feedback: Changes in response to PR feedback

storage/engine_schema.go

@@ -17,7 +17,8 @@ func (e *Engine) TagKeys(ctx context.Context, orgID, bucketID influxdb.ID, start
 	// * All tag keys;
 	// * All tag keys filtered by an arbitrary predicate, e.g., tag keys for a measurement or tag keys appearing alongside another tag key pair.
 	//
-	return cursors.EmptyStringIterator
+
+	return cursors.NewStringSliceIterator([]string{"\x00", "arch", "cluster_id", "datacenter", "hostname", "os", "rack", "region", "service", "service_environment", "service_version", "\xff"})
 }
 
 // TagValues returns an iterator which enumerates the values for the specific
@@ -31,12 +32,4 @@ func (e *Engine) TagValues(ctx context.Context, orgID, bucketID influxdb.ID, tag
 	}
 
 	return e.engine.TagValues(ctx, orgID, bucketID, tagKey, start, end, predicate)
-
-	// This method would be invoked when the consumer wants to get the following schema information for an arbitrary
-	// time range in a single bucket:
-	//
-	// * All measurement names, i.e. tagKey == _measurement);
-	// * All field names for a specific measurement using a predicate
-	//     * i.e. tagKey is "_field", predicate _measurement == "<measurement>"
-	//
 }

tsdb/cursors/arrayvalues.gen.go

@@ -1109,8 +1109,7 @@ func (a *TimestampArray) Exclude(min, max int64) {
 }
 
 // Contains returns true if values exist between min and max inclusive. The
-// values must be deduplicated and sorted before calling Contains or the
+// values must be sorted before calling Contains or the results are undefined.
-// results are undefined.
 func (a *TimestampArray) Contains(min, max int64) bool {
 	rmin, rmax := a.FindRange(min, max)
 	if rmin == -1 && rmax == -1 {

tsdb/cursors/arrayvalues.gen.go.tmpl

@@ -238,8 +238,7 @@ func (a *{{ $typename }}) Exclude(min, max int64) {
 }
 
 // Contains returns true if values exist between min and max inclusive. The
-// values must be deduplicated and sorted before calling Contains or the
+// values must be sorted before calling Contains or the results are undefined.
-// results are undefined.
 func (a *{{ $typename }}) Contains(min, max int64) bool {
 	rmin, rmax := a.FindRange(min, max)
 	if rmin == -1 && rmax == -1 {

tsdb/tsm1/encoding.go

@@ -115,8 +115,8 @@ func (a Values) Encode(buf []byte) ([]byte, error) {
 }
 
 // Contains returns true if values exist for the time interval [min, max]
-// inclusive. The values must be deduplicated and sorted before calling
+// inclusive. The values must be sorted before calling Contains or the
-// Contains or the results are undefined.
+// results are undefined.
 func (a Values) Contains(min, max int64) bool {
 	rmin, rmax := a.FindRange(min, max)
 	if rmin == -1 && rmax == -1 {

tsdb/tsm1/engine_schema.go

@@ -20,20 +20,11 @@ import (
 func (e *Engine) TagValues(ctx context.Context, orgID, bucketID influxdb.ID, tagKey string, start, end int64, predicate influxql.Expr) (cursors.StringIterator, error) {
 	encoded := tsdb.EncodeName(orgID, bucketID)
 
-	var tagKeyBytes []byte
-	if tagKey == "_measurement" {
-		tagKeyBytes = models.MeasurementTagKeyBytes
-	} else if tagKey == "_field" {
-		tagKeyBytes = models.FieldKeyTagKeyBytes
-	} else {
-		tagKeyBytes = []byte(tagKey)
-	}
-
 	if predicate == nil {
-		return e.tagValuesNoPredicate(ctx, encoded[:], tagKeyBytes, start, end)
+		return e.tagValuesNoPredicate(ctx, encoded[:], []byte(tagKey), start, end)
 	}
 
-	return e.tagValuesPredicate(ctx, encoded[:], tagKeyBytes, start, end, predicate)
+	return e.tagValuesPredicate(ctx, encoded[:], []byte(tagKey), start, end, predicate)
 }
 
 func (e *Engine) tagValuesNoPredicate(ctx context.Context, orgBucket, tagKeyBytes []byte, start, end int64) (cursors.StringIterator, error) {

tsdb/tsm1/engine_schema_test.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/google/go-cmp/cmp"
 	"github.com/influxdata/influxdb"
+	"github.com/influxdata/influxdb/models"
 	"github.com/influxdata/influxdb/tsdb/cursors"
 	"github.com/influxdata/influxdb/tsdb/tsm1"
 	"github.com/influxdata/influxql"
@@ -164,12 +165,12 @@ memB,host=EB,os=macOS value=1.3 201`)
 			exp: nil,
 		},
 
-		// _measurement tag
+		// models.MeasurementTagKey tag
 		{
 			name: "_measurement/all",
 			args: args{
 				org: 0,
-				key: "_measurement",
+				key: models.MeasurementTagKey,
 				min: 0,
 				max: 399,
 			},
@@ -179,7 +180,7 @@ memB,host=EB,os=macOS value=1.3 201`)
 			name: "_measurement/some",
 			args: args{
 				org: 0,
-				key: "_measurement",
+				key: models.MeasurementTagKey,
 				min: 205,
 				max: 399,
 			},

tsdb/tsm1/reader_index_iterator.go

@@ -1,9 +1,11 @@
 package tsm1
 
 import (
-	"fmt"
+	"errors"
 )
 
+var errKeyCountChanged = errors.New("TSMIndexIterator: key count changed during iteration")
+
 // TSMIndexIterator allows one to iterate over the TSM index.
 type TSMIndexIterator struct {
 	b    *faultBuffer
@@ -31,7 +33,7 @@ type TSMIndexIterator struct {
 func (t *TSMIndexIterator) Next() bool {
 	t.d.mu.RLock()
 	if n := len(t.d.ro.offsets); t.n != n {
-		t.err, t.ok = fmt.Errorf("Key count changed during iteration"), false
+		t.err, t.ok = errKeyCountChanged, false
 	}
 	if !t.ok || t.err != nil {
 		t.d.mu.RUnlock()
@@ -65,7 +67,7 @@ func (t *TSMIndexIterator) Next() bool {
 func (t *TSMIndexIterator) Seek(key []byte) (exact, ok bool) {
 	t.d.mu.RLock()
 	if n := len(t.d.ro.offsets); t.n != n {
-		t.err, t.ok = fmt.Errorf("Key count changed during iteration"), false
+		t.err, t.ok = errKeyCountChanged, false
 	}
 	if t.err != nil {
 		t.d.mu.RUnlock()