SQL: prevent duplicate generation for repeated aggs (#33252)

Prevent generation of duplicate aggs caused by repetitive functions,
leading to invalid query.

Fix #30287

Author: costin

x-pack/plugin/sql/src/main/java/org/elasticsearch/xpack/sql/querydsl/agg/Aggs.java

@@ -112,6 +112,9 @@ public Aggs addGroups(Collection<GroupByKey> groups) {
     }
 
     public Aggs addAgg(LeafAgg agg) {
+        if (metricAggs.contains(agg)) {
+            return this;
+        }
         return new Aggs(groups, combine(metricAggs, agg), pipelineAggs);
     }
 

x-pack/qa/sql/src/main/resources/agg.sql-spec

@@ -394,4 +394,12 @@ SELECT MIN(salary) min, MAX(salary) max, gender g, languages l, COUNT(*) c FROM
 aggMultiWithHavingOnCount
 SELECT MIN(salary) min, MAX(salary) max, gender g, COUNT(*) c FROM "test_emp" WHERE languages > 0 GROUP BY g HAVING c > 40 ORDER BY gender;
 aggMultiGroupByMultiWithHavingOnCount
-SELECT MIN(salary) min, MAX(salary) max, gender g, languages l, COUNT(*) c FROM "test_emp" WHERE languages > 0 GROUP BY g, languages HAVING c > 40 ORDER BY gender, languages;
+SELECT MIN(salary) min, MAX(salary) max, gender g, languages l, COUNT(*) c FROM "test_emp" WHERE languages > 0 GROUP BY g, languages HAVING c > 40 ORDER BY gender, languages;
+
+// repetion of same aggs to check whether the generated query contains duplicates or not
+aggRepeatFunctionAcrossFields
+SELECT MIN(emp_no) AS a, 1 + MIN(emp_no) AS b, ABS(MIN(emp_no)) AS c FROM test_emp;
+aggRepeatFunctionBetweenSelectAndHaving
+SELECT gender, COUNT(DISTINCT languages) AS c FROM test_emp GROUP BY gender HAVING count(DISTINCT languages) > 0 ORDER BY gender;
+
+