Fix sub-fields accessing of generated structs

core/src/main/java/org/opensearch/sql/ast/expression/QualifiedName.java

@@ -22,6 +22,7 @@
 @Getter
 @EqualsAndHashCode(callSuper = false)
 public class QualifiedName extends UnresolvedExpression {
+  public static final String DELIMITER = ".";
   private final List<String> parts;
 
   public QualifiedName(String name) {
@@ -94,7 +95,7 @@ public QualifiedName rest() {
   }
 
   public String toString() {
-    return String.join(".", this.parts);
+    return String.join(DELIMITER, this.parts);
   }
 
   @Override

core/src/main/java/org/opensearch/sql/calcite/QualifiedNameResolver.java

@@ -249,8 +249,10 @@ private static RexNode resolveFieldAccess(
     if (length == parts.size() - start) {
       return field;
     } else {
-      String itemName = joinParts(parts, length + start, parts.size() - 1 - length);
-      return createItemAccess(field, itemName, context);
+      String itemName = joinParts(parts, length + start, parts.size() - length);
+      return context.relBuilder.alias(
+          createItemAccess(field, itemName, context),
+          String.join(QualifiedName.DELIMITER, parts.subList(start, parts.size())));
     }
   }
 

integ-test/src/test/java/org/opensearch/sql/calcite/remote/CalciteExplainIT.java

@@ -38,6 +38,7 @@ public void init() throws Exception {
     loadIndex(Index.LOGS);
     loadIndex(Index.WORKER);
     loadIndex(Index.WORK_INFORMATION);
+    loadIndex(Index.WEBLOG);
   }
 
   @Override
@@ -1416,4 +1417,16 @@ public void testTopKThenSortExplain() throws IOException {
                 + "| sort age "
                 + "| fields age"));
   }
+
+  @Test
+  public void testInternalItemAccessOnStructs() throws IOException {
+    String expected = loadExpectedPlan("access_struct_subfield_with_item.yaml");
+    assertYamlEqualsIgnoreId(
+        expected,
+        explainQueryYaml(
+            String.format(
+                "source=%s | eval info = geoip('dummy-datasource', host) | fields host, info,"
+                    + " info.dummy_sub_field",
+                TEST_INDEX_WEBLOGS)));
+  }
 }

integ-test/src/test/java/org/opensearch/sql/calcite/remote/CalciteGeoIpFunctionsIT.java

@@ -53,4 +53,23 @@ public void testGeoIpEnrichmentWithIpFieldAsInput() throws IOException {
         rows("10.0.0.1", Map.of("country", "USA")),
         rows("fd12:2345:6789:1:a1b2:c3d4:e5f6:789a", Map.of("country", "India")));
   }
+
+  @Test
+  public void testGeoIpEnrichmentAccessingSubField() throws IOException {
+    JSONObject result =
+        executeQuery(
+            String.format(
+                "source=%s | where method='POST' | eval info = geoip('%s', host) | fields host,"
+                    + " info, info.country",
+                TEST_INDEX_WEBLOGS, DATASOURCE_NAME));
+    verifySchema(
+        result, schema("host", "ip"), schema("info", "struct"), schema("info.country", "string"));
+    verifyDataRows(
+        result,
+        rows("10.0.0.1", Map.of("country", "USA", "city", "Seattle"), "USA"),
+        rows(
+            "fd12:2345:6789:1:a1b2:c3d4:e5f6:789a",
+            Map.of("country", "India", "city", "Bengaluru"),
+            "India"));
+  }
 }

integ-test/src/test/resources/expectedOutput/calcite/access_struct_subfield_with_item.yaml

@@ -0,0 +1,8 @@
+calcite:
+  logical: |
+    LogicalSystemLimit(fetch=[10000], type=[QUERY_SIZE_LIMIT])
+      LogicalProject(host=[$0], info=[GEOIP('dummy-datasource':VARCHAR, $0)], info.dummy_sub_field=[ITEM(GEOIP('dummy-datasource':VARCHAR, $0), 'dummy_sub_field')])
+        CalciteLogicalIndexScan(table=[[OpenSearch, opensearch-sql_test_index_weblogs]])
+  physical: |
+    EnumerableCalc(expr#0=[{inputs}], expr#1=['dummy-datasource':VARCHAR], expr#2=[GEOIP($t1, $t0)], expr#3=['dummy_sub_field'], expr#4=[ITEM($t2, $t3)], host=[$t0], $f1=[$t2], $f2=[$t4])
+      CalciteEnumerableIndexScan(table=[[OpenSearch, opensearch-sql_test_index_weblogs]], PushDownContext=[[PROJECT->[host], LIMIT->10000], OpenSearchRequestBuilder(sourceBuilder={"from":0,"size":10000,"timeout":"1m","_source":{"includes":["host"],"excludes":[]}}, requestedTotalSize=10000, pageSize=null, startFrom=0)])

integ-test/src/test/resources/expectedOutput/calcite_no_pushdown/access_struct_subfield_with_item.yaml

@@ -0,0 +1,9 @@
+calcite:
+  logical: |
+    LogicalSystemLimit(fetch=[10000], type=[QUERY_SIZE_LIMIT])
+      LogicalProject(host=[$0], info=[GEOIP('dummy-datasource':VARCHAR, $0)], info.dummy_sub_field=[ITEM(GEOIP('dummy-datasource':VARCHAR, $0), 'dummy_sub_field')])
+        CalciteLogicalIndexScan(table=[[OpenSearch, opensearch-sql_test_index_weblogs]])
+  physical: |
+    EnumerableLimit(fetch=[10000])
+      EnumerableCalc(expr#0..11=[{inputs}], expr#12=['dummy-datasource':VARCHAR], expr#13=[GEOIP($t12, $t0)], expr#14=['dummy_sub_field'], expr#15=[ITEM($t13, $t14)], host=[$t0], info=[$t13], info.dummy_sub_field=[$t15])
+        CalciteEnumerableIndexScan(table=[[OpenSearch, opensearch-sql_test_index_weblogs]])