Omit by-timestamp clause in timechart command

Signed-off-by: Yuanchun Shen <yuanchu@amazon.com>

Author: yuancu

ppl/src/main/java/org/opensearch/sql/ppl/utils/PPLQueryDataAnonymizer.java

@@ -522,12 +522,11 @@ public String visitChart(Chart node, String context) {
     chartCommand.append(" ").append(visitExpression(node.getAggregationFunction()));
 
     if (node.getRowSplit() != null && node.getColumnSplit() != null) {
-      chartCommand
-          .append(" by ")
-          .append(visitExpression(node.getRowSplit()))
-          .append(" ")
-          .append(visitExpression(node.getColumnSplit()));
-    } else if (node.getRowSplit() != null) {
+      chartCommand.append(" by");
+      // timechart command does not have to explicit the by-timestamp field clause
+      if (!isTimechart) chartCommand.append(" ").append(visitExpression(node.getRowSplit()));
+      chartCommand.append(" ").append(visitExpression(node.getColumnSplit()));
+    } else if (node.getRowSplit() != null && !isTimechart) {
       chartCommand.append(" by ").append(visitExpression(node.getRowSplit()));
     } else if (node.getColumnSplit() != null) {
       chartCommand.append(" by ").append(visitExpression(node.getColumnSplit()));

ppl/src/test/java/org/opensearch/sql/ppl/utils/PPLQueryDataAnonymizerTest.java

@@ -255,8 +255,12 @@ public void testReverseCommand() {
   @Test
   public void testTimechartCommand() {
     assertEquals(
-        "source=table | timechart count() by span(time_identifier, *** m) identifier",
+        "source=table | timechart count() by identifier",
         anonymize("source=t | timechart count() by host"));
+
+    assertEquals(
+        "source=table | timechart max(identifier)",
+        anonymize("source=t | timechart max(revenue)"));
   }
 
   @Test