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From "Bharath Vissapragada (Code Review)" <>
Subject [Impala-ASF-CR] IMPALA-4840: Fix REFRESH performance regression.
Date Wed, 15 Feb 2017 20:27:52 GMT
Bharath Vissapragada has uploaded a new patch set (#3).

Change subject: IMPALA-4840: Fix REFRESH performance regression.

IMPALA-4840: Fix REFRESH performance regression.

The fix for IMPALA-4172 introduced a regression in
performance of the REFRESH command. The regression
stems from the fact that we reload the block metadata
of every valid data file without considering whether it
has changed since the last load. This caused unnecessary
metadata loads for unchanged files and thus increasing
the runtime.

The fix involves having the refresh codepath (and other
operations that use the same codepath like insert etc.) to
reload the metadata of only modified files by doing a
listStatus() on the partition directory and checking the
last modified time of each file. Without this patch, we relied
on listFiles(), which fetched the block locations irrespective of
whether the file has changed and it was significantly slower on
unchanged tables. The initial/invalidate metadata load still
fetches the block locations in bulk using listFiles(). The
side effect of this change is that the refresh no longer picks up
block location changes after HDFS block rebalancing. We suggest
using "invalidate metadata" for that which loads the metadata from

Additionally, this commit enables the reuse of metadata during
table refresh (which was disabled in IMPALA-4172) to prevent
reloading metadata from HMS everytime.

Change-Id: I859b9fe93563ba886d0b5db6db42a14c88caada8
M fe/src/main/java/org/apache/impala/catalog/
M fe/src/main/java/org/apache/impala/catalog/
2 files changed, 110 insertions(+), 32 deletions(-)

  git pull ssh:// refs/changes/09/6009/3
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Gerrit-MessageType: newpatchset
Gerrit-Change-Id: I859b9fe93563ba886d0b5db6db42a14c88caada8
Gerrit-PatchSet: 3
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Bharath Vissapragada <>
Gerrit-Reviewer: Alex Behm <>
Gerrit-Reviewer: Bharath Vissapragada <>
Gerrit-Reviewer: Dimitris Tsirogiannis <>

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