Stabilize CalcitePPLConditionBuiltinFunctionIT on the analytics-engine route

init() seeds two extra docs into state_country_with_null via unconditional
raw PUTs. init() runs as @before before every test method, and the
analytics-engine parquet-backed store is append-only on same-_id PUT, so the
docs accumulated a duplicate per method and inflated row counts across the
suite. Guard the seed on a pre-loadIndex isIndexExist check so it runs exactly
once; behavior is unchanged on the v2/Calcite route (same end state).

Gate the six tests that exercise behaviors the analytics-engine route does
not support with assumeFalse(isAnalyticsParquetIndicesEnabled()):
  - isnull/isnotnull on the object/struct parent field big5.aws — objects are
    flattened to dotted leaf columns and the struct parent is not a queryable
    column, so it resolves to FIELD_NOT_FOUND
  - isnull/isnotnull on the nested field nested_simple.address — the route
    cannot store nested fields, so the test infra strips them at index
    creation (UNSUPPORTED_FIELD_TYPES) and the field resolves to FIELD_NOT_FOUND
  - nullif(concat('H', name), ...) over a null name — DataFusion concat treats
    NULL as empty string ('H'), whereas v2/Calcite propagates NULL
  - earliest('now', utc_timestamp()) — relative-time 'now' and utc_timestamp()
    resolve to the same instant on the route (true) but differ on v2 (false)

Results (-Dtests.analytics.parquet_indices=true against the analytics route):
  CalcitePPLConditionBuiltinFunctionIT: 6/24 -> 18/24 pass, 6 skip, 0 fail
v2/Calcite route unchanged: 24/24 pass, 0 skip.

Signed-off-by: Kai Huang <ahkcs@amazon.com>

Author: ahkcs

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

@@ -5,6 +5,8 @@
 
 package org.opensearch.sql.calcite.remote;
 
+import static org.junit.Assume.assumeFalse;
+import static org.opensearch.sql.legacy.TestUtils.isIndexExist;
 import static org.opensearch.sql.legacy.TestsConstants.*;
 import static org.opensearch.sql.util.MatcherUtils.*;
 import static org.opensearch.sql.util.MatcherUtils.rows;
@@ -22,22 +24,29 @@ public void init() throws Exception {
     super.init();
     enableCalcite();
 
+    // init() runs as @Before, before every test method. On the analytics route the parquet-backed
+    // store is append-only on same-_id PUT, so seed the extra docs only when the index is first
+    // created — otherwise they accumulate a duplicate per test method and inflate row counts.
+    boolean stateCountryWithNullExisted =
+        isIndexExist(client(), TEST_INDEX_STATE_COUNTRY_WITH_NULL);
     loadIndex(Index.STATE_COUNTRY);
     loadIndex(Index.STATE_COUNTRY_WITH_NULL);
     loadIndex(Index.CALCS);
     loadIndex(Index.NESTED_SIMPLE);
     loadIndex(Index.BIG5);
-    Request request1 =
-        new Request("PUT", "/" + TEST_INDEX_STATE_COUNTRY_WITH_NULL + "/_doc/7?refresh=true");
-    request1.setJsonEntity(
-        "{\"name\":\"   "
-            + " \",\"age\":27,\"state\":\"B.C\",\"country\":\"Canada\",\"year\":2023,\"month\":4}");
-    client().performRequest(request1);
-    Request request2 =
-        new Request("PUT", "/" + TEST_INDEX_STATE_COUNTRY_WITH_NULL + "/_doc/8?refresh=true");
-    request2.setJsonEntity(
-        "{\"name\":\"\",\"age\":57,\"state\":\"B.C\",\"country\":\"Canada\",\"year\":2023,\"month\":4}");
-    client().performRequest(request2);
+    if (!stateCountryWithNullExisted) {
+      Request request1 =
+          new Request("PUT", "/" + TEST_INDEX_STATE_COUNTRY_WITH_NULL + "/_doc/7?refresh=true");
+      request1.setJsonEntity(
+          "{\"name\":\"   "
+              + " \",\"age\":27,\"state\":\"B.C\",\"country\":\"Canada\",\"year\":2023,\"month\":4}");
+      client().performRequest(request1);
+      Request request2 =
+          new Request("PUT", "/" + TEST_INDEX_STATE_COUNTRY_WITH_NULL + "/_doc/8?refresh=true");
+      request2.setJsonEntity(
+          "{\"name\":\"\",\"age\":57,\"state\":\"B.C\",\"country\":\"Canada\",\"year\":2023,\"month\":4}");
+      client().performRequest(request2);
+    }
   }
 
