executor,infoschema: Add pad_attribute to collation info | tidb-test=pr/2354

[dveeden]

What problem does this PR solve?

Issue Number: close #54250

Problem Summary:

What changed and how does it work?

Check List

Tests

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

  • [ ] I checked and no code files have been changed.

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.

A `pad_attribute` column has been included in the `information_schema.collations` table and in the output of `SHOW COLLATION` to improve MySQL compatibility.

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[dveeden]

/ok-to-test

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Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 57.0857%. Comparing base (184b010) to head (49e4f77). Report is 115 commits behind head on master.

Additional details and impacted files

@@                Coverage Diff                @@
##             master     #54282         +/-   ##
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- Coverage   74.7619%   57.0857%   -17.6762%     
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  Files          1523       1672        +149     
  Lines        361410     628800     +267390     
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+ Hits         270197     358955      +88758     
- Misses        71584     246260     +174676     
- Partials      19629      23585       +3956     

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Components	Coverage Δ
dumpling	52.9656% <ø> (-2.2339%)	:arrow_down:
parser	∅ <ø> (∅)
br	52.7049% <ø> (+4.7412%)	:arrow_up:

[dveeden]

/test mysql-test

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/test mysql-test

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[dveeden]

/retest

[kennytm]

Sortlen in MySQL is defined as "related to the amount of memory required to sort strings expressed in the character set", but the meaning of the value is never explained. According to https://dba.stackexchange.com/questions/281360/whats-sortlen-of-mysql-collation

After 20 years of using MySQL, I have found no end-user use for Sortlen. Ignore it.

If we need to copy the result exactly from MySQL then many of the filled in sortlen are wrongly set to 1 in this PR:

mysql> select any_value(collation_name), sortlen, count(*) from information_schema.collations group by sortlen;
+---------------------------+---------+----------+
| any_value(collation_name) | sortlen | count(*) |
+---------------------------+---------+----------+
| armscii8_general_ci       |       1 |       98 |
| cp1250_czech_cs           |       2 |        3 |
| gb18030_unicode_520_ci    |       8 |      121 |
| latin2_czech_cs           |       4 |        2 |
| utf8mb4_0900_ai_ci        |       0 |       61 |
| utf8mb4_ja_0900_as_cs_ks  |      24 |        1 |
+---------------------------+---------+----------+
6 rows in set (0.02 sec)

OTOH if we accept sortlen is meaningless then keeping them as 1 should be good enough.

[dveeden]

I adjusted the sortlen for the collations in the new framework only and kept the rest to 1 as previously reported by show collations.

Don't think it is used anywhere.

[D3Hunter]

@hawkingrei @lcwangchao

[ti-chi-bot[bot]]

[LGTM Timeline notifier]

Timeline:

• 2024-07-09 16:04:22.240637097 +0000 UTC m=+373559.475871211: :ballot_box_with_check: agreed by tiancaiamao.
• 2024-07-10 07:11:58.047769831 +0000 UTC m=+428015.283003944: :ballot_box_with_check: agreed by hawkingrei.

[ti-chi-bot[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hawkingrei, tangenta, tiancaiamao

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Needs approval from an approver in each of these files:

• ~~OWNERS~~ [hawkingrei,tangenta,tiancaiamao]
• ~~pkg/infoschema/OWNERS~~ [tangenta]
• ~~pkg/parser/OWNERS~~ [tangenta]
• ~~pkg/planner/OWNERS~~ [hawkingrei]

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[hawkingrei]

/retest

[dveeden]

/retest