@@ -377,11 +377,20 @@ func (qs *queryState) handleValuePostings(ctx context.Context, args funcArgs) er
377377 outputs := make ([]* pb.Result , numGo )
378378 listType := schema .State ().IsList (q .Attr )
379379
380+ // These are certain special cases where we can get away with reading only the latest value
381+ // Lang doesn't work because we would be storing various different languages at various
382+ // time. So when we go to read the latest value, we might get a different language.
383+ // Similarly with DoCount and ExpandAll and Facets. List types are also not supported
384+ // because list is stored by time, and we combine all the list items at various timestamps.
385+ hasLang := schema .State ().HasLang (q .Attr )
386+ getMultiplePosting := q .DoCount || q .ExpandAll || listType || hasLang || q .FacetParam != nil
387+
380388 calculate := func (start , end int ) error {
381389 x .AssertTrue (start % width == 0 )
382390 out := & pb.Result {}
383391 outputs [start / width ] = out
384392
393+ cache := make ([]* pb.PostingList , 0 )
385394 for i := start ; i < end ; i ++ {
386395 select {
387396 case <- ctx .Done ():
@@ -391,49 +400,86 @@ func (qs *queryState) handleValuePostings(ctx context.Context, args funcArgs) er
391400 key := x .DataKey (q .Attr , q .UidList .Uids [i ])
392401
393402 // Get or create the posting list for an entity, attribute combination.
394- pl , err := qs .cache .Get (key )
395- if err != nil {
396- return err
397- }
398403
399- // If count is being requested, there is no need to populate value and facets matrix.
400- if q .DoCount {
401- count , err := countForValuePostings (args , pl , facetsTree , listType )
402- if err != nil && err != posting .ErrNoValue {
404+ var vals []types.Val
405+ fcs := & pb.FacetsList {FacetsList : make ([]* pb.Facets , 0 )} // TODO Figure out how it is stored
406+
407+ if ! getMultiplePosting {
408+ if len (cache ) == 0 {
409+ keys := make ([][]byte , 10 )
410+ keys [0 ] = key
411+ for j := i + 1 ; j < i + 10 && j < end ; j ++ {
412+ keys [j - i ] = x .DataKey (q .Attr , q .UidList .Uids [j ])
413+ }
414+ cache , err = qs .cache .GetBatchSinglePosting (keys )
415+ if err != nil {
416+ return err
417+ }
418+ }
419+ pl := cache [0 ]
420+ if len (cache ) > 1 {
421+ cache = cache [1 :]
422+ }
423+ if pl == nil || len (pl .Postings ) == 0 {
424+ out .UidMatrix = append (out .UidMatrix , & pb.List {})
425+ out .FacetMatrix = append (out .FacetMatrix , & pb.FacetsList {})
426+ out .ValueMatrix = append (out .ValueMatrix ,
427+ & pb.ValueList {Values : []* pb.TaskValue {}})
428+ continue
429+ }
430+ vals = make ([]types.Val , len (pl .Postings ))
431+ for i , p := range pl .Postings {
432+ vals [i ] = types.Val {
433+ Tid : types .TypeID (p .ValType ),
434+ Value : p .Value ,
435+ }
436+ }
437+ } else {
438+ pl , err := qs .cache .Get (key )
439+ if err != nil {
403440 return err
404441 }
405- out .Counts = append (out .Counts , uint32 (count ))
406- // Add an empty UID list to make later processing consistent.
407- out .UidMatrix = append (out .UidMatrix , & pb.List {})
408- continue
409- }
410442
411- vals , fcs , err := retrieveValuesAndFacets (args , pl , facetsTree , listType )
412- switch {
413- case err == posting .ErrNoValue || (err == nil && len (vals ) == 0 ):
414- // This branch is taken when the value does not exist in the pl or
415- // the number of values retrieved is zero (there could still be facets).
416- // We add empty lists to the UidMatrix, FaceMatrix, ValueMatrix and
417- // LangMatrix so that all these data structure have predictable layouts.
418- out .UidMatrix = append (out .UidMatrix , & pb.List {})
419- out .FacetMatrix = append (out .FacetMatrix , & pb.FacetsList {})
420- out .ValueMatrix = append (out .ValueMatrix ,
421- & pb.ValueList {Values : []* pb.TaskValue {}})
422- if q .ExpandAll {
423- // To keep the cardinality same as that of ValueMatrix.
424- out .LangMatrix = append (out .LangMatrix , & pb.LangList {})
443+ // If count is being requested, there is no need to populate value and facets matrix.
444+ if q .DoCount {
445+ count , err := countForValuePostings (args , pl , facetsTree , listType )
446+ if err != nil && err != posting .ErrNoValue {
447+ return err
448+ }
449+ out .Counts = append (out .Counts , uint32 (count ))
450+ // Add an empty UID list to make later processing consistent.
451+ out .UidMatrix = append (out .UidMatrix , & pb.List {})
452+ continue
425453 }
426- continue
427- case err != nil :
428- return err
429- }
430454
431- if q .ExpandAll {
432- langTags , err := pl .GetLangTags (args .q .ReadTs )
433- if err != nil {
455+ vals , fcs , err = retrieveValuesAndFacets (args , pl , facetsTree , listType )
456+
457+ switch {
458+ case err == posting .ErrNoValue || (err == nil && len (vals ) == 0 ):
459+ // This branch is taken when the value does not exist in the pl or
460+ // the number of values retrieved is zero (there could still be facets).
461+ // We add empty lists to the UidMatrix, FaceMatrix, ValueMatrix and
462+ // LangMatrix so that all these data structure have predictable layouts.
463+ out .UidMatrix = append (out .UidMatrix , & pb.List {})
464+ out .FacetMatrix = append (out .FacetMatrix , & pb.FacetsList {})
465+ out .ValueMatrix = append (out .ValueMatrix ,
466+ & pb.ValueList {Values : []* pb.TaskValue {}})
467+ if q .ExpandAll {
468+ // To keep the cardinality same as that of ValueMatrix.
469+ out .LangMatrix = append (out .LangMatrix , & pb.LangList {})
470+ }
471+ continue
472+ case err != nil :
434473 return err
435474 }
436- out .LangMatrix = append (out .LangMatrix , & pb.LangList {Lang : langTags })
475+
476+ if q .ExpandAll {
477+ langTags , err := pl .GetLangTags (args .q .ReadTs )
478+ if err != nil {
479+ return err
480+ }
481+ out .LangMatrix = append (out .LangMatrix , & pb.LangList {Lang : langTags })
482+ }
437483 }
438484
439485 uidList := new (pb.List )
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