Improve flat_object field parsing performance by reducing two passes to a single pass

[bugmakerrrrrr]

Description

As discussed in #16061, this PR focuses on optimizing flat_object type in a BWC way. I benchmarked this change using noaa workload and set the type of field station as flat_object, the result is as follows.

|                                                        Metric |                     Task |    Baseline |   Contender |     Diff |   Unit |
|--------------------------------------------------------------:|-------------------------:|------------:|------------:|---------:|-------:|
|                                                Min Throughput |                    index |      134517 |      133508 | -1008.98 | docs/s |
|                                               Mean Throughput |                    index |      142195 |      144423 |  2227.85 | docs/s |
|                                             Median Throughput |                    index |      143126 |      146146 |  3020.51 | docs/s |
|                                                Max Throughput |                    index |      150619 |      151649 |   1029.8 | docs/s |
|                                       50th percentile latency |                    index |     206.277 |     210.876 |  4.59914 |     ms |
|                                       90th percentile latency |                    index |     544.938 |     505.005 | -39.9333 |     ms |
|                                       99th percentile latency |                    index |     1225.61 |     1162.57 | -63.0459 |     ms |
|                                     99.9th percentile latency |                    index |     1867.85 |     1568.05 | -299.801 |     ms |
|                                      100th percentile latency |                    index |     1892.49 |     1759.06 |  -133.43 |     ms |
|                                  50th percentile service time |                    index |     206.277 |     210.876 |  4.59914 |     ms |
|                                  90th percentile service time |                    index |     544.938 |     505.005 | -39.9333 |     ms |
|                                  99th percentile service time |                    index |     1225.61 |     1162.57 | -63.0459 |     ms |
|                                99.9th percentile service time |                    index |     1867.85 |     1568.05 | -299.801 |     ms |
|                                 100th percentile service time |                    index |     1892.49 |     1759.06 |  -133.43 |     ms |
|                                                    error rate |                    index |           0 |           0 |        0 |      % |

Related Issues

Resolves #[Issue number to be closed when this PR is merged]

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

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[github-actions]

❌ Gradle check result for 5d37267: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions]

✅ Gradle check result for 5dccc88: SUCCESS

[codecov]

Codecov Report

Attention: Patch coverage is 78.01418% with 31 lines in your changes missing coverage. Please review.

Project coverage is 72.37%. Comparing base (6b1861a) to head (fa569aa).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
...opensearch/index/mapper/FlatObjectFieldMapper.java	78.01%	13 Missing and 18 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #16297      +/-   ##
============================================
+ Coverage     72.23%   72.37%   +0.13%     
- Complexity    65335    65414      +79     
============================================
  Files          5301     5301              
  Lines        303824   303769      -55     
  Branches      44033    44033              
============================================
+ Hits         219471   219856     +385     
+ Misses        66363    65874     -489     
- Partials      17990    18039      +49     

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[bugmakerrrrrr]

@msfroh @kkewwei please take a look when you get a chance

[opensearch-trigger-bot]

This PR is stalled because it has been open for 30 days with no activity.

[bugmakerrrrrr]

❌ Gradle check result for 92f1f05: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

The current implementation of the range query is incorrect. When either the upper term or lower term is null, the range query combines the prefix with the literal value of null for searching.

[github-actions]

❌ Gradle check result for dca3469: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[bugmakerrrrrr]

@msfroh @kkewwei friendly ping :)

[msfroh]

Overall, I really like the cleanup with this change!

I was never a big fan of the JsonToStringXContentParser, so I'm happy to see it go away.

[github-actions]

✅ Gradle check result for abb44a1: SUCCESS

[github-actions]

❌ Gradle check result for 6afc5b2: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[msfroh]

I'm happy with these changes. Thanks a lot, @bugmakerrrrrr!

Would you mind resolving the merge conflicts and we can get this in?

@kkewwei -- do you have any more comments/concerns?

[kkewwei]

I'm happy with these changes. Thanks a lot, @bugmakerrrrrr!

Would you mind resolving the merge conflicts and we can get this in?

@kkewwei -- do you have any more comments/concerns?

It also make sense to me.

[bugmakerrrrrr]

Would you mind resolving the merge conflicts and we can get this in?

@msfroh done

[github-actions]

✅ Gradle check result for 7d1aff1: SUCCESS

[github-actions]

✅ Gradle check result for 013c81b: SUCCESS

[bugmakerrrrrr]

hi @msfroh , can we merge this? After this is merged, I'll continue the work mentioned in #16061

[github-actions]

✅ Gradle check result for fa569aa: SUCCESS

[opensearch-trigger-bot]

The backport to 2.x failed:

The process '/usr/bin/git' failed with exit code 128

To backport manually, run these commands in your terminal:

# Navigate to the root of your repository
cd $(git rev-parse --show-toplevel)
# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add ../.worktrees/OpenSearch/backport-2.x 2.x
# Navigate to the new working tree
pushd ../.worktrees/OpenSearch/backport-2.x
# Create a new branch
git switch --create backport/backport-16297-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 27946550b686df41fd0ff53cb340ce52c73a7b45
# Push it to GitHub
git push --set-upstream origin backport/backport-16297-to-2.x
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/OpenSearch/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-16297-to-2.x.