GitHub user ravipesala opened a pull request:
https://github.com/apache/carbondata/pull/1436
[WIP][CARBONDATA-1617] Merging carbonindex files within segment
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Problem :
The first-time query of carbon becomes very slow. It is because of reading
many small carbonindex files and cache to the driver at the first time.
Many carbonindex files are created in below case
Loading data in large cluster
For example, if the cluster size is 100 nodes then for each load 100 index
files are created per segment. So after 100 loads, the number of carbonindex
files becomes 10000. .
It will be slower to read all the files from the driver since a lot of
namenode calls and IO operations.
Solution :
Merge the carbonindex files in two levels.so that we can reduce the IO
calls to namenode and improves the read performance.
Merge within a segment.
Merge the carbonindex files to single file immediately after load completes
within the segment. It would be named as a .carbonindexmerge file. It is
actually not a true data merging but a simple file merge. So that the current
structure of carbonindex files does not change. While reading we just read one
file instead of many carbonindex files within the segment.
- [ ] Any interfaces changed?
- [ ] Any backward compatibility impacted?
- [ ] Document update required?
- [ ] Testing done
Please provide details on
- Whether new unit test cases have been added or why no new tests
are required?
- How it is tested? Please attach test report.
- Is it a performance related change? Please attach the performance
test report.
- Any additional information to help reviewers in testing this
change.
- [ ] For large changes, please consider breaking it into sub-tasks under
an umbrella JIRA.
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You can merge this pull request into a Git repository by running:
$ git pull https://github.com/ravipesala/incubator-carbondata
carbon-index-merge
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/carbondata/pull/1436.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #1436
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commit bbabb705b8dc81a6569b66ee3bb1765de04348c7
Author: ravipesala <[email protected]>
Date: 2017-10-25T05:43:22Z
Merging carbonindex files within segment
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