Fix testOptionalColumnAtATimeReaderWithSparseDocs (elastic#133781)

We should increment the timestamp for all documents; otherwise, the last 
two documents may share the same timestamp, resulting in an undefined
order between them.

Closes elastic#133766

Author: dnhatn

muted-tests.yml

@@ -615,9 +615,6 @@ tests:
 - class: org.elasticsearch.xpack.esql.qa.single_node.GenerativeIT
   method: test
   issue: https://github.com/elastic/elasticsearch/issues/133077
-- class: org.elasticsearch.index.codec.tsdb.es819.ES819TSDBDocValuesFormatTests
-  method: testOptionalColumnAtATimeReaderWithSparseDocs
-  issue: https://github.com/elastic/elasticsearch/issues/133766
 
 # Examples:
 #

server/src/test/java/org/elasticsearch/index/codec/tsdb/es819/ES819TSDBDocValuesFormatTests.java

@@ -939,13 +939,12 @@ public void testOptionalColumnAtATimeReaderWithSparseDocs() throws Exception {
             int numDocsPerQValue = 120;
             int numDocs = numDocsPerQValue * (1 + random().nextInt(40));
             Long[] temperatureValues = new Long[numDocs];
-
             long q = 1;
             for (int i = 1; i <= numDocs; i++) {
                 var d = new Document();
-                long timestamp = currentTimestamp;
                 // Index sorting doesn't work with NumericDocValuesField:
-                d.add(SortedNumericDocValuesField.indexedField(timestampField, timestamp));
+                d.add(SortedNumericDocValuesField.indexedField(timestampField, currentTimestamp));
+                currentTimestamp += 1000L;
                 d.add(new SortedNumericDocValuesField(counterField, currentCounter));
                 d.add(new SortedDocValuesField(counterAsStringField, new BytesRef(Long.toString(currentCounter))));
                 d.add(new SortedNumericDocValuesField(queryField, q));
@@ -962,7 +961,6 @@ public void testOptionalColumnAtATimeReaderWithSparseDocs() throws Exception {
                     iw.commit();
                 }
                 if (i < numDocs - 1) {
-                    currentTimestamp += 1000L;
                     currentCounter++;
                 }
             }