perf: optimize critical path for executeQuery

google-cloud-spanner/src/main/java/com/google/cloud/spanner/AbstractReadContext.java

@@ -580,19 +580,17 @@ private ResultSet executeQueryInternal(
   @VisibleForTesting
   QueryOptions buildQueryOptions(QueryOptions requestOptions) {
     // Shortcut for the most common return value.
-    if (defaultQueryOptions.equals(QueryOptions.getDefaultInstance()) && requestOptions == null) {
-      return QueryOptions.getDefaultInstance();
+    if (requestOptions == null) {
+      return defaultQueryOptions;
     }
-    // Create a builder based on the default query options.
-    QueryOptions.Builder builder = defaultQueryOptions.toBuilder();
-    // Then overwrite with specific options for this query.
-    if (requestOptions != null) {
-      builder.mergeFrom(requestOptions);
-    }
-    return builder.build();
+    return defaultQueryOptions.toBuilder().mergeFrom(requestOptions).build();
   }
 
   RequestOptions buildRequestOptions(Options options) {
+    if (!(options.hasPriority() || options.hasTag() || getTransactionTag() != null)) {
+      return RequestOptions.getDefaultInstance();
+    }
+
     RequestOptions.Builder builder = RequestOptions.newBuilder();
     if (options.hasPriority()) {
       builder.setPriority(options.priority());

google-cloud-spanner/src/main/java/com/google/cloud/spanner/AbstractResultSet.java

@@ -1090,7 +1090,7 @@ abstract static class ResumableStreamIterator extends AbstractIterator<PartialRe
     private final RetrySettings streamingRetrySettings;
     private final Set<Code> retryableCodes;
     private static final Logger logger = Logger.getLogger(ResumableStreamIterator.class.getName());
-    private final BackOff backOff;
+    private BackOff backOff;
     private final LinkedList<PartialResultSet> buffer = new LinkedList<>();
     private final int maxBufferSize;
     private final Span span;
@@ -1115,7 +1115,6 @@ protected ResumableStreamIterator(
       this.span = tracer.spanBuilderWithExplicitParent(streamName, parent).startSpan();
       this.streamingRetrySettings = Preconditions.checkNotNull(streamingRetrySettings);
       this.retryableCodes = Preconditions.checkNotNull(retryableCodes);
-      this.backOff = newBackOff();
     }
 
     private ExponentialBackOff newBackOff() {
@@ -1289,6 +1288,9 @@ protected PartialResultSet computeNext() {
               if (delay != -1) {
                 backoffSleep(context, delay);
               } else {
+                if (backOff == null) {
+                  backOff = newBackOff();
+                }
                 backoffSleep(context, backOff);
               }
             }

google-cloud-spanner/src/main/java/com/google/cloud/spanner/ForwardingResultSet.java

@@ -17,10 +17,10 @@
 package com.google.cloud.spanner;
 
 import com.google.common.base.Preconditions;
-import com.google.common.base.Supplier;
 import com.google.common.base.Suppliers;
 import com.google.spanner.v1.ResultSetMetadata;
 import com.google.spanner.v1.ResultSetStats;
+import java.util.function.Supplier;
 
 /** Forwarding implementation of ResultSet that forwards all calls to a delegate. */
 public class ForwardingResultSet extends ForwardingStructReader implements ResultSet {

google-cloud-spanner/src/main/java/com/google/cloud/spanner/ForwardingStructReader.java

@@ -20,10 +20,10 @@
 import com.google.cloud.Date;
 import com.google.cloud.Timestamp;
 import com.google.common.base.Preconditions;
-import com.google.common.base.Supplier;
 import com.google.common.base.Suppliers;
 import java.math.BigDecimal;
 import java.util.List;
+import java.util.function.Supplier;
 
 /** Forwarding implements of StructReader */
 public class ForwardingStructReader implements StructReader {

google-cloud-spanner/src/main/java/com/google/cloud/spanner/SessionImpl.java

@@ -99,7 +99,7 @@ interface SessionTransaction {
   ByteString readyTransactionId;
   private final Map<SpannerRpc.Option, ?> options;
   private Span currentSpan;
-  private volatile Instant lastUseTime;
+  private Instant lastUseTime;
 
   SessionImpl(SpannerImpl spanner, String name, Map<SpannerRpc.Option, ?> options) {
     this.spanner = spanner;