fix unit tests

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

Author: RyanL1997

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

@@ -183,26 +183,29 @@ public void testMultisearchWithStats() {
             + "  LogicalAggregate(group=[{0}], count=[COUNT()])\n"
             + "    LogicalProject(type=[$8])\n"
             + "      LogicalUnion(all=[true])\n"
-            + "        LogicalProject(EMPNO=[$0], ENAME=[$1], JOB=[$2], MGR=[$3], HIREDATE=[$4],"
+            + "        LogicalFilter(condition=[=($7, 10)])\n"
+            + "          LogicalProject(EMPNO=[$0], ENAME=[$1], JOB=[$2], MGR=[$3], HIREDATE=[$4],"
             + " SAL=[$5], COMM=[$6], DEPTNO=[$7], type=['accounting':VARCHAR])\n"
-            + "          LogicalFilter(condition=[=($7, 10)])\n"
             + "            LogicalTableScan(table=[[scott, EMP]])\n"
-            + "        LogicalProject(EMPNO=[$0], ENAME=[$1], JOB=[$2], MGR=[$3], HIREDATE=[$4],"
+            + "        LogicalFilter(condition=[=($7, 20)])\n"
+            + "          LogicalProject(EMPNO=[$0], ENAME=[$1], JOB=[$2], MGR=[$3], HIREDATE=[$4],"
             + " SAL=[$5], COMM=[$6], DEPTNO=[$7], type=['research':VARCHAR])\n"
-            + "          LogicalFilter(condition=[=($7, 20)])\n"
             + "            LogicalTableScan(table=[[scott, EMP]])\n";
     verifyLogical(root, expectedLogical);
 
+    // SparkSQL reflects Filter above Project due to flush logic
     String expectedSparkSql =
         "SELECT COUNT(*) `count`, `type`\n"
+            + "FROM (SELECT *\n"
             + "FROM (SELECT `EMPNO`, `ENAME`, `JOB`, `MGR`, `HIREDATE`, `SAL`, `COMM`, `DEPTNO`,"
             + " 'accounting' `type`\n"
-            + "FROM `scott`.`EMP`\n"
+            + "FROM `scott`.`EMP`) `t`\n"
             + "WHERE `DEPTNO` = 10\n"
             + "UNION ALL\n"
-            + "SELECT `EMPNO`, `ENAME`, `JOB`, `MGR`, `HIREDATE`, `SAL`, `COMM`, `DEPTNO`,"
+            + "SELECT *\n"
+            + "FROM (SELECT `EMPNO`, `ENAME`, `JOB`, `MGR`, `HIREDATE`, `SAL`, `COMM`, `DEPTNO`,"
             + " 'research' `type`\n"
-            + "FROM `scott`.`EMP`\n"
+            + "FROM `scott`.`EMP`) `t1`\n"
             + "WHERE `DEPTNO` = 20) `t3`\n"
             + "GROUP BY `type`";
     verifyPPLToSparkSQL(root, expectedSparkSql);

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

@@ -38,19 +38,18 @@ public void testRegexBasic() {
   public void testRegexChainedFilters() {
     String ppl = "source=EMP | regex ENAME='A.*' | regex JOB='.*CLERK' | fields ENAME, JOB";
     RelNode root = getRelNode(ppl);
+    // Filter accumulation combines multiple regex conditions into a single Filter with AND
     String expectedLogical =
         "LogicalProject(ENAME=[$1], JOB=[$2])\n"
-            + "  LogicalFilter(condition=[REGEXP_CONTAINS($2, '.*CLERK':VARCHAR)])\n"
-            + "    LogicalFilter(condition=[REGEXP_CONTAINS($1, 'A.*':VARCHAR)])\n"
-            + "      LogicalTableScan(table=[[scott, EMP]])\n";
+            + "  LogicalFilter(condition=[AND(REGEXP_CONTAINS($1, 'A.*':VARCHAR),"
+            + " REGEXP_CONTAINS($2, '.*CLERK':VARCHAR))])\n"
+            + "    LogicalTableScan(table=[[scott, EMP]])\n";
     verifyLogical(root, expectedLogical);
 
     String expectedSparkSql =
         "SELECT `ENAME`, `JOB`\n"
-            + "FROM (SELECT *\n"
             + "FROM `scott`.`EMP`\n"
-            + "WHERE REGEXP_CONTAINS(`ENAME`, 'A.*')) `t`\n"
-            + "WHERE REGEXP_CONTAINS(`JOB`, '.*CLERK')";
+            + "WHERE REGEXP_CONTAINS(`ENAME`, 'A.*') AND REGEXP_CONTAINS(`JOB`, '.*CLERK')";
     verifyPPLToSparkSQL(root, expectedSparkSql);
   }