sql: fix aggregation of statistics

Previously, because we were using a join, we were double
counting statistics when we had the same fingerprint in
memory and persisted that had more than one index
recommendation.
This commit adds a `DISTINCT` so we only count them once.

Fixes #85958

Release note: None

pkg/sql/crdb_internal.go

@@ -5571,7 +5571,7 @@ SELECT
   plan_hash,
   app_name,
   max(metadata) as metadata,
-  crdb_internal.merge_statement_stats(array_agg(statistics)),
+  crdb_internal.merge_statement_stats(array_agg(DISTINCT statistics)),
   max(sampled_plan),
   aggregation_interval,
   array_remove(array_agg(index_rec), NULL) AS index_recommendations

pkg/sql/logictest/testdata/logic_test/create_statements

@@ -1512,7 +1512,7 @@ CREATE VIEW crdb_internal.statement_statistics (
     plan_hash,
     app_name,
     max(metadata) AS metadata,
-    crdb_internal.merge_statement_stats(array_agg(statistics)),
+    crdb_internal.merge_statement_stats(array_agg(DISTINCT statistics)),
     max(sampled_plan),
     aggregation_interval,
     array_remove(array_agg(index_rec), NULL) AS index_recommendations
@@ -1571,7 +1571,7 @@ CREATE VIEW crdb_internal.statement_statistics (
     plan_hash,
     app_name,
     max(metadata) AS metadata,
-    crdb_internal.merge_statement_stats(array_agg(statistics)),
+    crdb_internal.merge_statement_stats(array_agg(DISTINCT statistics)),
     max(sampled_plan),
     aggregation_interval,
     array_remove(array_agg(index_rec), NULL) AS index_recommendations

pkg/sql/sqlstats/persistedsqlstats/reader_test.go

@@ -24,6 +24,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/sql/sqlstats"
 	"github.com/cockroachdb/cockroach/pkg/sql/sqlstats/persistedsqlstats"
 	"github.com/cockroachdb/cockroach/pkg/testutils/serverutils"
+	"github.com/cockroachdb/cockroach/pkg/testutils/skip"
 	"github.com/cockroachdb/cockroach/pkg/testutils/sqlutils"
 	"github.com/cockroachdb/cockroach/pkg/util/leaktest"
 	"github.com/cockroachdb/cockroach/pkg/util/log"
@@ -143,6 +144,66 @@ func TestPersistedSQLStatsRead(t *testing.T) {
 	})
 }
 
+// Testing same fingerprint having more than one index recommendation and
+// checking the aggregation on the crdb_internal.statement_statistics table.
+// Testing for issue #85958.
+func TestSQLStatsWithMultipleIdxRec(t *testing.T) {
+	defer leaktest.AfterTest(t)()
+	defer log.Scope(t).Close(t)
+
+	skip.UnderStressRace(t, "expensive tests")
+
+	fakeTime := stubTime{
+		aggInterval: time.Hour,
+	}
+	fakeTime.setTime(timeutil.Now())
+
+	testCluster := serverutils.StartNewTestCluster(t, 3 /* numNodes */, base.TestClusterArgs{
+		ServerArgs: base.TestServerArgs{
+			Knobs: base.TestingKnobs{
+				SQLStatsKnobs: &sqlstats.TestingKnobs{
+					StubTimeNow: fakeTime.Now,
+					AOSTClause:  "AS OF SYSTEM TIME '-1us'",
+				},
+			},
+		},
+	})
+	ctx := context.Background()
+	defer testCluster.Stopper().Stop(ctx)
+
+	sqlConn := sqlutils.MakeSQLRunner(testCluster.ServerConn(0 /* idx */))
+
+	sqlConn.Exec(t, "CREATE TABLE t1 (k INT, i INT, f FLOAT, s STRING)")
+	sqlConn.Exec(t, "CREATE TABLE t2 (k INT, i INT, s STRING)")
+
+	query := "SELECT t1.k FROM t1 JOIN t2 ON t1.k = t2.k WHERE t1.i > 3 AND t2.i > 3"
+	memorySelect := "SELECT statistics -> 'statistics' ->> 'cnt' as count, " +
+		"array_length(index_recommendations, 1) FROM " +
+		"crdb_internal.cluster_statement_statistics WHERE metadata ->> 'query' = " +
+		"'SELECT t1.k FROM t1 JOIN t2 ON t1.k = t2.k WHERE (t1.i > _) AND (t2.i > _)'"
+	combinedSelect := "SELECT statistics -> 'statistics' ->> 'cnt' as count, " +
+		"array_length(index_recommendations, 1) FROM " +
+		"crdb_internal.statement_statistics WHERE metadata ->> 'query' = " +
+		"'SELECT t1.k FROM t1 JOIN t2 ON t1.k = t2.k WHERE (t1.i > _) AND (t2.i > _)'"
+
+	// Execute enough times to have index recommendations generated.
+	// This will generate two recommendations.
+	for i := 0; i < 6; i++ {
+		sqlConn.Exec(t, query)
+	}
+	var cnt int64
+	var recs int64
+	// It must have the same count 6 on both in-memory and combined tables.
+	// This test when there are more than one recommendation, so adding this
+	// example that has 2 recommendations;
+	sqlConn.QueryRow(t, memorySelect).Scan(&cnt, &recs)
+	require.Equal(t, int64(6), cnt)
+	require.Equal(t, int64(2), recs)
+	sqlConn.QueryRow(t, combinedSelect).Scan(&cnt, &recs)
+	require.Equal(t, int64(6), cnt)
+	require.Equal(t, int64(2), recs)
+}
+
 func verifyStoredStmtFingerprints(
 	t *testing.T,
 	expectedStmtFingerprints map[string]int64,