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https://issues.apache.org/jira/browse/HBASE-4612?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13130020#comment-13130020
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Eran Kutner commented on HBASE-4612:
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Hi Jonathan, thanks for the feedback! See answers inline:
{quote}There's no explanation of the behavior anywhere. In the constructors and
addPrefix() methods, you should document that this creates an OR condition
across all of the prefixes, correct?{quote} - good point, added some more
explanations.
{quote}No need to instantiate a new comparator all the time (use
Bytes.BYTES_COMPARATOR){quote} - Didn't know it existed. Changed.
{quote}Something seems odd when you keep adding to the end of a List and then
sort. How about a TreeSet? You can easily ignore dupes that way.{quote} - This
is intentional. Sorting is done only during initialization but accessing a
ArrayList, which is actually based on an array, is much more efficient than
accessing a tree, so I sacrifice the aesthetics of the code for better runtime
performance.
{quote}There's no input verification so, for example, you could pass a null to
the constructor or an empty byte[][] and have some strange behavior. Like it
will instantiate okay but then you'll get server-side NPEs or IOOB.{quote} -
it's a good point but I've looked and no other filter is validating its input
either. I can throw a InvalidArgumentException but don't know if it's a good
idea considering it's not the norm.
{quote}this.prefixes.size() == 0 -> this.prefixes.isEmpty(){quote} - ok,
changed.
{quote}your comment at the top of filterColumn, i wouldn't exactly call it a
workaround, but it's a good comment. looking at the logic, it seems like
correct behavior would be that it can be called with current == size() but it
would be a bug if current > size(), right? should you add an assert or throw an
exception?{quote} - well it is kind of a workaround, because as an individual
filter I expect not be called again after returning NEXT_ROW, however, when
used with FilterList the filter does get called again which puts it in an
ilegal state, so it has to explicitly handle that case. That is also why it
can't throw an exception in that scenario, because it seems to be happening
normally when used with FilterList. as for "current" it has to be smaller than
size() or it would be outside the bounds of the array.
> Allow ColumnPrefixFilter to support multiple prefixes
> -----------------------------------------------------
>
> Key: HBASE-4612
> URL: https://issues.apache.org/jira/browse/HBASE-4612
> Project: HBase
> Issue Type: Improvement
> Components: filters
> Affects Versions: 0.90.4
> Reporter: Eran Kutner
> Assignee: Eran Kutner
> Priority: Minor
> Fix For: 0.94.0
>
> Attachments: HBASE-4612-0.90.patch
>
>
> When having a lot of columns grouped by name I've found that it would be very
> useful to be able to scan them using multiple prefixes, allowing to fetch
> specific groups in one scan, without fetching the entire row. This is
> impossible to achieve using a FilterList, so I've added such support to the
> existing ColmnPrefixFilter while keeping backward compatibility.
> The attached patch is based on 0.90.4, I noticed that the 0.92 branch has a
> new method to support instantiating filters using Thrift. I'm not sure how
> the serialization works there so I didn't implement that, but the rest of my
> code should work in 0.92 as well.
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