func newProjectionStrategy(fq *ds.FinalizedQuery, rq *reducedQuery, cb ds.RawRunCB) queryStrategy {
proj := fq.Project()
projectionLookups := make([]projectionLookup, len(proj))
for i, prop := range proj {
projectionLookups[i].propertyName = prop
lookupErr := fmt.Errorf("planning a strategy for an unfulfillable query?")
for j, col := range rq.suffixFormat {
if col.Property == prop {
projectionLookups[i].suffixIndex = j
lookupErr = nil
break
}
}
impossible(lookupErr)
}
ret := &projectionStrategy{cb: cb, project: projectionLookups}
if fq.Distinct() {
ret.distinct = stringset.New(0)
}
return ret
}
func (d rdsImpl) fixQuery(fq *ds.FinalizedQuery) (*datastore.Query, error) {
ret := datastore.NewQuery(fq.Kind())
start, end := fq.Bounds()
if start != nil {
ret = ret.Start(start.(datastore.Cursor))
}
if end != nil {
ret = ret.End(end.(datastore.Cursor))
}
for prop, vals := range fq.EqFilters() {
if prop == "__ancestor__" {
p, err := dsF2RProp(d.aeCtx, vals[0])
if err != nil {
return nil, err
}
ret = ret.Ancestor(p.Value.(*datastore.Key))
} else {
filt := prop + "="
for _, v := range vals {
p, err := dsF2RProp(d.aeCtx, v)
if err != nil {
return nil, err
}
ret = ret.Filter(filt, p.Value)
}
}
}
if lnam, lop, lprop := fq.IneqFilterLow(); lnam != "" {
p, err := dsF2RProp(d.aeCtx, lprop)
if err != nil {
return nil, err
}
ret = ret.Filter(lnam+" "+lop, p.Value)
}
if hnam, hop, hprop := fq.IneqFilterHigh(); hnam != "" {
p, err := dsF2RProp(d.aeCtx, hprop)
if err != nil {
return nil, err
}
ret = ret.Filter(hnam+" "+hop, p.Value)
}
if fq.EventuallyConsistent() {
ret = ret.EventualConsistency()
}
if fq.KeysOnly() {
ret = ret.KeysOnly()
}
if lim, ok := fq.Limit(); ok {
ret = ret.Limit(int(lim))
}
if off, ok := fq.Offset(); ok {
ret = ret.Offset(int(off))
}
for _, o := range fq.Orders() {
ret = ret.Order(o.String())
}
ret = ret.Project(fq.Project()...)
if fq.Distinct() {
ret = ret.Distinct()
}
return ret, nil
}
// runMergedQueries executes a user query `fq` against the parent datastore as
// well as the in-memory datastore, calling `cb` with the merged result set.
//
// It's expected that the caller of this function will apply limit and offset
// if the query contains those restrictions. This may convert the query to
// an expanded projection query with more data than the user asked for. It's the
// caller's responsibility to prune away the extra data.
//
// See also `dsTxnBuf.Run()`.
func runMergedQueries(fq *ds.FinalizedQuery, sizes *sizeTracker,
memDS, parentDS ds.RawInterface, cb func(k *ds.Key, data ds.PropertyMap) error) error {
toRun, err := adjustQuery(fq)
if err != nil {
return err
}
cmpLower, cmpUpper := memory.GetBinaryBounds(fq)
cmpOrder := fq.Orders()
cmpFn := func(i *item) string {
return i.getCmpRow(cmpLower, cmpUpper, cmpOrder)
}
dedup := stringset.Set(nil)
distinct := stringset.Set(nil)
distinctOrder := []ds.IndexColumn(nil)
if len(fq.Project()) > 0 { // the original query was a projection query
if fq.Distinct() {
// it was a distinct projection query, so we need to dedup by distinct
// options.
distinct = stringset.New(0)
proj := fq.Project()
distinctOrder = make([]ds.IndexColumn, len(proj))
for i, p := range proj {
distinctOrder[i].Property = p
}
}
} else {
// the original was a normal or keys-only query, so we need to dedup by keys.
dedup = stringset.New(0)
}
stopChan := make(chan struct{})
parIter := queryToIter(stopChan, toRun, parentDS)
memIter := queryToIter(stopChan, toRun, memDS)
parItemGet := func() (*item, error) {
for {
itm, err := parIter()
if itm == nil || err != nil {
return nil, err
}
encKey := itm.getEncKey()
if sizes.has(encKey) || (dedup != nil && dedup.Has(encKey)) {
continue
}
return itm, nil
}
}
memItemGet := func() (*item, error) {
for {
itm, err := memIter()
if itm == nil || err != nil {
return nil, err
}
if dedup != nil && dedup.Has(itm.getEncKey()) {
continue
}
return itm, nil
}
}
defer func() {
close(stopChan)
parItemGet()
memItemGet()
}()
pitm, err := parItemGet()
if err != nil {
return err
}
mitm, err := memItemGet()
if err != nil {
return err
}
for {
// the err can be set during the loop below. If we come around the bend and
// it's set, then we need to return it. We don't check it immediately
// because it's set after we already have a good result to return to the
// user.
if err != nil {
return err
}
usePitm := pitm != nil
if pitm != nil && mitm != nil {
usePitm = cmpFn(pitm) < cmpFn(mitm)
} else if pitm == nil && mitm == nil {
break
}
toUse := (*item)(nil)
// we check the error at the beginning of the loop.
if usePitm {
toUse = pitm
pitm, err = parItemGet()
} else {
toUse = mitm
mitm, err = memItemGet()
}
if dedup != nil {
if !dedup.Add(toUse.getEncKey()) {
continue
}
}
if distinct != nil {
// NOTE: We know that toUse will not be used after this point for
// comparison purposes, so re-use its cmpRow property for our distinct
// filter here.
toUse.cmpRow = ""
if !distinct.Add(toUse.getCmpRow(nil, nil, distinctOrder)) {
continue
}
}
if err := cb(toUse.key, toUse.data); err != nil {
if err == ds.Stop {
return nil
}
return err
}
}
return nil
}