*: support show stats_extended to inspect extended stats cache

executor/show.go

@@ -177,6 +177,8 @@ func (e *ShowExec) fetchAll(ctx context.Context) error {
 		return e.fetchShowProcessList()
 	case ast.ShowEvents:
 		// empty result
+	case ast.ShowStatsExtended:
+		return e.fetchShowStatsExtended()
 	case ast.ShowStatsMeta:
 		return e.fetchShowStatsMeta()
 	case ast.ShowStatsHistograms:

executor/show_stats.go

@@ -14,17 +14,88 @@
 package executor
 
 import (
+	"fmt"
 	"sort"
+	"strings"
 	"time"
 
 	"github.com/pingcap/errors"
+	"github.com/pingcap/parser/ast"
+	"github.com/pingcap/parser/model"
 	"github.com/pingcap/parser/mysql"
 	"github.com/pingcap/tidb/domain"
 	"github.com/pingcap/tidb/statistics"
 	"github.com/pingcap/tidb/store/tikv/oracle"
 	"github.com/pingcap/tidb/types"
 )
 
+func (e *ShowExec) fetchShowStatsExtended() error {
+	do := domain.GetDomain(e.ctx)
+	h := do.StatsHandle()
+	dbs := do.InfoSchema().AllSchemas()
+	for _, db := range dbs {
+		for _, tblInfo := range db.Tables {
+			pi := tblInfo.GetPartitionInfo()
+			// Extended statistics for partitioned table is not supported now.
+			if pi != nil {
+				continue
+			}
+			e.appendTableForStatsExtended(db.Name.L, tblInfo, h.GetTableStats(tblInfo))
+		}
+	}
+	return nil
+}
+
+func (e *ShowExec) appendTableForStatsExtended(dbName string, tbl *model.TableInfo, statsTbl *statistics.Table) {
+	if statsTbl.Pseudo || statsTbl.ExtendedStats == nil || len(statsTbl.ExtendedStats.Stats) == 0 {
+		return
+	}
+	colID2Name := make(map[int64]string, len(tbl.Columns))
+	for _, col := range tbl.Columns {
+		colID2Name[col.ID] = col.Name.L
+	}
+	var sb strings.Builder
+	for statsName, item := range statsTbl.ExtendedStats.Stats {
+		sb.WriteString("[")
+		for i, colID := range item.ColIDs {
+			name, ok := colID2Name[colID]
+			if ok {
+				sb.WriteString(name)
+			} else {
+				sb.WriteString("?")
+			}
+			if i != len(item.ColIDs)-1 {
+				sb.WriteString(",")
+			}
+		}
+		sb.WriteString("]")
+		colNames := sb.String()
+		sb.Reset()
+		var statsType, statsVal string
+		switch item.Tp {
+		case ast.StatsTypeCorrelation:
+			statsType = "correlation"
+			statsVal = fmt.Sprintf("%f", item.ScalarVals)
+		case ast.StatsTypeDependency:
+			statsType = "dependency"
+			statsVal = item.StringVals
+		case ast.StatsTypeCardinality:
+			statsType = "cardinality"
+			statsVal = item.StringVals
+		}
+		e.appendRow([]interface{}{
+			dbName,
+			tbl.Name.L,
+			statsName,
+			colNames,
+			statsType,
+			statsVal,
+			// Same LastUpdateVersion for records of the same table, mainly for debug purpose on product env.
+			statsTbl.ExtendedStats.LastUpdateVersion,
+		})
+	}
+}
+
 func (e *ShowExec) fetchShowStatsMeta() error {
 	do := domain.GetDomain(e.ctx)
 	h := do.StatsHandle()

