planner: convert schema_name from NULL to "" for index advisor (#56943)

ref #12303

pkg/planner/indexadvisor/indexadvisor.go

@@ -153,14 +153,14 @@ func prepareQuerySet(ctx context.Context, sctx sessionctx.Context,
 }
 
 func loadQuerySetFromStmtSummary(sctx sessionctx.Context, option *Option) (s.Set[Query], error) {
-	template := `SELECT any_value(schema_name) as schema_name,
+	template := `SELECT any_value(ifnull(schema_name, "")) as schema_name,
 				any_value(query_sample_text) as query_sample_text,
 				sum(cast(exec_count as double)) as exec_count
 			FROM information_schema.statements_summary_history
 			WHERE stmt_type = "Select" AND
 				summary_begin_time >= date_sub(now(), interval 1 day) AND
 				prepared = 0 AND
-				upper(schema_name) not in ("MYSQL", "INFORMATION_SCHEMA", "METRICS_SCHEMA", "PERFORMANCE_SCHEMA")
+				upper(ifnull(schema_name, "")) not in ("MYSQL", "INFORMATION_SCHEMA", "METRICS_SCHEMA", "PERFORMANCE_SCHEMA")
 			GROUP BY digest
 			ORDER BY sum(exec_count) DESC
 			LIMIT %?`

pkg/util/stmtsummary/v2/tests/BUILD.bazel

@@ -8,7 +8,7 @@ go_test(
         "table_test.go",
     ],
     flaky = True,
-    shard_count = 13,
+    shard_count = 14,
     deps = [
         "//pkg/config",
         "//pkg/kv",

pkg/util/stmtsummary/v2/tests/table_test.go

@@ -55,6 +55,33 @@ func TestStmtSummaryIndexAdvisor(t *testing.T) {
 			"b \"Column [b] appear in Equal or Range Predicate clause(s) in query: select `b` from `test` . `t` where `b` = ?\""))
 }
 
+func TestStmtSummaryIndexAdvisorNullSchema(t *testing.T) {
+	setupStmtSummary()
+	defer closeStmtSummary()
+	store := testkit.CreateMockStore(t)
+	tk := newTestKitWithRoot(t, store)
+	tk.MustExec(`use test`)
+	tk.MustExec(`create table t (a int, b int, c int)`)
+
+	tk.MustQueryToErr(`recommend index run`) // no query
+
+	tk = testkit.NewTestKit(t, store)
+	require.NoError(t, tk.Session().Auth(&auth.UserIdentity{Username: "root", Hostname: "%"}, nil, nil, nil))
+	tk.MustQuery(`select a from test.t where a=1`) // schema_name in statement_summary is NULL
+
+	rs := tk.MustQuery(`recommend index run`).Sort().Rows()
+	require.Equal(t, rs[0][2], "idx_a")
+
+	tk.MustQuery(`select b from test.t where b=1`)
+	rs = tk.MustQuery(`recommend index run`).Sort().Rows()
+	require.Equal(t, rs[0][2], "idx_a")
+	require.Equal(t, rs[1][2], "idx_b")
+
+	tk.MustQuery(`select index_columns, index_details->'$.Reason' from mysql.index_advisor_results`).Check(
+		testkit.Rows("a \"Column [a] appear in Equal or Range Predicate clause(s) in query: select `a` from `test` . `t` where `a` = ?\"",
+			"b \"Column [b] appear in Equal or Range Predicate clause(s) in query: select `b` from `test` . `t` where `b` = ?\""))
+}
+
 func TestStmtSummaryTable(t *testing.T) {
 	setupStmtSummary()
 	defer closeStmtSummary()