Test explaining sort | stats avg

Signed-off-by: Yuanchun Shen <yuanchu@amazon.com>

Author: yuancu

integ-test/src/test/java/org/opensearch/sql/ppl/ExplainIT.java

@@ -125,6 +125,23 @@ public void testMultiSortPushDownExplain() throws IOException {
                 + "| fields account_number, firstname, address, balance, gender"));
   }
 
+  @Test
+  public void testSortThenAggregatePushDownExplain() throws IOException {
+    // TODO: Remove pushed-down sort in DSL in expectedOutput/ppl/explain_sort_then_agg_push.json
+    //  existing collations should be eliminated when pushing down aggregations
+    String expected =
+        isCalciteEnabled()
+            ? loadFromFile("expectedOutput/calcite/explain_sort_then_agg_push.json")
+            : loadFromFile("expectedOutput/ppl/explain_sort_then_agg_push.json");
+
+    assertJsonEqualsIgnoreId(
+        expected,
+        explainQueryToString(
+            "source=opensearch-sql_test_index_account"
+                + "| sort balance, age "
+                + "| stats avg(balance) by state"));
+  }
+
   @Test
   public void testLimitPushDownExplain() throws IOException {
     String expected =

integ-test/src/test/resources/expectedOutput/calcite/explain_sort_then_agg_push.json

@@ -0,0 +1,6 @@
+{
+  "calcite": {
+    "logical": "LogicalProject(avg(balance)=[$1], state=[$0])\n  LogicalAggregate(group=[{0}], avg(balance)=[AVG($1)])\n    LogicalProject(state=[$7], balance=[$3])\n      LogicalSort(sort0=[$3], sort1=[$8], dir0=[ASC], dir1=[ASC])\n        CalciteLogicalIndexScan(table=[[OpenSearch, opensearch-sql_test_index_account]])\n",
+    "physical": "EnumerableCalc(expr#0..1=[{inputs}], avg(balance)=[$t1], state=[$t0])\n  CalciteEnumerableIndexScan(table=[[OpenSearch, opensearch-sql_test_index_account]], PushDownContext=[[PROJECT->[balance, state, age], AGGREGATION->rel#1428:LogicalAggregate.NONE.[](input=RelSubset#1418,group={1},avg(balance)=AVG($0))], OpenSearchRequestBuilder(sourceBuilder={\"from\":0,\"size\":0,\"timeout\":\"1m\",\"_source\":{\"includes\":[\"balance\",\"state\",\"age\"],\"excludes\":[]},\"aggregations\":{\"composite_buckets\":{\"composite\":{\"size\":1000,\"sources\":[{\"state\":{\"terms\":{\"field\":\"state.keyword\",\"missing_bucket\":true,\"missing_order\":\"first\",\"order\":\"asc\"}}}]},\"aggregations\":{\"avg(balance)\":{\"avg\":{\"field\":\"balance\"}}}}}}, requestedTotalSize=2147483647, pageSize=null, startFrom=0)])\n"
+  }
+}

integ-test/src/test/resources/expectedOutput/ppl/explain_sort_then_agg_push.json

@@ -0,0 +1,17 @@
+{
+  "root": {
+    "name": "ProjectOperator",
+    "description": {
+      "fields": "[avg(balance), state]"
+    },
+    "children": [
+      {
+        "name": "OpenSearchIndexScan",
+        "description": {
+          "request": "OpenSearchQueryRequest(indexName=opensearch-sql_test_index_account, sourceBuilder={\"from\":0,\"size\":0,\"timeout\":\"1m\",\"sort\":[{\"balance\":{\"order\":\"asc\",\"missing\":\"_first\"}},{\"age\":{\"order\":\"asc\",\"missing\":\"_first\"}}],\"aggregations\":{\"composite_buckets\":{\"composite\":{\"size\":1000,\"sources\":[{\"state\":{\"terms\":{\"field\":\"state.keyword\",\"missing_bucket\":true,\"missing_order\":\"first\",\"order\":\"asc\"}}}]},\"aggregations\":{\"avg(balance)\":{\"avg\":{\"field\":\"balance\"}}}}}}, needClean=true, searchDone=false, pitId=null, cursorKeepAlive=null, searchAfter=null, searchResponse=null)"
+        },
+        "children": []
+      }
+    ]
+  }
+}