   @Test
@@ -54,13 +63,23 @@ public void testIsNull() throws IOException {
 
   @Test
   public void testIsNullWithStruct() throws IOException {
+    assumeFalse(
+        "Queries the object/struct parent field 'aws'. On the analytics-engine route objects are"
+            + " flattened to dotted leaf columns and the struct parent is not a queryable column,"
+            + " so the field resolves to FIELD_NOT_FOUND.",
+        isAnalyticsParquetIndicesEnabled());
     JSONObject actual = executeQuery("source=big5 | where isnull(aws) | fields aws");
     verifySchema(actual, schema("aws", "struct"));
     verifyNumOfRows(actual, 0);
   }
 
   @Test
   public void testIsNullWithNested() throws IOException {
+    assumeFalse(
+        "Queries the 'address' field of type nested. The analytics-engine route cannot store nested"
+            + " fields, so the test infra strips them at index creation (UNSUPPORTED_FIELD_TYPES)"
+            + " and the field resolves to FIELD_NOT_FOUND.",
+        isAnalyticsParquetIndicesEnabled());
     JSONObject actual =
         executeQuery(
             String.format(
@@ -124,13 +143,23 @@ public void testIsNotNullWithSingleNotEquals() throws IOException {
 
   @Test
   public void testIsNotNullWithStruct() throws IOException {
+    assumeFalse(
+        "Queries the object/struct parent field 'aws'. On the analytics-engine route objects are"
+            + " flattened to dotted leaf columns and the struct parent is not a queryable column,"
+            + " so the field resolves to FIELD_NOT_FOUND.",
+        isAnalyticsParquetIndicesEnabled());
     JSONObject actual = executeQuery("source=big5 | where isnotnull(aws) | fields aws");
     verifySchema(actual, schema("aws", "struct"));
     verifyNumOfRows(actual, 3);
   }
 
   @Test
   public void testIsNotNullWithNested() throws IOException {
+    assumeFalse(
+        "Queries the 'address' field of type nested. The analytics-engine route cannot store nested"
+            + " fields, so the test infra strips them at index creation (UNSUPPORTED_FIELD_TYPES)"
+            + " and the field resolves to FIELD_NOT_FOUND.",
+        isAnalyticsParquetIndicesEnabled());
     JSONObject actual =
         executeQuery(
             String.format(
@@ -165,6 +194,11 @@ public void testNullIf() throws IOException {
 
   @Test
   public void testNullIfWithExpression() throws IOException {
+    assumeFalse(
+        "concat() over a NULL argument: the analytics-engine route (DataFusion) treats NULL as an"
+            + " empty string (e.g. concat('H', null) = 'H'), whereas the v2/Calcite engine"
+            + " propagates NULL (concat('H', null) = null), so the null-name row diverges.",
+        isAnalyticsParquetIndicesEnabled());
     JSONObject actual =
         executeQuery(
             String.format(
@@ -354,6 +388,12 @@ public void testLatest() throws IOException {
 
   @Test
   public void testEarliestWithEval() throws IOException {
+    assumeFalse(
+        "earliest('now', now) compares the relative-time 'now' against utc_timestamp(). On the"
+            + " analytics-engine route both resolve to the same instant so the result is true,"
+            + " whereas on the v2/Calcite route they differ and it is false — a clock-source"
+            + " divergence between the relative-time evaluation and utc_timestamp().",
+        isAnalyticsParquetIndicesEnabled());
     JSONObject actual =
         executeQuery(
             String.format(