Simplify EsqlExecution info serialization

server/src/main/java/org/elasticsearch/common/io/stream/StreamInput.java

@@ -802,6 +802,28 @@ public <K, V> Map<K, V> readMapValues(final Writeable.Reader<V> valueReader, fin
         return map;
     }
 
+    /**
+     * Reads a multiple {@code V}-values and then converts them to a {@code Map} using keyMapper.
+     *
+     * @param valueReader The value reader
+     * @param keyMapper function to create a key from a value
+     * @param constructor map constructor
+     * @return Never {@code null}.
+     */
+    public <K, V, M extends Map<K, V>> M readMapValues(
+        final Writeable.Reader<V> valueReader,
+        final Function<V, K> keyMapper,
+        final IntFunction<M> constructor
+    ) throws IOException {
+        final int size = readArraySize();
+        final M map = constructor.apply(size);
+        for (int i = 0; i < size; i++) {
+            V value = valueReader.read(this);
+            map.put(keyMapper.apply(value), value);
+        }
+        return map;
+    }
+
     /**
      * If the returned map contains any entries it will be mutable. If it is empty it might be immutable.
      */

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/action/EsqlExecutionInfo.java

@@ -13,7 +13,6 @@
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.io.stream.Writeable;
-import org.elasticsearch.common.util.concurrent.ConcurrentCollections;
 import org.elasticsearch.common.xcontent.ChunkedToXContentHelper;
 import org.elasticsearch.common.xcontent.ChunkedToXContentObject;
 import org.elasticsearch.core.Predicates;
@@ -37,6 +36,7 @@
 import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 import java.util.function.BiFunction;
 import java.util.function.Predicate;
@@ -66,7 +66,7 @@ public class EsqlExecutionInfo implements ChunkedToXContentObject, Writeable {
     // The Map itself is immutable after construction - all Clusters will be accounted for at the start of the search.
     // Updates to the Cluster occur with the updateCluster method that given the key to map transforms an
     // old Cluster Object to a new Cluster Object with the remapping function.
-    public final Map<String, Cluster> clusterInfo;
+    public final ConcurrentMap<String, Cluster> clusterInfo;
     // whether the user has asked for CCS metadata to be in the JSON response (the overall took will always be present)
     private final boolean includeCCSMetadata;
 
@@ -90,7 +90,7 @@ public EsqlExecutionInfo(boolean includeCCSMetadata) {
      * @param includeCCSMetadata (user defined setting) whether to include the CCS metadata in the HTTP response
      */
     public EsqlExecutionInfo(Predicate<String> skipUnavailablePredicate, boolean includeCCSMetadata) {
-        this.clusterInfo = ConcurrentCollections.newConcurrentMap();
+        this.clusterInfo = new ConcurrentHashMap<>();
         this.skipUnavailablePredicate = skipUnavailablePredicate;
         this.includeCCSMetadata = includeCCSMetadata;
         this.relativeStart = TimeSpan.start();
@@ -108,26 +108,9 @@ public EsqlExecutionInfo(Predicate<String> skipUnavailablePredicate, boolean inc
 
     public EsqlExecutionInfo(StreamInput in) throws IOException {
         this.overallTook = in.readOptionalTimeValue();
-        List<EsqlExecutionInfo.Cluster> clusterList = in.readCollectionAsList(EsqlExecutionInfo.Cluster::new);
-        if (clusterList.isEmpty()) {
-            this.clusterInfo = ConcurrentCollections.newConcurrentMap();
-        } else {
-            Map<String, EsqlExecutionInfo.Cluster> m = ConcurrentCollections.newConcurrentMap();
-            clusterList.forEach(c -> m.put(c.getClusterAlias(), c));
-            this.clusterInfo = m;
-        }
-        if (in.getTransportVersion().onOrAfter(TransportVersions.V_8_16_0)) {
-            this.includeCCSMetadata = in.readBoolean();
-        } else {
-            this.includeCCSMetadata = false;
-        }
-
-        if (in.getTransportVersion().onOrAfter(TransportVersions.ESQL_RESPONSE_PARTIAL)) {
-            this.isPartial = in.readBoolean();
-        } else {
-            this.isPartial = false;
-        }
-
+        this.clusterInfo = in.readMapValues(EsqlExecutionInfo.Cluster::new, Cluster::getClusterAlias, ConcurrentHashMap::new);
+        this.includeCCSMetadata = in.getTransportVersion().onOrAfter(TransportVersions.V_8_16_0) ? in.readBoolean() : false;
+        this.isPartial = in.getTransportVersion().onOrAfter(TransportVersions.ESQL_RESPONSE_PARTIAL) ? in.readBoolean() : false;
         this.skipUnavailablePredicate = Predicates.always();
         this.relativeStart = null;
         if (in.getTransportVersion().onOrAfter(TransportVersions.ESQL_QUERY_PLANNING_DURATION)
@@ -141,7 +124,7 @@ public EsqlExecutionInfo(StreamInput in) throws IOException {
     public void writeTo(StreamOutput out) throws IOException {
         out.writeOptionalTimeValue(overallTook);
         if (clusterInfo != null) {
-            out.writeCollection(clusterInfo.values().stream().toList());
+            out.writeCollection(clusterInfo.values());
         } else {
             out.writeCollection(Collections.emptyList());
         }