infoschema: fix snapshot read bug for information_schema.tables (#55830)

close #55827
pingcap · Sep 4, 2024 · 7ea6526 · 7ea6526
1 parent 2bd5660
commit 7ea6526
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Showing 3 changed files with 42 additions and 9 deletions.
diff --git a/pkg/infoschema/infoschema_v2.go b/pkg/infoschema/infoschema_v2.go
@@ -653,19 +653,23 @@ type TableItem struct {
 
 // IterateAllTableItems is used for special performance optimization.
 // Used by executor/infoschema_reader.go to handle reading from INFORMATION_SCHEMA.TABLES.
+// If visit return false, stop the iterate process.
 func (is *infoschemaV2) IterateAllTableItems(visit func(TableItem) bool) {
-	pivot, ok := is.byName.Max()
+	max, ok := is.byName.Max()
 	if !ok {
 		return
 	}
-	if !visit(TableItem{DBName: pivot.dbName, TableName: pivot.tableName}) {
-		return
-	}
-	is.byName.Descend(pivot, func(item tableItem) bool {
-		if pivot.dbName == item.dbName && pivot.tableName == item.tableName {
-			return true // skip MVCC version
+	var pivot *tableItem
+	is.byName.Descend(max, func(item tableItem) bool {
+		if item.schemaVersion > is.schemaMetaVersion {
+			// skip MVCC version, those items are not visible to the queried schema version
+			return true
 		}
-		pivot = item
+		if pivot != nil && pivot.dbName == item.dbName && pivot.tableName == item.tableName {
+			// skip MVCC version, this db.table has been visited already
+			return true
+		}
+		pivot = &item
 		if !item.tomb {
 			return visit(TableItem{DBName: item.dbName, TableName: item.tableName})
 		}

diff --git a/pkg/infoschema/test/infoschemav2test/BUILD.bazel b/pkg/infoschema/test/infoschemav2test/BUILD.bazel
@@ -8,7 +8,7 @@ go_test(
         "v2_test.go",
     ],
     flaky = True,
-    shard_count = 10,
+    shard_count = 11,
     deps = [
         "//pkg/domain",
         "//pkg/domain/infosync",

diff --git a/pkg/infoschema/test/infoschemav2test/v2_test.go b/pkg/infoschema/test/infoschemav2test/v2_test.go
@@ -504,3 +504,32 @@ func TestSchemaSimpleTableInfos(t *testing.T) {
 	require.Equal(t, tblInfos[0].Name.L, "t2")
 	require.Equal(t, tblInfos[1].Name.L, "t1")
 }
+
+func TestSnapshotInfoschemaReader(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	// For mocktikv, safe point is not initialized, we manually insert it for snapshot to use.
+	safePointName := "tikv_gc_safe_point"
+	safePointValue := "20160102-15:04:05 -0700"
+	safePointComment := "All versions after safe point can be accessed. (DO NOT EDIT)"
+	updateSafePoint := fmt.Sprintf(`INSERT INTO mysql.tidb VALUES ('%[1]s', '%[2]s', '%[3]s')
+	ON DUPLICATE KEY
+	UPDATE variable_value = '%[2]s', comment = '%[3]s'`, safePointName, safePointValue, safePointComment)
+	tk.MustExec(updateSafePoint)
+
+	tk.MustExec("create database issue55827")
+	tk.MustExec("use issue55827")
+
+	time1 := time.Now()
+	timeStr := time1.Format("2006-1-2 15:04:05.000")
+
+	tk.MustExec("create table t (id int primary key);")
+	tk.MustQuery("select count(*) from INFORMATION_SCHEMA.TABLES where table_schema = 'issue55827'").Check(testkit.Rows("1"))
+	tk.MustQuery("select count(tidb_table_id) from INFORMATION_SCHEMA.TABLES where table_schema = 'issue55827'").Check(testkit.Rows("1"))
+
+	// For issue 55827
+	sql := fmt.Sprintf("select count(*) from INFORMATION_SCHEMA.TABLES as of timestamp '%s' where table_schema = 'issue55827'", timeStr)
+	tk.MustQuery(sql).Check(testkit.Rows("0"))
+	sql = fmt.Sprintf("select * from INFORMATION_SCHEMA.TABLES as of timestamp '%s' where table_schema = 'issue55827'", timeStr)
+	tk.MustQuery(sql).Check(testkit.Rows())
+}