Support sorting by time desc

CHANGELOG.md

@@ -10,6 +10,7 @@ With this release InfluxDB is moving to Go 1.5.
 - [#3901](https://github.com/influxdb/influxdb/pull/3901): Add consistency level option to influx cli Thanks @takayuki
 - [#3876](https://github.com/influxdb/influxdb/pull/3876): Allow the following syntax in CQs: INTO "1hPolicy".:MEASUREMENT
 - [#3975](https://github.com/influxdb/influxdb/pull/3975): Add shard copy service
+- [#3986](https://github.com/influxdb/influxdb/pull/3986): Support sorting by time desc
 
 ### Bugfixes
 - [#3804](https://github.com/influxdb/influxdb/pull/3804): init.d script fixes, fixes issue 3803.

cmd/influxd/run/server_test.go

@@ -2201,6 +2201,14 @@ func TestServer_Query_Aggregates(t *testing.T) {
 			command: `SELECT sum(value)/2 FROM load`,
 			exp:     `{"results":[{"series":[{"name":"load","columns":["time",""],"values":[["1970-01-01T00:00:00Z",75]]}]}]}`,
 		},
+
+		// order by time desc
+		&Query{
+			name:    "order by time desc",
+			params:  url.Values{"db": []string{"db0"}},
+			command: `SELECT max(value) FROM intmany where time >= '2000-01-01T00:00:00Z' AND time <= '2000-01-01T00:01:00Z' group by time(10s) order by time desc`,
+			exp:     `{"results":[{"series":[{"name":"intmany","columns":["time","max"],"values":[["2000-01-01T00:01:00Z",7],["2000-01-01T00:00:50Z",5],["2000-01-01T00:00:40Z",5],["2000-01-01T00:00:30Z",4],["2000-01-01T00:00:20Z",4],["2000-01-01T00:00:10Z",4],["2000-01-01T00:00:00Z",2]]}]}]}`,
+		},
 	}...)
 
 	for i, query := range test.queries {
@@ -3877,3 +3885,51 @@ func TestServer_Query_EvilIdentifiers(t *testing.T) {
 		}
 	}
 }
+
+func TestServer_Query_OrderByTime(t *testing.T) {
+	t.Parallel()
+	s := OpenServer(NewConfig(), "")
+	defer s.Close()
+
+	if err := s.CreateDatabaseAndRetentionPolicy("db0", newRetentionPolicyInfo("rp0", 1, 0)); err != nil {
+		t.Fatal(err)
+	}
+	if err := s.MetaStore.SetDefaultRetentionPolicy("db0", "rp0"); err != nil {
+		t.Fatal(err)
+	}
+
+	writes := []string{
+		fmt.Sprintf(`cpu,host=server1 value=1 %d`, mustParseTime(time.RFC3339Nano, "2000-01-01T00:00:01Z").UnixNano()),
+		fmt.Sprintf(`cpu,host=server1 value=2 %d`, mustParseTime(time.RFC3339Nano, "2000-01-01T00:00:02Z").UnixNano()),
+		fmt.Sprintf(`cpu,host=server1 value=3 %d`, mustParseTime(time.RFC3339Nano, "2000-01-01T00:00:03Z").UnixNano()),
+	}
+
+	test := NewTest("db0", "rp0")
+	test.write = strings.Join(writes, "\n")
+
+	test.addQueries([]*Query{
+		&Query{
+			name:    "order on points",
+			params:  url.Values{"db": []string{"db0"}},
+			command: `select value from "cpu" ORDER BY time DESC`,
+			exp:     `{"results":[{"series":[{"name":"cpu","columns":["time","value"],"values":[["2000-01-01T00:00:03Z",3],["2000-01-01T00:00:02Z",2],["2000-01-01T00:00:01Z",1]]}]}]}`,
+		},
+	}...)
+
+	for i, query := range test.queries {
+		if i == 0 {
+			if err := test.init(s); err != nil {
+				t.Fatalf("test init failed: %s", err)
+			}
+		}
+		if query.skip {
+			t.Logf("SKIP:: %s", query.name)
+			continue
+		}
+		if err := query.Execute(s); err != nil {
+			t.Error(query.Error(err))
+		} else if !query.success() {
+			t.Error(query.failureMessage())
+		}
+	}
+}

influxql/ast.go

@@ -276,7 +276,7 @@ type SortField struct {
 // String returns a string representation of a sort field
 func (field *SortField) String() string {
 	var buf bytes.Buffer
-	if field.Name == "" {
+	if field.Name != "" {
 		_, _ = buf.WriteString(field.Name)
 		_, _ = buf.WriteString(" ")
 	}

influxql/parser.go

@@ -1809,24 +1809,29 @@ func (p *Parser) parseOrderBy() (SortFields, error) {
 func (p *Parser) parseSortFields() (SortFields, error) {
 	var fields SortFields
 
