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https://issues.apache.org/jira/browse/ACCUMULO-403?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Keith Turner updated ACCUMULO-403:
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Fix Version/s: (was: 1.5.0)
1.4.1
> Create general row selection iterator
> -------------------------------------
>
> Key: ACCUMULO-403
> URL: https://issues.apache.org/jira/browse/ACCUMULO-403
> Project: Accumulo
> Issue Type: New Feature
> Components: client, tserver
> Reporter: Keith Turner
> Assignee: Billie Rinaldi
> Fix For: 1.4.1
>
>
> The WholeRowIterator support filtering rows that meet a certain criteria.
> However it reads the entire row into memory. It is possible to efficiently
> select rows w/o reading them into memory by using two iterators. One
> iterator for selection, one for reading. When its determined that a row is
> not needed using the selection iterator, then seek the read iterator over the
> row.
> This pattern could be made into an easy to use iterator that users extend.
> The iterator could have an abstract method that user implement to decide if
> they want to select or filter a row. Could look something like the following.
> {noformat}
> class RowSelectionIterator extends WrappingIterator {
> public abstract boolean selectRow(SortedKeyValueIterator row);
> }
> {noformat}
> Below is a simple example of a row selection iterator that returns rows that
> have the columns foo and bar.
> {noformat}
> class FooBarRowSelector extends RowSelectionIterator {
> public boolean selectRow(SortedKeyValueIterator row){
>
> Text row = row.getTopKey().getRow();
> //seek instead of scanning, this more efficient for large rows w/ lots
> of columns...
> //if the row only has a few columns scanning is probably faster... also
> seeking the
> //columns in sorted order is more efficient.
> row.seek(Range.exact(row, 'bar');
> boolean sawBar = row.hasTop();
> if(!sawBar)
> return false;
> row.seek(Range.exact(row, 'foo'));
> boolean sawFoo = row.hasTop();
> return sawFoo;
> }
> }
> {noformat}
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