executor/show_stats_test.go

@@ -261,3 +261,53 @@ func (s *testShowStatsSuite) TestShowStatusSnapshot(c *C) {
 	result := tk.MustQuery("show table status;")
 	c.Check(result.Rows()[0][0], Matches, "t")
 }
+
+func (s *testShowStatsSuite) TestShowStatsExtended(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	s.domain.StatsHandle().Clear()
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("create table t (a int, b int, c int)")
+	tk.MustExec("insert into t values(1,1,3),(2,2,2),(3,3,1)")
+
+	tk.MustExec("set session tidb_enable_extended_stats = on")
+	tk.MustExec("alter table t add stats_extended s1 correlation(a,b)")
+	tk.MustExec("alter table t add stats_extended s2 correlation(a,c)")
+	tk.MustQuery("select name, status from mysql.stats_extended where name like 's%'").Sort().Check(testkit.Rows(
+		"s1 0",
+		"s2 0",
+	))
+	result := tk.MustQuery("show stats_extended where db_name = 'test' and table_name = 't'")
+	c.Assert(len(result.Rows()), Equals, 0)
+
+	tk.MustExec("analyze table t")
+	tk.MustQuery("select name, status from mysql.stats_extended where name like 's%'").Sort().Check(testkit.Rows(
+		"s1 1",
+		"s2 1",
+	))
+	result = tk.MustQuery("show stats_extended where db_name = 'test' and table_name = 't'").Sort()
+	c.Assert(len(result.Rows()), Equals, 2)
+	c.Assert(result.Rows()[0][0], Equals, "test")
+	c.Assert(result.Rows()[0][1], Equals, "t")
+	c.Assert(result.Rows()[0][2], Equals, "s1")
+	c.Assert(result.Rows()[0][3], Equals, "[a,b]")
+	c.Assert(result.Rows()[0][4], Equals, "correlation")
+	c.Assert(result.Rows()[0][5], Equals, "1.000000")
+	c.Assert(result.Rows()[1][0], Equals, "test")
+	c.Assert(result.Rows()[1][1], Equals, "t")
+	c.Assert(result.Rows()[1][2], Equals, "s2")
+	c.Assert(result.Rows()[1][3], Equals, "[a,c]")
+	c.Assert(result.Rows()[1][4], Equals, "correlation")
+	c.Assert(result.Rows()[1][5], Equals, "-1.000000")
+	c.Assert(result.Rows()[1][6], Equals, result.Rows()[0][6])
+
+	tk.MustExec("alter table t drop stats_extended s1")
+	tk.MustExec("alter table t drop stats_extended s2")
+	tk.MustQuery("select name, status from mysql.stats_extended where name like 's%'").Sort().Check(testkit.Rows(
+		"s1 2",
+		"s2 2",
+	))
+	s.domain.StatsHandle().Update(s.domain.InfoSchema())
+	result = tk.MustQuery("show stats_extended where db_name = 'test' and table_name = 't'")
+	c.Assert(len(result.Rows()), Equals, 0)
+}

planner/core/planbuilder.go

@@ -2142,7 +2142,7 @@ func (b *PlanBuilder) buildShow(ctx context.Context, show *ast.ShowStmt) (Plan,
 		p.setSchemaAndNames(buildShowNextRowID())
 		b.visitInfo = appendVisitInfo(b.visitInfo, mysql.SelectPriv, show.Table.Schema.L, show.Table.Name.L, "", ErrPrivilegeCheckFail)
 		return p, nil
-	case ast.ShowStatsBuckets, ast.ShowStatsHistograms, ast.ShowStatsMeta, ast.ShowStatsHealthy, ast.ShowStatsTopN:
+	case ast.ShowStatsBuckets, ast.ShowStatsHistograms, ast.ShowStatsMeta, ast.ShowStatsExtended, ast.ShowStatsHealthy, ast.ShowStatsTopN:
 		user := b.ctx.GetSessionVars().User
 		var err error
 		if user != nil {
@@ -3663,6 +3663,9 @@ func buildShowSchema(s *ast.ShowStmt, isView bool, isSequence bool) (schema *exp
 	case ast.ShowStatsMeta:
 		names = []string{"Db_name", "Table_name", "Partition_name", "Update_time", "Modify_count", "Row_count"}
 		ftypes = []byte{mysql.TypeVarchar, mysql.TypeVarchar, mysql.TypeVarchar, mysql.TypeDatetime, mysql.TypeLonglong, mysql.TypeLonglong}
+	case ast.ShowStatsExtended:
+		names = []string{"Db_name", "Table_name", "Stats_name", "Column_names", "Stats_type", "Stats_val", "Last_update_version"}
+		ftypes = []byte{mysql.TypeVarchar, mysql.TypeVarchar, mysql.TypeVarchar, mysql.TypeVarchar, mysql.TypeVarchar, mysql.TypeVarchar, mysql.TypeLonglong}
 	case ast.ShowStatsHistograms:
 		names = []string{"Db_name", "Table_name", "Partition_name", "Column_name", "Is_index", "Update_time", "Distinct_count", "Null_count", "Avg_col_size", "Correlation"}
 		ftypes = []byte{mysql.TypeVarchar, mysql.TypeVarchar, mysql.TypeVarchar, mysql.TypeVarchar, mysql.TypeTiny, mysql.TypeDatetime,