Kusto是否不支持正则表达式环顾？

Question

It seems that Kusto doesn't support regex lookarounds, as I get the following errors when I try to run the below commands. Am I using the wrong syntax? If this feature really isn't supported, where can I give feedback to vote for this feature?

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Positive Lookahead Test:

print(extract("t(?=t)", 0, "http"))

Expected Output: tt

Actual Error: Relop semantic error: 'extract()' has the following semantic error: SEM0420: Regex pattern is ill-formed: t(?=t).

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Negative Lookahead Test:

print(extract("t(?!t)", 0, "http"))

Expected Output: tp

Actual Error: Relop semantic error: 'extract()' has the following semantic error: SEM0420: Regex pattern is ill-formed: t(?!t).

Answer 1

Kusto uses the re2 library: https://github.com/google/re2/wiki/Syntax , as mentioned here: https://docs.microsoft.com/en-us/azure/kusto/query/re2

What you're trying to achieve isn't supported by that library - see https://github.com/google/re2/wiki/WhyRE2 :

As a matter of principle, RE2 does not support constructs for which only backtracking solutions are known to exist. Thus, backreferences and look-around assertions are not supported.

As for your other question, feature requests can be submitted/upvoted @ https://aka.ms/adx.uservoice