Swaminathan Balachandran created HDDS-14242:
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Summary: Make RDBStoreAbstractIterator set bounds in ReadOptions
for prefix based iteration
Key: HDDS-14242
URL: https://issues.apache.org/jira/browse/HDDS-14242
Project: Apache Ozone
Issue Type: Sub-task
Reporter: Swaminathan Balachandran
Assignee: Swaminathan Balachandran
Currently for prefix based iteration, the comparison happens on Java side which
is inefficient firstly because this incurs an additional buffer copy cost in
each and every call of hasNext on iteration i.e. in case of
RDBStoreCodecBufferIterator it is going to be a copy b/w 2 direct byte buffer
and in case of RDBStoreByteArrayIterator it is going to be a direct to heap
byte array allocation which is expensive.
Moreover the prefix check is also inefficient on java side and this would be
very efficient on c++ since rocksdb internally does a memcmp.
The patch aims to set lowerBound and upperBound in readOptions on rocksItr
initialize.
Here the lowerBound is going to be the prefix itself and upperBound is going to
be nextHigherByteArray entry. If the prefix is going to have all bytes start
with 0xFF or if it is empty then there can be no upper bound for the iterator
and lower bound is going to be just and the iteration has to happen beginning
from the prefix and iterate till the end of the table.
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