From 6d05f845cabdf3fd78d9dbfb570a35f1849cb9cc Mon Sep 17 00:00:00 2001
From: djshow832 <873581766@qq.com>
Date: Mon, 9 Mar 2020 17:54:16 +0800
Subject: [PATCH] infoschema, planner: fix wrong `table_names` in statement
 summary (#15228)

---
 infoschema/perfschema/tables_test.go  | 18 ++++++++++++++++--
 planner/core/point_get_plan.go        |  2 +-
 util/stmtsummary/statement_summary.go |  4 ++++
 3 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/infoschema/perfschema/tables_test.go b/infoschema/perfschema/tables_test.go
index caa6ded05fab8..3e11bd30f1592 100644
--- a/infoschema/perfschema/tables_test.go
+++ b/infoschema/perfschema/tables_test.go
@@ -107,14 +107,28 @@ 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)
diff --git a/planner/core/point_get_plan.go b/planner/core/point_get_plan.go
index 50861087f67b5..94d5fca0997ea 100644
--- a/planner/core/point_get_plan.go
+++ b/planner/core/point_get_plan.go
@@ -308,7 +308,7 @@ func newPointGetPlan(ctx sessionctx.Context, dbName string, schema *expression.S
 		TblInfo:      tbl,
 		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
 }
 
diff --git a/util/stmtsummary/statement_summary.go b/util/stmtsummary/statement_summary.go
index 7d48b064694de..b63986976fe55 100644
--- a/util/stmtsummary/statement_summary.go
+++ b/util/stmtsummary/statement_summary.go
@@ -501,6 +501,10 @@ 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))