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From Biplob Biswas <revolutioni...@gmail.com>
Subject difference - filterlist with rowfilters vs multiget
Date Wed, 15 Aug 2018 09:06:29 GMT
Hi,

During our implementation for fetching multiple records from an HBase
table, we came across a discussion regarding the best way to get records
out.

The first implementation is something like:

          FilterList filterList = new FilterList(Operator.MUST_PASS_ONE);
>           for (String rowKey : rowKeys) {
>             filterList.addFilter(new RowFilter(CompareOp.EQUAL,new
> BinaryComparator(Bytes.toBytes(rowKey))));
>           }
>
>   Scan scan = new Scan();
>   scan.setFilter(filterList);
>   ResultScanner resultScanner = table.getScanner(scan);


and the second implementation is somethign like this:

         List<Get> listGet = rowKeys.stream()
>               .map(entry -> {
>                 Get get = new Get(Bytes.toBytes(entry));
>                 return get;
>               })
>               .collect(Collectors.toList());
>   Result[] results = table.get(listGet)


The only difference I see directly is that filterList would do a full table
scan whereas multiget wouldn't do anything as such.

But what other benefits one has over the other? Also, when HBase finds out
that all the filters in the filterList are RowFilters, would it perform
some kind of optimization and perform multiget rather than doing a full
table scan?


Thanks & Regards
Biplob Biswas

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