fix the UTs

Signed-off-by: Jialiang Liang <jiallian@amazon.com>

Author: RyanL1997

ppl/src/test/java/org/opensearch/sql/ppl/calcite/CalcitePPLAbstractTest.java

@@ -22,9 +22,13 @@
 import lombok.Getter;
 import org.apache.calcite.plan.Contexts;
 import org.apache.calcite.plan.RelTraitDef;
+import org.apache.calcite.plan.hep.HepPlanner;
+import org.apache.calcite.plan.hep.HepProgram;
+import org.apache.calcite.plan.hep.HepProgramBuilder;
 import org.apache.calcite.rel.RelNode;
 import org.apache.calcite.rel.rel2sql.RelToSqlConverter;
 import org.apache.calcite.rel.rel2sql.SqlImplementor;
+import org.apache.calcite.rel.rules.FilterMergeRule;
 import org.apache.calcite.schema.SchemaPlus;
 import org.apache.calcite.sql.SqlNode;
 import org.apache.calcite.sql.parser.SqlParser;
@@ -101,10 +105,19 @@ public RelNode getRelNode(String ppl) {
     Query query = (Query) plan(pplParser, ppl);
     planTransformer.analyze(query.getPlan(), context);
     RelNode root = context.relBuilder.build();
+    root = mergeAdjacentFilters(root);
     System.out.println(root.explain());
     return root;
   }
 
+  private RelNode mergeAdjacentFilters(RelNode relNode) {
+    HepProgram program =
+        new HepProgramBuilder().addRuleInstance(FilterMergeRule.Config.DEFAULT.toRule()).build();
+    HepPlanner planner = new HepPlanner(program);
+    planner.setRoot(relNode);
+    return planner.findBestExp();
+  }
+
   private Node plan(PPLSyntaxParser parser, String query) {
     final AstStatementBuilder builder =
         new AstStatementBuilder(

ppl/src/test/java/org/opensearch/sql/ppl/calcite/CalcitePPLTrendlineTest.java

@@ -76,9 +76,8 @@ public void testTrendlineMultipleFields() {
             + " DEPTNO_trendline=[CASE(>(COUNT() OVER (ROWS 1 PRECEDING), 1), /(SUM($7) OVER (ROWS"
             + " 1 PRECEDING), CAST(COUNT($7) OVER (ROWS 1 PRECEDING)):DOUBLE NOT NULL),"
             + " null:NULL)])\n"
-            + "  LogicalFilter(condition=[IS NOT NULL($7)])\n"
-            + "    LogicalFilter(condition=[IS NOT NULL($5)])\n"
-            + "      LogicalTableScan(table=[[scott, EMP]])\n";
+            + "  LogicalFilter(condition=[AND(IS NOT NULL($5), IS NOT NULL($7))])\n"
+            + "    LogicalTableScan(table=[[scott, EMP]])\n";
     verifyLogical(root, expectedLogical);
 
     String expectedSparkSql =
@@ -89,10 +88,8 @@ public void testTrendlineMultipleFields() {
             + " BETWEEN 1 PRECEDING AND CURRENT ROW)) > 1 THEN (SUM(`DEPTNO`) OVER (ROWS BETWEEN 1"
             + " PRECEDING AND CURRENT ROW)) / CAST(COUNT(`DEPTNO`) OVER (ROWS BETWEEN 1 PRECEDING"
             + " AND CURRENT ROW) AS DOUBLE) ELSE NULL END `DEPTNO_trendline`\n"
-            + "FROM (SELECT *\n"
             + "FROM `scott`.`EMP`\n"
-            + "WHERE `SAL` IS NOT NULL) `t`\n"
-            + "WHERE `DEPTNO` IS NOT NULL";
+            + "WHERE `SAL` IS NOT NULL AND `DEPTNO` IS NOT NULL";
     verifyPPLToSparkSQL(root, expectedSparkSql);
   }
 }