[SPARK-48584][SQL] Perf improvement for unescapePathName

[yaooqinn]

What changes were proposed in this pull request?

This PR improves perf for unescapePathName with algorithms briefly described as:

• If a path contains no '%' or contains '%' at position > path.length-2, we return the original identity instead of creating a new StringBuilder to append char by char
• Otherwise, we loop with 2 indices, plaintextStartIdx which starts from 0 and then points to the next char after resolving %xx, and plaintextEndIdx which points to the next '%'. plaintextStartIdx moves to plaintextEndIdx + 3 if %xx is valid, or moves to plaintextEndIdx + 1 if %xx is invalid.
• Instead of using Integer.parseInt with error capture, we identify the high and low characters manually.

Why are the changes needed?

performance improvement for hotspots

Does this PR introduce any user-facing change?

no

How was this patch tested?

• new tests in ExternalCatalogUtilsSuite
• Benchmark results (9-11x faster)

Was this patch authored or co-authored using generative AI tooling?

no

[yaooqinn]

cc @dongjoon-hyun @cloud-fan @LuciferYang @JoshRosen thanks

[beliefer]

Could you provide some micro benchmark?

[yaooqinn]

Could you provide some micro benchmark?

What do you mean by some micro benchmark? Are sql/catalyst/benchmarks/EscapePathBenchmark-results.txt and sql/catalyst/benchmarks/EscapePathBenchmark-jdk21-results.txt not sufficient ?

[beliefer]

Oh, I see.

[LuciferYang]

It seems that there is a typo in the pr description:

Instead of using Integer.parseInt with error capture, we identify the high and low chararaters manually.

chararaters -> characters

[yaooqinn]

Thank you @LuciferYang

[LuciferYang]

+1, LGTM
Thanks @yaooqinn

[beliefer]

How about if (plaintextEndIdx == -1 || plaintextEndIdx + 2 > path.length || path.lastIndexOf('%') == 0) ?

[yaooqinn]

|| path.lastIndexOf('%')

I'm sorry, I'm having a little trouble understanding your suggestion. Can you please clarify?

[yaooqinn]

Thank you @LuciferYang, I added a nit in the last commit and passed the test locally, so I didn't wait for the CI.

Merged to master