-	// If first token is ASC or DESC, all fields are sorted.
-	if tok, pos, lit := p.scanIgnoreWhitespace(); tok == ASC || tok == DESC {
-		if tok == DESC {
-			// Token must be ASC, until other sort orders are supported.
-			return nil, errors.New("only ORDER BY time ASC supported at this time")
-		}
-		return append(fields, &SortField{Ascending: (tok == ASC)}), nil
-	} else if tok != IDENT {
-		return nil, newParseError(tokstr(tok, lit), []string{"identifier", "ASC", "DESC"}, pos)
-	}
-	p.unscan()
+	tok, pos, lit := p.scanIgnoreWhitespace()
 
-	// At least one field is required.
-	field, err := p.parseSortField()
-	if err != nil {
-		return nil, err
+	switch tok {
+	// The first field after an order by may not have a field name (e.g. ORDER BY ASC)
+	case ASC, DESC:
+		fields = append(fields, &SortField{Ascending: (tok == ASC)})
+	// If it's a token, parse it as a sort field.  At least one is required.
+	case IDENT:
+		p.unscan()
+		field, err := p.parseSortField()
+		if err != nil {
+			return nil, err
+		}
+
+		if lit != "time" {
+			return nil, errors.New("only ORDER BY time supported at this time")
+		}
+
+		fields = append(fields, field)
+	// Parse error...
+	default:
+		return nil, newParseError(tokstr(tok, lit), []string{"identifier", "ASC", "DESC"}, pos)
 	}
-	fields = append(fields, field)
 
 	// Parse additional fields.
 	for {
@@ -1845,9 +1850,8 @@ func (p *Parser) parseSortFields() (SortFields, error) {
 		fields = append(fields, field)
 	}
 
-	// First SortField must be time ASC, until other sort orders are supported.
-	if len(fields) > 1 || fields[0].Name != "time" || !fields[0].Ascending {
-		return nil, errors.New("only ORDER BY time ASC supported at this time")
+	if len(fields) > 1 {
+		return nil, errors.New("only ORDER BY time supported at this time")
 	}
 
 	return fields, nil

influxql/parser_test.go

@@ -76,8 +76,7 @@ func TestParser_ParseStatement(t *testing.T) {
 
 		// SELECT statement
 		{
-			skip: true,
-			s:    fmt.Sprintf(`SELECT mean(field1), sum(field2) ,count(field3) AS field_x FROM myseries WHERE host = 'hosta.influxdb.org' and time > '%s' GROUP BY time(10h) ORDER BY ASC LIMIT 20 OFFSET 10;`, now.UTC().Format(time.RFC3339Nano)),
+			s: fmt.Sprintf(`SELECT mean(field1), sum(field2) ,count(field3) AS field_x FROM myseries WHERE host = 'hosta.influxdb.org' and time > '%s' GROUP BY time(10h) ORDER BY DESC LIMIT 20 OFFSET 10;`, now.UTC().Format(time.RFC3339Nano)),
 			stmt: &influxql.SelectStatement{
 				IsRawQuery: false,
 				Fields: []*influxql.Field{
@@ -101,7 +100,7 @@ func TestParser_ParseStatement(t *testing.T) {
 				},
 				Dimensions: []*influxql.Dimension{{Expr: &influxql.Call{Name: "time", Args: []influxql.Expr{&influxql.DurationLiteral{Val: 10 * time.Hour}}}}},
 				SortFields: []*influxql.SortField{
-					{Ascending: true},
+					{Ascending: false},
 				},
 				Limit:  20,
 				Offset: 10,
@@ -587,17 +586,17 @@ func TestParser_ParseStatement(t *testing.T) {
 		// SHOW SERIES WHERE with ORDER BY and LIMIT
 		{
 			skip: true,
-			s:    `SHOW SERIES WHERE region = 'uswest' ORDER BY ASC, field1, field2 DESC LIMIT 10`,
+			s:    `SHOW SERIES WHERE region = 'order by desc' ORDER BY DESC, field1, field2 DESC LIMIT 10`,
 			stmt: &influxql.ShowSeriesStatement{
 				Condition: &influxql.BinaryExpr{
 					Op:  influxql.EQ,
 					LHS: &influxql.VarRef{Val: "region"},
-					RHS: &influxql.StringLiteral{Val: "uswest"},
+					RHS: &influxql.StringLiteral{Val: "order by desc"},
 				},
 				SortFields: []*influxql.SortField{
-					{Ascending: true},
-					{Name: "field1"},
-					{Name: "field2"},
+					&influxql.SortField{Ascending: false},
+					&influxql.SortField{Name: "field1", Ascending: true},
+					&influxql.SortField{Name: "field2"},
 				},
 				Limit: 10,
 			},
@@ -1260,10 +1259,7 @@ func TestParser_ParseStatement(t *testing.T) {
 		{s: `SELECT field1 FROM myseries ORDER BY /`, err: `found /, expected identifier, ASC, DESC at line 1, char 38`},
 		{s: `SELECT field1 FROM myseries ORDER BY 1`, err: `found 1, expected identifier, ASC, DESC at line 1, char 38`},
 		{s: `SELECT field1 FROM myseries ORDER BY time ASC,`, err: `found EOF, expected identifier at line 1, char 47`},
-		{s: `SELECT field1 FROM myseries ORDER BY DESC`, err: `only ORDER BY time ASC supported at this time`},
-		{s: `SELECT field1 FROM myseries ORDER BY field1`, err: `only ORDER BY time ASC supported at this time`},
-		{s: `SELECT field1 FROM myseries ORDER BY time DESC`, err: `only ORDER BY time ASC supported at this time`},
-		{s: `SELECT field1 FROM myseries ORDER BY time, field1`, err: `only ORDER BY time ASC supported at this time`},
+		{s: `SELECT field1 FROM myseries ORDER BY time, field1`, err: `only ORDER BY time supported at this time`},
 		{s: `SELECT field1 AS`, err: `found EOF, expected identifier at line 1, char 18`},
 		{s: `SELECT field1 FROM foo group by time(1s)`, err: `GROUP BY requires at least one aggregate function`},
 		{s: `SELECT count(value), value FROM foo`, err: `mixing aggregate and non-aggregate queries is not supported`},
@@ -1440,7 +1436,8 @@ func TestParser_ParseStatement(t *testing.T) {
 		if !reflect.DeepEqual(tt.err, errstring(err)) {
 			t.Errorf("%d. %q: error mismatch:\n  exp=%s\n  got=%s\n\n", i, tt.s, tt.err, err)
 		} else if tt.err == "" && !reflect.DeepEqual(tt.stmt, stmt) {
-			t.Logf("\nexp=%s\ngot=%s\n", mustMarshalJSON(tt.stmt), mustMarshalJSON(stmt))
+			t.Logf("\n# %s\nexp=%s\ngot=%s\n", tt.s, mustMarshalJSON(tt.stmt), mustMarshalJSON(stmt))
+			t.Logf("\nSQL exp=%s\nSQL got=%s\n", tt.stmt.String(), stmt.String())
 			t.Errorf("%d. %q\n\nstmt mismatch:\n\nexp=%#v\n\ngot=%#v\n\n", i, tt.s, tt.stmt, stmt)
 		}
 	}

