executor: support 'SHOW CONFIG' syntax to show configs of PD and TiKV instances

executor/memtable_reader.go

@@ -143,7 +143,10 @@ func (e *clusterConfigRetriever) retrieve(_ context.Context, sctx sessionctx.Con
 		return nil, nil
 	}
 	e.retrieved = true
+	return fetchClusterConfig(sctx, e.extractor.NodeTypes, e.extractor.Instances)
+}
 
+func fetchClusterConfig(sctx sessionctx.Context, nodeTypes, nodeAddrs set.StringSet) ([][]types.Datum, error) {
 	type result struct {
 		idx  int
 		rows [][]types.Datum
@@ -159,7 +162,7 @@ func (e *clusterConfigRetriever) retrieve(_ context.Context, sctx sessionctx.Con
 	if err != nil {
 		return nil, err
 	}
-	serversInfo = filterClusterServerInfo(serversInfo, e.extractor.NodeTypes, e.extractor.Instances)
+	serversInfo = filterClusterServerInfo(serversInfo, nodeTypes, nodeAddrs)
 
 	var finalRows [][]types.Datum
 	wg := sync.WaitGroup{}

executor/show.go

@@ -58,6 +58,7 @@ import (
 	"github.com/pingcap/tidb/util/format"
 	"github.com/pingcap/tidb/util/hack"
 	"github.com/pingcap/tidb/util/hint"
+	"github.com/pingcap/tidb/util/set"
 	"github.com/pingcap/tidb/util/sqlexec"
 	"github.com/pingcap/tidb/util/stringutil"
 )
@@ -127,6 +128,8 @@ func (e *ShowExec) fetchAll(ctx context.Context) error {
 		return e.fetchShowCollation()
 	case ast.ShowColumns:
 		return e.fetchShowColumns(ctx)
+	case ast.ShowConfig:
+		return e.fetchShowClusterConfigs(ctx)
 	case ast.ShowCreateTable:
 		return e.fetchShowCreateTable()
 	case ast.ShowCreateSequence:
@@ -963,6 +966,34 @@ func (e *ShowExec) fetchShowCreateSequence() error {
 	return nil
 }
 
+// TestShowClusterConfigKey is the key used to store TestShowClusterConfigFunc.
+var TestShowClusterConfigKey stringutil.StringerStr = "TestShowClusterConfigKey"
+
+// TestShowClusterConfigFunc is used to test 'show config ...'.
+type TestShowClusterConfigFunc func() ([][]types.Datum, error)
+
+func (e *ShowExec) fetchShowClusterConfigs(ctx context.Context) error {
+	emptySet := set.NewStringSet()
+	var confItems [][]types.Datum
+	var err error
+	if f := e.ctx.Value(TestShowClusterConfigKey); f != nil {
+		confItems, err = f.(TestShowClusterConfigFunc)()
+	} else {
+		confItems, err = fetchClusterConfig(e.ctx, emptySet, emptySet)
+	}
+	if err != nil {
+		return err
+	}
+	for _, items := range confItems {
+		row := make([]interface{}, 0, 4)
+		for _, item := range items {
+			row = append(row, item.GetString())
+		}
+		e.appendRow(row)
+	}
+	return nil
+}
+
 func (e *ShowExec) fetchShowCreateTable() error {
 	tb, err := e.getTable()
 	if err != nil {

executor/show_test.go

@@ -27,6 +27,7 @@ import (
 	plannercore "github.com/pingcap/tidb/planner/core"
 	"github.com/pingcap/tidb/session"
 	"github.com/pingcap/tidb/sessionctx"
+	"github.com/pingcap/tidb/types"
 	"github.com/pingcap/tidb/util/testkit"
 	"github.com/pingcap/tidb/util/testutil"
 )
@@ -791,3 +792,37 @@ func (s *testSuite5) TestShowBuiltin(c *C) {
 	c.Assert("abs", Equals, rows[0][0].(string))
 	c.Assert("yearweek", Equals, rows[267][0].(string))
 }
+
+func (s *testSuite5) TestShowClusterConfig(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+
+	var confItems [][]types.Datum
+	var confErr error
+	var confFunc executor.TestShowClusterConfigFunc = func() ([][]types.Datum, error) {
+		return confItems, confErr
+	}
+	tk.Se.SetValue(executor.TestShowClusterConfigKey, confFunc)
+	strs2Items := func(strs ...string) []types.Datum {
+		items := make([]types.Datum, 0, len(strs))
+		for _, s := range strs {
+			items = append(items, types.NewStringDatum(s))
+		}
+		return items
+	}
+	confItems = append(confItems, strs2Items("tidb", "127.0.0.1:1111", "log.level", "info"))
+	confItems = append(confItems, strs2Items("pd", "127.0.0.1:2222", "log.level", "info"))
+	confItems = append(confItems, strs2Items("tikv", "127.0.0.1:3333", "log.level", "info"))
+	tk.MustQuery("show config").Check(testkit.Rows(
+		"tidb 127.0.0.1:1111 log.level info",
+		"pd 127.0.0.1:2222 log.level info",
+		"tikv 127.0.0.1:3333 log.level info"))
+	tk.MustQuery("show config where type='tidb'").Check(testkit.Rows(
+		"tidb 127.0.0.1:1111 log.level info"))
+	tk.MustQuery("show config where type like '%ti%'").Check(testkit.Rows(
+		"tidb 127.0.0.1:1111 log.level info",
+		"tikv 127.0.0.1:3333 log.level info"))
+
+	confErr = fmt.Errorf("something unknown error")
+	c.Assert(tk.QueryToErr("show config"), ErrorMatches, confErr.Error())
+}

planner/core/planbuilder.go

@@ -2920,6 +2920,8 @@ func buildShowSchema(s *ast.ShowStmt, isView bool, isSequence bool) (schema *exp
 		return buildTableRegionsSchema()
 	case ast.ShowEngines:
 		names = []string{"Engine", "Support", "Comment", "Transactions", "XA", "Savepoints"}
+	case ast.ShowConfig:
+		names = []string{"Type", "Instance", "Name", "Value"}
 	case ast.ShowDatabases:
 		names = []string{"Database"}
 	case ast.ShowOpenTables: