[MINOR][DOCS] Fix typos in sql-ref-datatypes.md

[kariya-mitsuru]

What changes were proposed in this pull request?

Fixing typos in the docs sql-ref-datatypes.md.

Why are the changes needed?

To display '<element_type>' correctly.

Does this PR introduce any user-facing change?

No.

How was this patch tested?

Manually run jekyll.

before this fix

after this fix

[kiszk]

Could you please attach screen captures in the description if possible?

[kariya-mitsuru]

Could you please attach screen captures in the description if possible?

I have attached screen captures of before and after this fix.

[HyukjinKwon]

ok to test

[HyukjinKwon]

Interesting .. why do we have to escape this alone?
Looks good anyway as it works ..

[HyukjinKwon]

Oh, it thinks it's an HTML.

[kiszk]

I am also curious about why STRUCT and Map do not require escape.

[kariya-mitsuru]

This behavior comes from kramdown which is used by Jekyll.

The element_type is interpreted as an html tag because it consists of only alphabet characters.
On the other hand, field1_name: field1_type, field2_name: field2_type, ...(STRUCT) and key_type, value_type(MAP) contain bare comma, so they cannot be interpreted as html tags.

Strictly speaking, kramdown uses the following regular expression to determine whether it is an html tag or not.

(?m-ix:<((?>(?:[[:alpha:]_][-[:alnum:]._]*:)?[[:alpha:]_][-[:alnum:]._]*))\\s*((?>\\s+(?:[[:alpha:]_][-[:alnum:]._]*:)?[[:alpha:]_][-[:alnum:]._]*(?:\\s*=\\s*(?:\\p{Word}+|(\"|').*?\\3))?)*)\\s*(\\/)?>)

[SparkQA]

Test build #134179 has finished for PR 31221 at commit 3b4698a.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[HyukjinKwon]

Let me merge this one anyway. It looks good and approved by @kiszk and me but it would be great if we can know why (#31221 (comment)).

[HyukjinKwon]

Merged to master, branch-3.1 and branch-3.0.

[SparkQA]

Kubernetes integration test starting
URL: https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder-K8s/38763/

[SparkQA]

Kubernetes integration test status success
URL: https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder-K8s/38763/