tsdb/cursor.go

@@ -5,20 +5,48 @@ import (
 	"container/heap"
 )
 
+// Direction represents a cursor navigation direction.
+type Direction bool
+
+const (
+	// Forward indicates that a cursor will move forward over its values.
+	Forward Direction = true
+	// Reverse indicates that a cursor will move backwards over its values.
+	Reverse Direction = false
+)
+
+func (d Direction) String() string {
+	if d.Forward() {
+		return "forward"
+	}
+	return "reverse"
+}
+
+// Forward returns true if direction is forward
+func (d Direction) Forward() bool {
+	return d == Forward
+}
+
+// Forward returns true if direction is reverse
+func (d Direction) Reverse() bool {
+	return d == Reverse
+}
+
 // MultiCursor returns a single cursor that combines the results of all cursors in order.
 //
 // If the same key is returned from multiple cursors then the first cursor
 // specified will take precendence. A key will only be returned once from the
 // returned cursor.
-func MultiCursor(cursors ...Cursor) Cursor {
-	return &multiCursor{cursors: cursors}
+func MultiCursor(d Direction, cursors ...Cursor) Cursor {
+	return &multiCursor{cursors: cursors, direction: d}
 }
 
 // multiCursor represents a cursor that combines multiple cursors into one.
 type multiCursor struct {
-	cursors []Cursor
-	heap    cursorHeap
-	prev    []byte
+	cursors   []Cursor
+	heap      cursorHeap
+	prev      []byte
+	direction Direction
 }
 
 // Seek moves the cursor to a given key.
@@ -48,6 +76,8 @@ func (mc *multiCursor) Seek(seek []byte) (key, value []byte) {
 	return mc.pop()
 }
 
+func (mc *multiCursor) Direction() Direction { return mc.direction }
+
 // Next returns the next key/value from the cursor.
 func (mc *multiCursor) Next() (key, value []byte) { return mc.pop() }
 
@@ -90,7 +120,12 @@ type cursorHeap []*cursorHeapItem
 func (h cursorHeap) Len() int      { return len(h) }
 func (h cursorHeap) Swap(i, j int) { h[i], h[j] = h[j], h[i] }
 func (h cursorHeap) Less(i, j int) bool {
-	if cmp := bytes.Compare(h[i].key, h[j].key); cmp == -1 {
+	dir := -1
+	if !h[i].cursor.Direction() {
+		dir = 1
+	}
+
+	if cmp := bytes.Compare(h[i].key, h[j].key); cmp == dir {
 		return true
 	} else if cmp == 0 {
 		return h[i].priority > h[j].priority