infoschema, planner: fix wrong table_names in statement summary

infoschema/perfschema/tables_test.go

@@ -117,14 +117,28 @@ func (s *testTableSuite) TestStmtSummaryTable(c *C) {
 	tk.MustExec("create table p(a int primary key, b int)")
 	for i := 1; i < 3; i++ {
 		tk.MustQuery("select b from p where a=1")
-		expectedResult := fmt.Sprintf("%d \tPoint_Get_1\troot\t1\ttable:p, handle:1", i)
+		expectedResult := fmt.Sprintf("%d \tPoint_Get_1\troot\t1\ttable:p, handle:1 %s", i, "test.p")
 		// Also make sure that the plan digest is not empty
-		tk.MustQuery(`select exec_count, plan
+		tk.MustQuery(`select exec_count, plan, table_names
 			from performance_schema.events_statements_summary_by_digest
 			where digest_text like 'select b from p%' and plan_digest != ''`,
 		).Check(testkit.Rows(expectedResult))
 	}
 
+	// Point get another database.
+	tk.MustQuery("select variable_value from mysql.tidb where variable_name = 'system_tz'")
+	tk.MustQuery(`select table_names
+			from performance_schema.events_statements_summary_by_digest
+			where digest_text like 'select variable_value%' and schema_name='test'`,
+	).Check(testkit.Rows("mysql.tidb"))
+
+	// Test `create database`.
+	tk.MustExec("create database if not exists test")
+	tk.MustQuery(`select table_names
+			from performance_schema.events_statements_summary_by_digest
+			where digest_text like 'create database%' and schema_name='test'`,
+	).Check(testkit.Rows("<nil>"))
+
 	// Test SELECT.
 	const failpointName = "github.com/pingcap/tidb/planner/core/mockPlanRowCount"
 	c.Assert(failpoint.Enable(failpointName, "return(100)"), IsNil)

planner/core/point_get_plan.go

@@ -735,7 +735,7 @@ func newPointGetPlan(ctx sessionctx.Context, dbName string, schema *expression.S
 		outputNames:  names,
 		LockWaitTime: ctx.GetSessionVars().LockWaitTimeout,
 	}
-	ctx.GetSessionVars().StmtCtx.Tables = []stmtctx.TableEntry{{DB: ctx.GetSessionVars().CurrentDB, Table: tbl.Name.L}}
+	ctx.GetSessionVars().StmtCtx.Tables = []stmtctx.TableEntry{{DB: dbName, Table: tbl.Name.L}}
 	return p
 }
 

util/stmtsummary/statement_summary.go

@@ -500,6 +500,10 @@ func (ssbd *stmtSummaryByDigest) init(sei *StmtExecInfo, beginTime int64, interv
 	// Use "," to separate table names to support FIND_IN_SET.
 	var buffer bytes.Buffer
 	for i, value := range sei.StmtCtx.Tables {
+		// In `create database` statement, DB name is not empty but table name is empty.
+		if len(value.Table) == 0 {
+			continue
+		}
 		buffer.WriteString(strings.ToLower(value.DB))
 		buffer.WriteString(".")
 		buffer.WriteString(strings.ToLower(value.Table))