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Add a comment about limitsHint.

This commit is contained in:
A.J. Beamon 2022-03-08 14:35:22 -08:00
parent 36435af4f5
commit d71e91eea5
1 changed files with 13 additions and 0 deletions
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13
fdbclient/SpecialKeySpace.actor.h
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@ -36,6 +36,19 @@
class SpecialKeyRangeReadImpl {
public:
// Each derived class only needs to implement this simple version of getRange
//
// limitsHint can be used to reduce the amount of reading that the underlying
// implementation needs to do.
//
// NOTE: care needs to be taken when using limitsHint. If the range in question
// supports it, it is possible that some of the results may be removed when
// merged with mutations from the same transaction. If that happens, the final
// result may have fewer elements than the limit or even none at all if you didn't
// read the entire range.
//
// TODO: implement the range reading in a loop so that the underlying implementation
// can more naively fetch items up to the limit. If the merging deletes any entries,
// then the next set of entries can be read.
virtual Future<RangeResult> getRange(ReadYourWritesTransaction* ryw,
KeyRangeRef kr,
GetRangeLimits limitsHint) const = 0;