importer: sample a portion of compressed files to speed up import spec generation

[joechenrh]

What problem does this PR solve?

Issue Number: close #64770

Problem Summary:

What changed and how does it work?

For compressed files, it may be time consuming to get compression ratio for each file. Since the ratio we got is also a rough value, here we only sample first 512 (maybe make it configurable) files for each compression type and use harmonic mean to get the average compression ratio.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No need to test

  • I checked and no code files have been changed.

Create 10,000 zstd files on ks3, and import with a 8C instance.

Before:

mysql> import into test.t1 from "s3://global-sort/joechenrh/zstd/*.csv.zst?access-key=xxxxxx&secret-access-key=xxxxxx&endpoint=xxxxxx&force-path-style=false&region=Beijing&provider=ks" with thread=8, detached;
+--------+-----------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------+----------+-------+---------+------------------+---------------+----------------+----------------------------+------------+----------+------------+------------------+----------+-------------------------+---------------------+-----------------------+----------------+--------------+
| Job_ID | Group_Key | Data_Source                                                                                                                                                                             | Target_Table | Table_ID | Phase | Status  | Source_File_Size | Imported_Rows | Result_Message | Create_Time                | Start_Time | End_Time | Created_By | Last_Update_Time | Cur_Step | Cur_Step_Processed_Size | Cur_Step_Total_Size | Cur_Step_Progress_Pct | Cur_Step_Speed | Cur_Step_ETA |
+--------+-----------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------+----------+-------+---------+------------------+---------------+----------------+----------------------------+------------+----------+------------+------------------+----------+-------------------------+---------------------+-----------------------+----------------+--------------+
|      1 | NULL      | s3://global-sort/joechenrh/zstd/*.csv.zst?access-key=xxxxxx&endpoint=xxxxxx&force-path-style=false&provider=ks&region=Beijing&secret-access-key=xxxxxx | `test`.`t1`  |      114 |       | pending | 35.98GiB         |          NULL |                | 2025-12-10 05:43:08.049237 | NULL       | NULL     | root@%     | NULL             | NULL     | NULL                    | NULL                | NULL                  | NULL           | NULL         |
+--------+-----------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------+----------+-------+---------+------------------+---------------+----------------+----------------------------+------------+----------+------------+------------------+----------+-------------------------+---------------------+-----------------------+----------------+--------------+
1 row in set (3 min 9.709 sec)

After:

mysql> import into test.t1 from "s3://global-sort/joechenrh/zstd/*.csv.zst?access-key=xxxxxx&secret-access-key=xxxxxx&endpoint=xxxxxx&force-path-style=false&region=Beijing&provider=ks" with thread=8, detached;
+--------+-----------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------+----------+-------+---------+------------------+---------------+----------------+----------------------------+------------+----------+------------+------------------+----------+-------------------------+---------------------+-----------------------+----------------+--------------+
| Job_ID | Group_Key | Data_Source                                                                                                                                                                             | Target_Table | Table_ID | Phase | Status  | Source_File_Size | Imported_Rows | Result_Message | Create_Time                | Start_Time | End_Time | Created_By | Last_Update_Time | Cur_Step | Cur_Step_Processed_Size | Cur_Step_Total_Size | Cur_Step_Progress_Pct | Cur_Step_Speed | Cur_Step_ETA |
+--------+-----------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------+----------+-------+---------+------------------+---------------+----------------+----------------------------+------------+----------+------------+------------------+----------+-------------------------+---------------------+-----------------------+----------------+--------------+
|      1 | NULL      | s3://global-sort/joechenrh/zstd/*.csv.zst?access-key=xxxxxx&endpoint=xxxxxx&force-path-style=false&provider=ks&region=Beijing&secret-access-key=xxxxxx | `test`.`t1`  |      114 |       | pending | 35.98GiB         |          NULL |                | 2025-12-10 05:43:08.049237 | NULL       | NULL     | root@%     | NULL             | NULL     | NULL                    | NULL                | NULL                  | NULL           | NULL         |
+--------+-----------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------+----------+-------+---------+------------------+---------------+----------------+----------------------------+------------+----------+------------+------------------+----------+-------------------------+---------------------+-----------------------+----------------+--------------+
1 row in set (11.757 sec)

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[tiprow]

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[codecov]

Codecov Report

❌ Patch coverage is 46.26866% with 36 lines in your changes missing coverage. Please review.
✅ Project coverage is 68.6468%. Comparing base (b5e9bbc) to head (5bb4166).
⚠️ Report is 55 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #64769        +/-   ##
================================================
- Coverage   74.7349%   68.6468%   -6.0881%     
================================================
  Files          1889       1867        -22     
  Lines        515296     515259        -37     
================================================
- Hits         385106     353709     -31397     
- Misses       106380     139119     +32739     
+ Partials      23810      22431      -1379     

Flag	Coverage Δ
integration	41.6228% <0.0000%> (-6.5409%)	⬇️
unit	66.0241% <46.2686%> (-6.2787%)	⬇️

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Components	Coverage Δ
dumpling	52.8700% <ø> (ø)
parser	∅ <ø> (∅)
br	38.2999% <ø> (-24.8844%)	⬇️

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[D3Hunter]

maybe add a manual test for many number of GZ files, to see how much it can speed up the precheck part

[joechenrh]

/hold
Wait manual test

[joechenrh]

/unhold
Manual test result updated

[D3Hunter]

/retest

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[GMHDBJD]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: D3Hunter, GMHDBJD

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-12-05 07:54:15.799114322 +0000 UTC m=+595600.612891894: ☑️ agreed by D3Hunter.
• 2025-12-11 04:21:51.46442842 +0000 UTC m=+1101256.278205992: ☑️ agreed by GMHDBJD.

[tiprow]

@joechenrh: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

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[joechenrh]

/retest

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[joechenrh]

/retest

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[joechenrh]

/retest

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[D3Hunter]

/cherry-pick release-nextgen-20251011

[ti-chi-bot]

@D3Hunter: new pull request created to branch release-nextgen-20251011: #67654.
But this PR has conflicts, please resolve them!

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/cherry-pick release-nextgen-20251011

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