feat(mito): limit compaction output file size

[v0y4g3r]

I hereby agree to the terms of the GreptimeDB CLA.

Refer to a related PR or issue link (optional)

What's changed and what's your intention?

This PR adds a limit to the compaction output file size so that compaction will not generate a huge file which may slow down queries.

Now we can create tables with explicit output file limit:

CREATE TABLE monitor (
    host STRING,
    ts TimestampSecond DEFAULT CURRENT_TIMESTAMP() TIME INDEX,
    cpu FLOAT64 DEFAULT 0,
    memory FLOAT64,
    PRIMARY KEY(host)
) WITH (
    'append_mode'='true', 
    'compaction.type'='twcs', 
    'compaction.twcs.max_output_file_size'='1GB'
);

SST files distribution under TSBS workload (with max_output_file_size=128MB):

 # Before
-rw-rw-r-- 1 lei lei 135M Sep 20 16:38 32f86803-e73e-4ca2-a61e-68dc45b653e0.parquet
-rw-rw-r-- 1 lei lei  46M Sep 20 16:36 69539117-4acc-4f8f-9af2-e685c505c5b2.parquet
-rw-rw-r-- 1 lei lei  91M Sep 20 16:37 838dfa1c-1330-499d-8a15-5a0179ce801e.parquet
-rw-rw-r-- 1 lei lei  46M Sep 20 16:38 9cd89ebb-044a-450b-98e2-ab3ffa40e806.parquet
-rw-rw-r-- 1 lei lei 279M Sep 20 16:37 9d8e7106-62b5-4a72-ab4e-684a246fd326.parquet
-rw-rw-r-- 1 lei lei 273M Sep 20 16:35 af108633-fbc1-44f7-a352-7be08431cd97.parquet

# After
-rw-rw-r-- 1 lei lei  90M Sep 20 22:19 0e172b52-ebf8-4ac0-b1f3-34f17154295e.parquet
-rw-rw-r-- 1 lei lei  91M Sep 20 22:18 1f2ac123-f381-4cf6-b0f7-760f6ceda18a.parquet
-rw-rw-r-- 1 lei lei  90M Sep 20 22:19 3c47a5dd-c648-4b61-aa48-ae0f55bb8686.parquet
-rw-rw-r-- 1 lei lei  90M Sep 20 22:16 3e7b24dd-cfe3-4155-a268-5f2dba6d2bd3.parquet
-rw-rw-r-- 1 lei lei  90M Sep 20 22:19 4bbbcd26-fd9a-444b-b14d-db11e20b1350.parquet
-rw-rw-r-- 1 lei lei  90M Sep 20 22:17 8432536a-93e3-45fa-ab8f-f63ad1d90fa1.parquet
-rw-rw-r-- 1 lei lei  46M Sep 20 22:19 c66a2604-b076-4eec-b085-2a013f5ff6c0.parquet
-rw-rw-r-- 1 lei lei  91M Sep 20 22:16 cb2dbe3f-691b-4dc9-a877-7213282905b4.parquet
-rw-rw-r-- 1 lei lei  91M Sep 20 22:18 d5b72303-7fbe-4aef-904e-6e681b68f0bb.parquet
-rw-rw-r-- 1 lei lei  91M Sep 20 22:16 fa146609-2875-44f9-9a7c-094e968d5aa4.parquet

Caveats

Currently this policy only applies when either append mode is enabled or compacted inputs does not overlap with other inputs (so that we can reasobably estimate the ouput file size). For those overlapping files, we may need to examine row groups' statistic data to further calculate the output file size. But this is not oncluded in this patch.

Checklist

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR requires documentation updates.

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[codecov]

Codecov Report

Attention: Patch coverage is 86.66667% with 18 lines in your changes missing coverage. Please review.

Project coverage is 84.28%. Comparing base (163cea8) to head (2aa6d42).
Report is 12 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4754      +/-   ##
==========================================
- Coverage   84.67%   84.28%   -0.39%     
==========================================
  Files        1118     1117       -1     
  Lines      202454   202759     +305     
==========================================
- Hits       171429   170900     -529     
- Misses      31025    31859     +834     

[waynexia]

what happens if those params are in conflict and cannot all be met?

[evenyag]

We should allow a compaction task to generate multiple files to avoid outputting a huge file. So the task can finish writing the current output file and start a new output file. But this requires the compaction task itself to generate file ids.

[v0y4g3r]

what happens if those params are in conflict and cannot all be met?

max_output_file_size has higher priority than max_[in]active_window_files. For example, if max_[in]active_window_files allows at most 1 file per window, while the output file size exceedsmax_output_file_size, the output will be split.

[v0y4g3r]

We should allow a compaction task to generate multiple files to avoid outputting a huge file. So the task can finish writing the current output file and start a new output file. But this requires the compaction task itself to generate file ids.

This will not be included in this PR since it involves refactoring both WriteCache and ParquetWriter.

[waynexia]

It might also be beneficial to group small size inputs into a larger one while still keeping the total size under the threshold. But this PR looks fine to merge and we can do this in follow-up changes.