fix: fix bug can't match any group (#676)

pkg/mysql/thead/thead.go

@@ -78,6 +78,13 @@ var (
 		Col{Name: "expr", FieldType: consts.FieldTypeVarString},
 		Col{Name: "step", FieldType: consts.FieldTypeVarString},
 	}
+
+	OpenTables = Thead{
+		Col{Name: "Database", FieldType: consts.FieldTypeVarString},
+		Col{Name: "Table", FieldType: consts.FieldTypeVarString},
+		Col{Name: "In_use", FieldType: consts.FieldTypeInt24},
+		Col{Name: "Name_locked", FieldType: consts.FieldTypeInt24},
+	}
 )
 
 type Col struct {

pkg/runtime/optimize/dal/show_open_tables.go

@@ -64,29 +64,37 @@ func optimizeShowOpenTables(ctx context.Context, o *optimize.Optimizer) (proto.P
 		}
 	}
 
+	duplicates := make(map[string]struct{})
+
 	plans := make([]proto.Plan, 0, len(clusters))
 	for _, cluster := range clusters {
 		ns := namespace.Load(tenant, cluster)
 		// check every group from namespace
 		groups := ns.DBGroups()
 		for i := 0; i < len(groups); i++ {
-			var ret *dal.ShowOpenTablesPlan
-			if db, ok := stmt.Like(); ok && db == cluster {
-				// filter in cluster
-				show := ast.NewBaseShow(groups[i])
-				stmtCopy := ast.ShowOpenTables{BaseShow: &show}
-				ret = dal.NewShowOpenTablesPlan(&stmtCopy)
-			} else {
-				// no filter or can't match any group
-				ret = dal.NewShowOpenTablesPlan(stmt)
+			if db, ok := stmt.Like(); !ok || db == cluster {
+				var ret *dal.ShowOpenTablesPlan
+				if ok {
+					// filter in cluster
+					show := ast.NewBaseShow(groups[i])
+					stmtCopy := ast.ShowOpenTables{BaseShow: &show}
+					ret = dal.NewShowOpenTablesPlan(&stmtCopy, duplicates, false)
+				} else {
+					// no filter
+					ret = dal.NewShowOpenTablesPlan(stmt, duplicates, false)
+				}
+				ret.BindArgs(o.Args)
+				ret.SetInvertedShards(invertedShards)
+				ret.SetInvertedDatabases(invertedDatabases)
+				ret.SetDatabase(groups[i])
+				plans = append(plans, ret)
 			}
-			ret.BindArgs(o.Args)
-			ret.SetInvertedShards(invertedShards)
-			ret.SetInvertedDatabases(invertedDatabases)
-			ret.SetDatabase(groups[i])
-			plans = append(plans, ret)
 		}
 	}
+	if len(plans) == 0 {
+		// can't match any group
+		return dal.NewShowOpenTablesPlan(stmt, duplicates, true), nil
+	}
 
 	return &dml.CompositePlan{
 		Plans: plans,

pkg/runtime/plan/dal/show_open_tables.go

@@ -19,6 +19,7 @@ package dal
 
 import (
 	"context"
+	"github.com/arana-db/arana/pkg/mysql/thead"
 	"strings"
 )
 
@@ -43,14 +44,18 @@ type ShowOpenTablesPlan struct {
 	Database          string
 	Conn              proto.DB
 	Stmt              *ast.ShowOpenTables
-	invertedShards    map[string]string // phy table name -> logical table name
-	invertedDatabases map[string]string // phy database name -> logical database name
+	invertedShards    map[string]string   // phy table name -> logical table name
+	invertedDatabases map[string]string   // phy database name -> logical database name
+	duplicates        map[string]struct{} // filter duplicates
+	empty             bool                // if can't match any group, return empty result
 }
 
 // NewShowOpenTablesPlan create ShowTables Plan
-func NewShowOpenTablesPlan(stmt *ast.ShowOpenTables) *ShowOpenTablesPlan {
+func NewShowOpenTablesPlan(stmt *ast.ShowOpenTables, duplicates map[string]struct{}, empty bool) *ShowOpenTablesPlan {
 	return &ShowOpenTablesPlan{
-		Stmt: stmt,
+		Stmt:       stmt,
+		duplicates: duplicates,
+		empty:      empty,
 	}
 }
 
@@ -66,6 +71,10 @@ func (st *ShowOpenTablesPlan) ExecIn(ctx context.Context, conn proto.VConn) (pro
 		err     error
 	)
 
+	if st.empty {
+		return emptyRs(), nil
+	}
+
 	if err = st.Stmt.Restore(ast.RestoreDefault, &sb, &indexes); err != nil {
 		return nil, errors.WithStack(err)
 	}
@@ -86,9 +95,6 @@ func (st *ShowOpenTablesPlan) ExecIn(ctx context.Context, conn proto.VConn) (pro
 
 	fields, _ := ds.Fields()
 
-	// filter duplicates
-	duplicates := make(map[string]struct{})
-
 	// 1. convert to logical table name
 	// 2. filter duplicated table name
 	ds = dataset.Pipe(ds,
@@ -123,16 +129,24 @@ func (st *ShowOpenTablesPlan) ExecIn(ctx context.Context, conn proto.VConn) (pro
 			}
 
 			tableName := vr.Values()[1].String()
-			if _, ok := duplicates[tableName]; ok {
+			if _, ok := st.duplicates[tableName]; ok {
 				return false
 			}
-			duplicates[tableName] = struct{}{}
+			st.duplicates[tableName] = struct{}{}
 			return true
 		}),
 	)
 	return resultx.New(resultx.WithDataset(ds)), nil
 }
 
+func emptyRs() proto.Result {
+	columns := thead.OpenTables.ToFields()
+	ds := &dataset.VirtualDataset{
+		Columns: columns,
+	}
+	return resultx.New(resultx.WithDataset(ds))
+}
+
 func (st *ShowOpenTablesPlan) SetDatabase(database string) {
 	st.Database = database
 }