DSL: match(): support patterns array so Director renderer can make use of it

[Al2Klimov]

Is your feature request related to a problem? Please describe.

Big OR trees of match() on the same subject are expensive, but Tom considers one big rendered regex less readable.

Describe the solution you'd like

• We support match(["a*", "b*", "c*"], x)
• At best we cache const and never-modified DSL expression results if we can
• Director renders that one match call

Describe alternatives you've considered

• Assign where filter rendered as match("a*",x)||match("b*",x)||match("c*",x)||... icingaweb2-module-director#2661
• DSL magically optimises big OR trees of match() on the same subject (IMAO cheaty)

Additional context

https://github.com/orgs/Icinga/projects/29

[julianbrost]

Big OR trees of match() on the same subject are expensive

I mean this is the problem, so we should put more effort into finding and fixing the cause. The suggestion in this issue feels more like working around the symptoms to me.

[Al2Klimov]

No and no. "the cause" is simply that the DSL is not smart. Or that Director rendering is not smart (for readability reasons). I could make the DSL smarter, see my 2nd considered alternative, but this would require:

• operator== for every single class inheriting Expression in the AST
• magic handling of match() in OR trees

It's cheaty, magic and someone has to spend time on the two bullets above.