functions-and-operators: enrich instructions for string functions CHAR_LENGTH() and CHARACTER_LENGTH #15483

[PitifulPete]

What is changed, added or deleted? (Required)

• Fix (Enrich instructions for string functions CHAR_LENGTH() and CHARACTER_LENGTH() #15483)
• Describe the CHAR_LENGTH() and CHARACTER_LENGTH() functions
• Add two examples that illustrate how CHAR_LENGTH() works
• Add a blockquote under the second CHAR_LENGTH() example to indicate that the example operates under the assumption that a SQL database exist

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What is the related PR or file link(s)?

pingcap/tiflow#10197
pingcap/tiflow#10307

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Do your changes match any of the following descriptions?

• Delete files
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• Need modification after applied to another branch
• Might cause conflicts after applied to another branch

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[dveeden]

Maybe include a name where CHAR_LENGTH() and LENGTH() don't match:

mysql> WITH n AS (
    -> SELECT 'François Englert' AS p
    -> UNION ALL SELECT 'Albert Einstein'
    -> UNION ALL SELECT 'Robert Oppenheimer'
    -> )
    -> SELECT p, CHAR_LENGTH(p), LENGTH(p) FROM n;
+--------------------+----------------+-----------+
| p                  | CHAR_LENGTH(p) | LENGTH(p) |
+--------------------+----------------+-----------+
| François Englert   |             16 |        17 |
| Albert Einstein    |             15 |        15 |
| Robert Oppenheimer |             18 |        18 |
+--------------------+----------------+-----------+
3 rows in set (0.00 sec)

[PitifulPete]

I think this should be introduced in the LENGTH() subheading where the difference between LENGTH() and CHAR_LENGTH() will be stated and this type of example will be included. Adding it here when LENGTH() is yet to be introduced to the readers can confuse.

[dveeden]

Note that this PR might have some relation and/or overlap with #16068

[dveeden]

From the linter:

[2024-01-09T23:31:58.375Z] + markdownlint functions-and-operators/string-functions.md
[2024-01-09T23:31:58.375Z] functions-and-operators/string-functions.md: 139: MD031/blanks-around-fences Fenced code blocks should be surrounded by blank lines [Context: "```"]

[yibin87]

Others LGTM

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[PitifulPete]

@qiancai, could you merge commits unrelated to this issue with their respective branches?

[dveeden]

@qiancai, could you merge commits unrelated to this issue with their respective branches?

I think it might be good to do an interactive rebase to pick the right commits.

1. Make sure you're on the right branch: git checkout enrich/instructions-string-functions
2. Make sure git is up to date: git fetch --all
3. Now start the rebase git rebase -i upstream/master
   a. This assumes there is a "remote" with the name upstream. You can check the output of git remote -v to check what removes are available.

The rebase should look like this:

For each line you can:

• Remove the line to remove that commit from the PR
• Change the word pick into fixup to merge commits together (probably not needed here)
• More options are in the help text, but probably also not needed.

See also https://git-scm.com/book/en/v2/Git-Tools-Rewriting-History

Once you save and exit the editor there might be conflicts. If this is the case then edit the file to fix the conflict and use git add to mark the file as done and hen do a git rebase --continue. This is also in the help text, for example:

$ git rebase -i upstream/master
Auto-merging functions-and-operators/string-functions.md
CONFLICT (content): Merge conflict in functions-and-operators/string-functions.md
error: could not apply 292a75611f... functions-and-operators: enrich instructions for string functions CHAR_LENGTH() and CHARACTER_LENGTH()
hint: Resolve all conflicts manually, mark them as resolved with
hint: "git add/rm <conflicted_files>", then run "git rebase --continue".
hint: You can instead skip this commit: run "git rebase --skip".
hint: To abort and get back to the state before "git rebase", run "git rebase --abort".
Could not apply 292a75611f... functions-and-operators: enrich instructions for string functions CHAR_LENGTH() and CHARACTER_LENGTH()

Once the rebase is done you would have to do a git push --force as you need to overwrite what's on GitHub. You can use tools like git log, git log --oneline upstream/master..HEAD and git diff upstream/master to verify everything is correct before you do this. If you want you can also do a git push -v --dry-run first.

[yibin87]

LGTM

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In response to this:

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-01-10 09:00:42.159045273 +0000 UTC m=+433831.743298962: ☑️ agreed by dveeden.
• 2024-01-30 01:48:17.100795781 +0000 UTC m=+1443738.665093486: ☑️ agreed by qiancai.

[qiancai]

/retest

[qiancai]

/approve

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: qiancai

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