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https://issues.apache.org/jira/browse/HADOOP-9530?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Wei Yan updated HADOOP-9530:
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Attachment: HADOOP-9530.patch
[~jserdaru], we also run this problem. As you mentioned, Oracle sql is
different from MySQL which uses row offset. Uploaded a patch to fix this
problem.
> DBInputSplit creates invalid ranges on Oracle
> ---------------------------------------------
>
> Key: HADOOP-9530
> URL: https://issues.apache.org/jira/browse/HADOOP-9530
> Project: Hadoop Common
> Issue Type: Bug
> Affects Versions: 1.1.2
> Reporter: Julien Serdaru
> Attachments: HADOOP-9530.patch
>
>
> The DBInputFormat on Oracle does not create valid ranges.
> The method getSplit line 263 is as follows:
> split = new DBInputSplit(i * chunkSize, (i * chunkSize) +
> chunkSize);
> So the first split will have a start value of 0 (0*chunkSize).
> However, the OracleDBRecordReader, line 84 is as follows:
> if (split.getLength() > 0 && split.getStart() > 0){
> Since the start value of the first range is equal to 0, we will skip the
> block that partitions the input set. As a result, one of the map task will
> process the entire data set, rather than the partition.
> I'm assuming the fix is trivial and would involve removing the second check
> in the if block.
> Also, I believe the OracleDBRecordReader paging query is incorrect.
> Line 92 should read:
> query.append(" ) WHERE dbif_rno > ").append(split.getStart());
> instead of (note > instead of >=)
> query.append(" ) WHERE dbif_rno >= ").append(split.getStart());
> Otherwise some rows will be ignored and some counted more than once.
> A map/reduce job that counts the number of rows based on a predicate will
> highlight the incorrect behavior.
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