element) {
-    long byteCount = countBytes(element);
-    return MutateRowsBatchResource.create(1, byteCount, element.toProto().getMutationsCount());
+    MutateRowsRequest.Entry proto = element.toProto();
+    return MutateRowsBatchResource.create(1, proto.getSerializedSize(), proto.getMutationsCount());
   }
 
   @Override
diff --git a/java-bigtable/google-cloud-bigtable/src/test/java/com/google/cloud/bigtable/data/v2/stub/mutaterows/MutateRowsBatchingDescriptorTest.java b/java-bigtable/google-cloud-bigtable/src/test/java/com/google/cloud/bigtable/data/v2/stub/mutaterows/MutateRowsBatchingDescriptorTest.java
index 11658d8792bd..a3115fab7a5b 100644
--- a/java-bigtable/google-cloud-bigtable/src/test/java/com/google/cloud/bigtable/data/v2/stub/mutaterows/MutateRowsBatchingDescriptorTest.java
+++ b/java-bigtable/google-cloud-bigtable/src/test/java/com/google/cloud/bigtable/data/v2/stub/mutaterows/MutateRowsBatchingDescriptorTest.java
@@ -27,6 +27,7 @@
 import com.google.api.gax.rpc.DeadlineExceededException;
 import com.google.api.gax.rpc.InternalException;
 import com.google.api.gax.rpc.UnavailableException;
+import com.google.bigtable.v2.MutateRowsRequest;
 import com.google.cloud.bigtable.data.v2.internal.RequestContext;
 import com.google.cloud.bigtable.data.v2.models.BulkMutation;
 import com.google.cloud.bigtable.data.v2.models.MutateRowsException;
@@ -64,6 +65,34 @@ public void countBytesTest() {
     assertThat(underTest.countBytes(request)).isEqualTo(bytes);
   }
 
+  @Test
+  public void createResourceTest() {
+    RowMutationEntry request =
+        RowMutationEntry.create(ROW_KEY)
+            .setCell(FAMILY, QUALIFIER, VALUE)
+            .setCell(FAMILY, QUALIFIER, "another-value")
+            .deleteFamily(FAMILY);
+    MutateRowsRequest.Entry proto = request.toProto();
+
+    MutateRowsBatchingDescriptor underTest = new MutateRowsBatchingDescriptor();
+    BatchResource resource = underTest.createResource(request);
+
+    assertThat(resource.getElementCount()).isEqualTo(1);
+    assertThat(resource.getByteCount()).isEqualTo(proto.getSerializedSize());
+    assertThat(((MutateRowsBatchResource) resource).getMutationCount())
+        .isEqualTo(proto.getMutationsCount());
+  }
+
+  @Test
+  public void createEmptyResourceTest() {
+    MutateRowsBatchingDescriptor underTest = new MutateRowsBatchingDescriptor();
+    BatchResource resource = underTest.createEmptyResource();
+
+    assertThat(resource.getElementCount()).isEqualTo(0);
+    assertThat(resource.getByteCount()).isEqualTo(0);
+    assertThat(((MutateRowsBatchResource) resource).getMutationCount()).isEqualTo(0);
+  }
+
   @Test
   public void requestBuilderTest() {
     MutateRowsBatchingDescriptor underTest = new MutateRowsBatchingDescriptor();