storage/db: optimize query terms matching "upload"

Since the upload ID is part of the primary key, we can avoid using the
RecordLabels table to find matching records. This takes the query
"upload:20170127.22 name:Gzip" from ~0.3s to ~0.04s on our production
database.

Change-Id: Id31624ec1b81f3a7f648c6597392718c56a10edd
Reviewed-on: https://go-review.googlesource.com/37236
Run-TryBot: Quentin Smith <quentin@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

storage/db/db.go

@@ -155,7 +155,7 @@ func (db *DB) prepareStatements(driverName string) error {
 
 // An Upload is a collection of files that share an upload ID.
 type Upload struct {
-	// ID is the value of the "uploadid" key that should be
+	// ID is the value of the "upload" key that should be
 	// associated with every record in this upload.
 	ID string
 

storage/db/db_test.go

@@ -250,6 +250,7 @@ func TestQuery(t *testing.T) {
 	for i := 0; i < 1024; i++ {
 		allRecords = append(allRecords, i)
 		r := &benchfmt.Result{Labels: make(map[string]string), NameLabels: make(map[string]string), Content: "BenchmarkName 1 ns/op"}
+		r.Labels["upload"] = u.ID
 		for j := uint(0); j < 10; j++ {
 			r.Labels[fmt.Sprintf("label%d", j)] = fmt.Sprintf("%d", i/(1<<j))
 		}
@@ -280,6 +281,11 @@ func TestQuery(t *testing.T) {
 		{"", allRecords},
 		{"missing>", []int{}},
 		{"label0>", allRecords},
+		{"upload:" + u.ID, allRecords},
+		{"upload:none", []int{}},
+		{"upload>" + u.ID, []int{}},
+		{"upload<" + u.ID, []int{}},
+		{"label0:0 upload:" + u.ID, []int{0}},
 	}
 	for _, test := range tests {
 		t.Run("query="+test.q, func(t *testing.T) {

storage/db/query.go

@@ -133,6 +133,18 @@ func (p part) merge(p2 part) (part, error) {
 
 // sql returns a SQL expression and a list of arguments for finding records matching p.
 func (p part) sql() (sql string, args []interface{}, err error) {
+	if p.key == "upload" {
+		switch p.operator {
+		case equals:
+			return "SELECT UploadID, RecordID FROM Records WHERE UploadID = ?", []interface{}{p.value}, nil
+		case lt:
+			return "SELECT UploadID, RecordID FROM Records WHERE UploadID < ?", []interface{}{p.value}, nil
+		case gt:
+			return "SELECT UploadID, RecordID FROM Records WHERE UploadID > ?", []interface{}{p.value}, nil
+		case ltgt:
+			return "SELECT UploadID, RecordID FROM Records WHERE UploadID < ? AND UploadID > ?", []interface{}{p.value, p.value2}, nil
+		}
+	}
 	switch p.operator {
 	case equals:
 		if p.value == "" {