[Transform] log search payload for preview (#110653)

A quick change to help debug search requests performed by the validate
and preview API.

Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>

x-pack/plugin/transform/src/main/java/org/elasticsearch/xpack/transform/transforms/common/AbstractCompositeAggFunction.java

@@ -7,6 +7,8 @@
 
 package org.elasticsearch.xpack.transform.transforms.common;
 
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
 import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.ElasticsearchStatusException;
 import org.elasticsearch.action.ActionListener;
@@ -45,6 +47,7 @@ import static org.elasticsearch.core.Strings.format;
  * Basic abstract class for implementing a transform function that utilizes composite aggregations
  */
 public abstract class AbstractCompositeAggFunction implements Function {
+    private static final Logger logger = LogManager.getLogger(AbstractCompositeAggFunction.class);
 
     public static final int TEST_QUERY_PAGE_SIZE = 50;
     public static final String COMPOSITE_AGGREGATION_NAME = "_transform";
@@ -78,7 +81,7 @@ public abstract class AbstractCompositeAggFunction implements Function {
             ClientHelper.TRANSFORM_ORIGIN,
             client,
             TransportSearchAction.TYPE,
-            buildSearchRequest(sourceConfig, timeout, numberOfBuckets),
+            buildSearchRequestForValidation("preview", sourceConfig, timeout, numberOfBuckets),
             ActionListener.wrap(r -> {
                 try {
                     final InternalAggregations aggregations = r.getAggregations();
@@ -116,7 +119,7 @@ public abstract class AbstractCompositeAggFunction implements Function {
         TimeValue timeout,
         ActionListener<Boolean> listener
     ) {
-        SearchRequest searchRequest = buildSearchRequest(sourceConfig, timeout, TEST_QUERY_PAGE_SIZE);
+        SearchRequest searchRequest = buildSearchRequestForValidation("validate", sourceConfig, timeout, TEST_QUERY_PAGE_SIZE);
         ClientHelper.executeWithHeadersAsync(
             headers,
             ClientHelper.TRANSFORM_ORIGIN,
@@ -193,11 +196,12 @@ public abstract class AbstractCompositeAggFunction implements Function {
         TransformProgress progress
     );
 
-    private SearchRequest buildSearchRequest(SourceConfig sourceConfig, TimeValue timeout, int pageSize) {
+    private SearchRequest buildSearchRequestForValidation(String logId, SourceConfig sourceConfig, TimeValue timeout, int pageSize) {
         SearchSourceBuilder sourceBuilder = new SearchSourceBuilder().query(sourceConfig.getQueryConfig().getQuery())
             .runtimeMappings(sourceConfig.getRuntimeMappings())
             .timeout(timeout);
         buildSearchQuery(sourceBuilder, null, pageSize);
+        logger.debug("[{}] Querying {} for data: {}", logId, sourceConfig.getIndex(), sourceBuilder);
         return new SearchRequest(sourceConfig.getIndex()).source(sourceBuilder).indicesOptions(IndicesOptions.LENIENT_EXPAND_OPEN);
     }