[milo] {buildbucket,buildbot,swarming,logdog} -> backends/*.

milo/appengine/buildbot/datastore.go

-// Copyright 2016 The LUCI Authors. All rights reserved.
-// Use of this source code is governed under the Apache License, Version 2.0
-// that can be found in the LICENSE file.
-
-package buildbot
-
-import (
-        "github.com/luci/gae/service/datastore"
-
-        "golang.org/x/net/context"
-)
-
-// buildQueryBatchSize is the batch size to use when querying build. It is
-// employed as an upper bound by getBuildQueryBatcher.
-//
-// This should be tuned to the observed query timeout for build loading. Since
-// loading is CPU-bound, this will probably be low. If build queries start
-// encountering datastore timeouts, reduce this value.
-const buildQueryBatchSize = 50
-
-// getBuildQueryBatcher returns a datastore.Batcher tuned for executing queries on the
-// "buildbotBuild" entity.
-func getBuildQueryBatcher(c context.Context) *datastore.Batcher {
-        constraints := datastore.Raw(c).Constraints()
-        if constraints.QueryBatchSize > buildQueryBatchSize {
-                constraints.QueryBatchSize = buildQueryBatchSize
-        }
-        return &datastore.Batcher{
-                Size: constraints.QueryBatchSize,
-        }
-}
-
-// runBuildsQuery takes a buildbotBuild query and returns a list of builds
-// along with a cursor.  We pass the limit here and apply it to the query as
-// an optimization because then we can create a build container of that size.
-func runBuildsQuery(c context.Context, q *datastore.Query, limit int32) (
-        []*buildbotBuild, *datastore.Cursor, error) {
-
-        if limit != 0 {
-                q = q.Limit(limit)
-        }
-        builds := make([]*buildbotBuild, 0, limit)
-        var nextCursor *datastore.Cursor
-        err := getBuildQueryBatcher(c).Run(
-                c, q, func(build *buildbotBuild, getCursor datastore.CursorCB) error {
-                        builds = append(builds, build)
-                        tmpCursor, err := getCursor()
-                        if err != nil {
-                                return err
-                        }
-                        nextCursor = &tmpCursor
-                        return nil
-                })
-        return builds, nextCursor, err
-}