Fix format problem in composite of unmapped (#50869)

When a composite aggregation is reduced using the results from an
index that has one of the fields unmapped we were throwing away the
formatter. This is mildly annoying, except in the case of IP addresses
which were coming out as non-utf-8-characters. And tripping assertions.

This carefully preserves the formatter from the working bucket.

Closes #50600

rest-api-spec/src/main/resources/rest-api-spec/test/search.aggregation/230_composite.yml

@@ -694,6 +694,7 @@ setup:
   - match: { aggregations.test.buckets.3.key.geo: "12/2048/0" }
   - match: { aggregations.test.buckets.3.key.kw: "bar" }
   - match: { aggregations.test.buckets.3.doc_count: 1 }
+
 ---
 "Simple Composite aggregation with geotile grid add aggregate after":
   - skip:
@@ -735,3 +736,49 @@ setup:
   - match: { aggregations.test.buckets.2.key.geo: "12/2048/0" }
   - match: { aggregations.test.buckets.2.key.kw: "bar" }
   - match: { aggregations.test.buckets.2.doc_count: 1 }
+
+---
+"Mixed ip and unmapped fields":
+  - skip:
+      version: " - 7.99.99"
+      reason: This will fail against 7.x until the fix is backported there
+  # It is important that the index *without* the ip field be sorted *before*
+  # the index *with* the ip field because that has caused bugs in the past.
+  - do:
+      indices.create:
+        index: test_1
+  - do:
+      indices.create:
+        index: test_2
+        body:
+          mappings:
+            properties:
+              f:
+                type: ip
+  - do:
+      index:
+        index:   test_2
+        id:      1
+        body:    { "f": "192.168.0.1" }
+        refresh: true
+
+  - do:
+      search:
+        index: test_*
+        body:
+          aggregations:
+            test:
+              composite:
+                sources: [
+                  "f": {
+                    "terms": {
+                      "field": "f"
+                    }
+                  }
+                ]
+
+  - match: { hits.total.value: 1 }
+  - match: { hits.total.relation: eq }
+  - length: { aggregations.test.buckets: 1 }
+  - match: { aggregations.test.buckets.0.key.f: "192.168.0.1" }
+  - match: { aggregations.test.buckets.0.doc_count: 1 }

server/src/main/java/org/elasticsearch/search/DocValueFormat.java

@@ -139,6 +139,11 @@ public double parseDouble(String value, boolean roundUp, LongSupplier now) {
         public BytesRef parseBytesRef(String value) {
             return new BytesRef(value);
         }
+
+        @Override
+        public String toString() {
+            return "raw";
+        }
     };
 
     DocValueFormat BINARY = new DocValueFormat() {
@@ -335,6 +340,11 @@ public String format(BytesRef value) {
         public BytesRef parseBytesRef(String value) {
             return new BytesRef(InetAddressPoint.encode(InetAddresses.forString(value)));
         }
+
+        @Override
+        public String toString() {
+            return "ip";
+        }
     };
 
     final class Decimal implements DocValueFormat {

server/src/main/java/org/elasticsearch/search/aggregations/bucket/composite/InternalComposite.java

@@ -134,6 +134,13 @@ public List<InternalBucket> getBuckets() {
         return buckets;
     }
 
+    /**
+     * The formats used when writing the keys. Package private for testing.
+     */
+    List<DocValueFormat> getFormats() {
+        return formats;
+    }
+
     @Override
     public Map<String, Object> afterKey() {
         if (afterKey != null) {
@@ -189,8 +196,17 @@ public InternalAggregation reduce(List<InternalAggregation> aggregations, Reduce
             reduceContext.consumeBucketsAndMaybeBreak(1);
             result.add(reduceBucket);
         }
-        final CompositeKey lastKey = result.size() > 0 ? result.get(result.size()-1).getRawKey() : null;
-        return new InternalComposite(name, size, sourceNames, formats, result, lastKey, reverseMuls,
+
+        List<DocValueFormat> reducedFormats = formats;
+        CompositeKey lastKey = null;
+        if (result.size() > 0) {
+            lastBucket = result.get(result.size() - 1);
+            /* Attach the formats from the last bucket to the reduced composite
+             * so that we can properly format the after key. */
+            reducedFormats = lastBucket.formats;
+            lastKey = lastBucket.getRawKey();
+        }
+        return new InternalComposite(name, size, sourceNames, reducedFormats, result, lastKey, reverseMuls,
             earlyTerminated, pipelineAggregators(), metaData);
     }
 
