peng - simplify if

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

Author: RyanL1997

ppl/src/main/java/org/opensearch/sql/ppl/parser/AstBuilder.java

@@ -1003,25 +1003,23 @@ public UnresolvedPlan visitRexCommand(OpenSearchPPLParser.RexCommandContext ctx)
     int maxMatchLimit =
         (settings != null) ? settings.getSettingValue(Settings.Key.PPL_REX_MAX_MATCH_LIMIT) : 10;
 
+    int userMaxMatch = maxMatch.orElse(1);
     int effectiveMaxMatch;
-    if (maxMatch.isPresent()) {
-      if (maxMatch.get() == 0) {
-        effectiveMaxMatch = maxMatchLimit;
-      } else if (maxMatch.get() > maxMatchLimit) {
-        throw new IllegalArgumentException(
-            String.format(
-                "Rex command max_match value (%d) exceeds the configured limit (%d). "
-                    + "Consider using a smaller max_match value"
-                    + (settings != null
-                        ? " or adjust the plugins.ppl.rex.max_match.limit setting."
-                        : "."),
-                maxMatch.get(),
-                maxMatchLimit));
-      } else {
-        effectiveMaxMatch = maxMatch.get();
-      }
+
+    if (userMaxMatch == 0) {
+      effectiveMaxMatch = maxMatchLimit;
+    } else if (userMaxMatch > maxMatchLimit) {
+      throw new IllegalArgumentException(
+          String.format(
+              "Rex command max_match value (%d) exceeds the configured limit (%d). "
+                  + "Consider using a smaller max_match value"
+                  + (settings != null
+                      ? " or adjust the plugins.ppl.rex.max_match.limit setting."
+                      : "."),
+              userMaxMatch,
+              maxMatchLimit));
     } else {
-      effectiveMaxMatch = 1;
+      effectiveMaxMatch = userMaxMatch;
     }
 
     return new Rex(field, pattern, mode, Optional.of(effectiveMaxMatch));