[Transform] add support for "missing" aggregation (#63651)

add support for the missing (bucket) aggregation (counts docs with a configured missing field value)
in transform. The output is mapped to name:count, the mapping type is long.

docs/reference/rest-api/common-parms.asciidoc

@@ -660,6 +660,7 @@ supported:
 * <<search-aggregations-metrics-geocentroid-aggregation,Geo centroid>>
 * <<search-aggregations-metrics-max-aggregation,Max>>
 * <<search-aggregations-metrics-min-aggregation,Min>>
+* <<search-aggregations-bucket-missing-aggregation,Missing>>
 * <<search-aggregations-metrics-percentile-aggregation,Percentiles>>
 * <<search-aggregations-bucket-rare-terms-aggregation, Rare Terms>>
 * <<search-aggregations-metrics-scripted-metric-aggregation,Scripted metric>>

x-pack/plugin/transform/qa/single-node-tests/src/javaRestTest/java/org/elasticsearch/xpack/transform/integration/TransformPivotRestIT.java

@@ -87,10 +87,13 @@ public class TransformPivotRestIT extends TransformRestTestCase {
 
         // get and check some users
         assertOnePivotValue(transformIndex + "/_search?q=reviewer:user_0", 3.776978417);
+        assertOneCount(transformIndex + "/_search?q=reviewer:user_0", "hits.hits._source.affiliate_missing", 0);
         assertOnePivotValue(transformIndex + "/_search?q=reviewer:user_5", 3.72);
+        assertOneCount(transformIndex + "/_search?q=reviewer:user_5", "hits.hits._source.affiliate_missing", 25);
         assertOnePivotValue(transformIndex + "/_search?q=reviewer:user_11", 3.846153846);
         assertOnePivotValue(transformIndex + "/_search?q=reviewer:user_20", 3.769230769);
         assertOnePivotValue(transformIndex + "/_search?q=reviewer:user_26", 3.918918918);
+        assertOneCount(transformIndex + "/_search?q=reviewer:user_26", "hits.hits._source.affiliate_missing", 0);
     }
 
     public void testSimpleDataStreamPivot() throws Exception {

x-pack/plugin/transform/qa/single-node-tests/src/javaRestTest/java/org/elasticsearch/xpack/transform/integration/TransformRestTestCase.java

@@ -101,6 +101,8 @@ public abstract class TransformRestTestCase extends ESRestTestCase {
             long user = Math.round(Math.pow(i * 31 % 1000, distributionTable[i % distributionTable.length]) % 27);
             int stars = distributionTable[(i * 33) % distributionTable.length];
             long business = Math.round(Math.pow(user * stars, distributionTable[i % distributionTable.length]) % 13);
+            long affiliate = Math.round(Math.pow(user * stars, distributionTable[i % distributionTable.length]) % 11);
+
             if (i % 12 == 0) {
                 hour = 10 + (i % 13);
             }
@@ -133,6 +135,9 @@ public abstract class TransformRestTestCase extends ESRestTestCase {
             if ((user == userWithMissingBuckets && missingBucketField.equals("timestamp")) == false) {
                 bulk.append("\"timestamp\":\"").append(date_string).append("\",");
             }
+            if ((user == userWithMissingBuckets && missingBucketField.equals("affiliate_id")) == false) {
+                bulk.append("\"affiliate_id\":\"").append("affiliate_").append(affiliate).append("\",");
+            }
 
             // always add @timestamp to avoid complicated logic regarding ','
             bulk.append("\"@timestamp\":\"").append(date_string).append("\"");
@@ -185,6 +190,9 @@ public abstract class TransformRestTestCase extends ESRestTestCase {
                     .startObject("location")
                     .field("type", "geo_point")
                     .endObject()
+                    .startObject("affiliate_id")
+                    .field("type", "keyword")
+                    .endObject()
                     .endObject()
                     .endObject();
             }
@@ -221,7 +229,7 @@ public abstract class TransformRestTestCase extends ESRestTestCase {
     }
 
     protected void createReviewsIndex(String indexName) throws IOException {
-        createReviewsIndex(indexName, 1000, "date", false, -1, null);
+        createReviewsIndex(indexName, 1000, "date", false, 5, "affiliate_id");
     }
 
     protected void createPivotReviewsTransform(String transformId, String transformIndex, String query) throws IOException {
@@ -298,6 +306,11 @@ public abstract class TransformRestTestCase extends ESRestTestCase {
             + "     \"avg_rating\": {"
             + "       \"avg\": {"
             + "         \"field\": \"stars\""
+            + " } },"
+            + "     \"affiliate_missing\": {"
+            + "       \"missing\": {"
+            + "         \"field\": \"affiliate_id\""
+
             + " } } } },"
             + "\"frequency\":\"1s\""
             + "}";
@@ -480,8 +493,13 @@ public abstract class TransformRestTestCase extends ESRestTestCase {
 
         // the configuration index should be empty
         Request request = new Request("GET", TransformInternalIndexConstants.LATEST_INDEX_NAME + "/_search");
-        request.setOptions(expectWarnings("this request accesses system indices: [" + TransformInternalIndexConstants.LATEST_INDEX_NAME +
-            "], but in a future major version, direct access to system indices will be prevented by default"));
+        request.setOptions(
+            expectWarnings(
+                "this request accesses system indices: ["
+                    + TransformInternalIndexConstants.LATEST_INDEX_NAME
+                    + "], but in a future major version, direct access to system indices will be prevented by default"
+            )
+        );
         try {
             Response searchResponse = adminClient().performRequest(request);
             Map<String, Object> searchResult = entityAsMap(searchResponse);
@@ -541,6 +559,14 @@ public abstract class TransformRestTestCase extends ESRestTestCase {
         assertEquals(expected, actual, 0.000001);
     }
 
+    protected void assertOneCount(String query, String field, int expected) throws IOException {
+        Map<String, Object> searchResult = getAsMap(query);
+
+        assertEquals(1, XContentMapValues.extractValue("hits.total.value", searchResult));
+        int actual = (Integer) ((List<?>) XContentMapValues.extractValue(field, searchResult)).get(0);
+        assertEquals(expected, actual);
+    }
+
     protected static String getTransformEndpoint() {
         return useDeprecatedEndpoints ? TransformField.REST_BASE_PATH_TRANSFORMS_DEPRECATED : TransformField.REST_BASE_PATH_TRANSFORMS;
     }

x-pack/plugin/transform/src/main/java/org/elasticsearch/xpack/transform/transforms/pivot/TransformAggregations.java

@@ -66,7 +66,6 @@ public final class TransformAggregations {
         "ip_range",
         "matrix_stats",
         "median_absolute_deviation",
-        "missing",
         "nested",
         "percentile_ranks",
         "range",
@@ -110,7 +109,8 @@ public final class TransformAggregations {
         PERCENTILES("percentiles", DOUBLE),
         FILTER("filter", LONG),
         TERMS("terms", FLATTENED),
-        RARE_TERMS("rare_terms", FLATTENED);
+        RARE_TERMS("rare_terms", FLATTENED),
+        MISSING("missing", LONG);
 
         private final String aggregationType;
         private final String targetMapping;