Hadoop tables: If the version matches, do not reload metadata.

[rdblue]

#695 had a test failure because a Hadoop table had out of date metadata, even though there were no commits. The problem is that metadata is loaded into a new TableMetadata object each time refresh is called, even if it was already loaded and is still current. This adds a check when the current version is determined to avoid unnecessary reloads.

[prodeezy]

nice catch! 2 failures that seem related:

org.apache.iceberg.hadoop.TestHadoopCommits > testRenameThrow FAILED
    org.apache.iceberg.exceptions.ValidationException at TestHadoopCommits.java:360
org.apache.iceberg.hadoop.TestHadoopCommits > testRenameReturnFalse FAILED
    org.apache.iceberg.exceptions.ValidationException at TestHadoopCommits.java:360

[aokolnychyi]

LGTM as we have similar logic for Hive tables. Test failures seem relevant. @rdblue, could you check?

[rdblue]

Test failures had two causes. First, shouldRefresh wasn't reset correctly. Second, use of a spy prevented the table from loading the correct metadata because the mocked FS wasn't returning correct results. The test only worked in the first place because of this bug, which would reload v1 metadata as a different object so the operations would attempt to commit and trigger the injected failure.

[rdblue]

Looks like style check failed:

[ant:checkstyle] [ERROR] /home/travis/build/apache/incubator-iceberg/core/src/test/java/org/apache/iceberg/hadoop/TestHadoopCommits.java:29:8: Unused import - org.apache.hadoop.conf.Configuration. [UnusedImports]

[ant:checkstyle] [ERROR] /home/travis/build/apache/incubator-iceberg/core/src/test/java/org/apache/iceberg/hadoop/TestHadoopCommits.java:31:8: Unused import - org.apache.hadoop.fs.Path. [UnusedImports]

[ant:checkstyle] [ERROR] /home/travis/build/apache/incubator-iceberg/core/src/test/java/org/apache/iceberg/hadoop/TestHadoopCommits.java:56:15: Unused import - org.mockito.Mockito.spy. [UnusedImports]

[aokolnychyi]

+1

[aokolnychyi]

Thanks, @rdblue!