#33145 cache namespace string key in FlinkStateInternals

[je-ik]

Fixes #33145

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[je-ik]

R: @Abacn @kennknowles

Would you have time to review please? The test failures seem unrelated to this PR.

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[Abacn]

Thanks, just one question - now .stringKey is resolved earlier (in constructor) instead of in method calls. Is stringKey guaranteed to be available at that stage?

[je-ik]

Thanks, just one question - now .stringKey is resolved earlier (in constructor) instead of in method calls. Is stringKey guaranteed to be available at that stage?

This is why I made WindowNamespace immutable. Therefore yes, it should be available and constant for the whole lifecycle of the namespace.

[Abacn]

thank you!