@@ -204,7 +220,12 @@ protected InternalBucket reduceBucket(List<InternalBucket> buckets, ReduceContex
             aggregations.add(bucket.aggregations);
         }
         InternalAggregations aggs = InternalAggregations.reduce(aggregations, context);
-        return new InternalBucket(sourceNames, formats, buckets.get(0).key, reverseMuls, docCount, aggs);
+        /* Use the formats from the bucket because they'll be right to format
+         * the key. The formats on the InternalComposite doing the reducing are
+         * just whatever formats make sense for *its* index. This can be real
+         * trouble when the index doing the reducing is unmapped. */
+        var reducedFormats = buckets.get(0).formats;
+        return new InternalBucket(sourceNames, reducedFormats, buckets.get(0).key, reverseMuls, docCount, aggs);
     }
 
     @Override
@@ -334,6 +355,13 @@ public Aggregations getAggregations() {
             return aggregations;
         }
 
+        /**
+         * The formats used when writing the keys. Package private for testing.
+         */
+        List<DocValueFormat> getFormats() {
+            return formats;
+        }
+
         @Override
         public int compareKey(InternalBucket other) {
             for (int i = 0; i < key.size(); i++) {

server/src/test/java/org/elasticsearch/search/aggregations/bucket/composite/InternalCompositeTests.java

@@ -47,6 +47,9 @@
 import java.util.stream.IntStream;
 
 import static com.carrotsearch.randomizedtesting.RandomizedTest.randomAsciiLettersOfLengthBetween;
+import static java.util.Collections.emptyList;
+import static java.util.Collections.emptyMap;
+import static java.util.stream.Collectors.toList;
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.greaterThan;
@@ -238,8 +241,7 @@ public void testReduceSame() throws IOException {
         for (int i = 0; i < numSame; i++) {
             toReduce.add(result);
         }
-        InternalComposite finalReduce = (InternalComposite) result.reduce(toReduce,
-            new InternalAggregation.ReduceContext(BigArrays.NON_RECYCLING_INSTANCE, null, true));
+        InternalComposite finalReduce = (InternalComposite) result.reduce(toReduce, reduceContext());
         assertThat(finalReduce.getBuckets().size(), equalTo(result.getBuckets().size()));
         Iterator<InternalComposite.InternalBucket> expectedIt = result.getBuckets().iterator();
         for (InternalComposite.InternalBucket bucket : finalReduce.getBuckets()) {
@@ -249,6 +251,30 @@ public void testReduceSame() throws IOException {
         }
     }
 
+    /**
+     * Check that reducing with an unmapped index produces useful formats.
+     */
+    public void testReduceUnmapped() throws IOException {
+        var mapped = createTestInstance(randomAlphaOfLength(10), emptyList(), emptyMap(), InternalAggregations.EMPTY);
+        var rawFormats = formats.stream().map(f -> DocValueFormat.RAW).collect(toList());
+        var unmapped = new InternalComposite(mapped.getName(), mapped.getSize(), sourceNames,
+                rawFormats, emptyList(), null, reverseMuls, true, emptyList(), emptyMap());
+        List<InternalAggregation> toReduce = Arrays.asList(unmapped, mapped);
+        Collections.shuffle(toReduce, random());
+        InternalComposite finalReduce = (InternalComposite) unmapped.reduce(toReduce, reduceContext());
+        assertThat(finalReduce.getBuckets().size(), equalTo(mapped.getBuckets().size()));
+        if (false == mapped.getBuckets().isEmpty()) {
+            assertThat(finalReduce.getFormats(), equalTo(mapped.getFormats()));
+        }
+        var expectedIt = mapped.getBuckets().iterator();
+        for (var bucket : finalReduce.getBuckets()) {
+            InternalComposite.InternalBucket expectedBucket = expectedIt.next();
+            assertThat(bucket.getRawKey(), equalTo(expectedBucket.getRawKey()));
+            assertThat(bucket.getDocCount(), equalTo(expectedBucket.getDocCount()));
+            assertThat(bucket.getFormats(), equalTo(expectedBucket.getFormats()));
+        }
+    }
+
     public void testCompareCompositeKeyBiggerFieldName() {
         InternalComposite.ArrayMap key1 = createMap(
             Arrays.asList("field1", "field2"),
@@ -381,4 +407,8 @@ private InternalComposite.ArrayMap createMap(List<String> fields, Comparable[] v
             values
         );
     }
+
+    private InternalAggregation.ReduceContext reduceContext() {
+        return new InternalAggregation.ReduceContext(BigArrays.NON_RECYCLING_INSTANCE, null, true);
+    }
 }