EN-51893 | CHORE : Adding Last aggregation operator (#215)

* Adding ast aggregation operator

* added integration tests

* resolved comments

* minor fix

Author: singh-viikram

document-store/src/integrationTest/java/org/hypertrace/core/documentstore/DocStoreQueryV1Test.java

@@ -11,6 +11,7 @@
 import static org.hypertrace.core.documentstore.expression.operators.AggregationOperator.COUNT;
 import static org.hypertrace.core.documentstore.expression.operators.AggregationOperator.DISTINCT_ARRAY;
 import static org.hypertrace.core.documentstore.expression.operators.AggregationOperator.DISTINCT_COUNT;
+import static org.hypertrace.core.documentstore.expression.operators.AggregationOperator.LAST;
 import static org.hypertrace.core.documentstore.expression.operators.AggregationOperator.MAX;
 import static org.hypertrace.core.documentstore.expression.operators.AggregationOperator.MIN;
 import static org.hypertrace.core.documentstore.expression.operators.AggregationOperator.SUM;
@@ -1334,6 +1335,24 @@ public void testQueryV1AggregationFilterWithWhereClause(String dataStoreName) th
         dataStoreName, resultDocs, "query/test_aggr_filter_and_where_filter_result.json", 2);
   }
 
+  @ParameterizedTest
+  @ArgumentsSource(MongoProvider.class)
+  public void testQueryV1LastAggregationOperator(String dataStoreName) throws IOException {
+    Collection collection = getCollection(dataStoreName);
+
+    org.hypertrace.core.documentstore.query.Query query =
+        org.hypertrace.core.documentstore.query.Query.builder()
+            .addSelection(IdentifierExpression.of("item"))
+            .addAggregation(IdentifierExpression.of("item"))
+            .addSelection(
+                AggregateExpression.of(LAST, IdentifierExpression.of("price")), "last_price")
+            .build();
+
+    Iterator<Document> resultDocs = collection.aggregate(query);
+    assertDocsAndSizeEqualWithoutOrder(
+        dataStoreName, resultDocs, "query/test_last_aggregation_operator.json", 4);
+  }
+
   @Nested
   class StartsWithOperatorTest {
 

document-store/src/integrationTest/resources/query/collection_data.json

@@ -6,7 +6,10 @@
     "quantity": 2,
     "date": "2014-03-01T08:00:00Z",
     "props": {
-      "colors": ["Blue", "Green"],
+      "colors": [
+        "Blue",
+        "Green"
+      ],
       "brand": "Dettol",
       "size": "M",
       "seller": {
@@ -70,7 +73,9 @@
     "quantity": 10,
     "date": "2014-03-15T09:00:00Z",
     "props": {
-      "colors": ["Black"],
+      "colors": [
+        "Black"
+      ],
       "brand": "Sunsilk",
       "size": "L",
       "seller": {
@@ -133,7 +138,10 @@
     "quantity": 5,
     "date": "2014-04-04T21:23:13.331Z",
     "props": {
-      "colors": ["Orange", "Blue"],
+      "colors": [
+        "Orange",
+        "Blue"
+      ],
       "brand": "Lifebuoy",
       "size": "S",
       "seller": {
@@ -176,4 +184,4 @@
     "quantity": 5,
     "date": "2016-02-06T20:20:13Z"
   }
-]
+]

document-store/src/integrationTest/resources/query/test_last_aggregation_operator.json

@@ -0,0 +1,18 @@
+[
+  {
+    "item":"Shampoo",
+    "last_price":5
+  },
+  {
+    "item":"Comb",
+    "last_price":7.5
+  },
+  {
+    "item":"Mirror",
+    "last_price":20
+  },
+  {
+    "item":"Soap",
+    "last_price":20
+  }
+]

document-store/src/main/java/org/hypertrace/core/documentstore/expression/operators/AggregationOperator.java

@@ -11,4 +11,5 @@ public enum AggregationOperator {
   SUM,
   MIN,
   MAX,
+  LAST,
 }

document-store/src/main/java/org/hypertrace/core/documentstore/mongo/query/parser/MongoAggregateExpressionParser.java

@@ -5,6 +5,7 @@
 import static org.hypertrace.core.documentstore.expression.operators.AggregationOperator.COUNT;
 import static org.hypertrace.core.documentstore.expression.operators.AggregationOperator.DISTINCT;
 import static org.hypertrace.core.documentstore.expression.operators.AggregationOperator.DISTINCT_ARRAY;
+import static org.hypertrace.core.documentstore.expression.operators.AggregationOperator.LAST;
 import static org.hypertrace.core.documentstore.expression.operators.AggregationOperator.MAX;
 import static org.hypertrace.core.documentstore.expression.operators.AggregationOperator.MIN;
 import static org.hypertrace.core.documentstore.expression.operators.AggregationOperator.SUM;
@@ -30,6 +31,7 @@ final class MongoAggregateExpressionParser extends MongoSelectTypeExpressionPars
               put(MIN, "$min");
               put(MAX, "$max");
               put(COUNT, "$push");
+              put(LAST, "$last");
             }
           });