[Rust] Memory is never released

[asfimport]

Another embarrassing bug ... the code was calling the wrong method to release memory and wasn't releasing memory.

I have added some benchmarks for testing performance of creating arrays (and dropping them) and these are working well now after fixing the memory bug.

Reporter: Andy Grove / @andygrove
Assignee: Andy Grove / @andygrove

PRs and other links:

• GitHub Pull Request #1860

_{Note: This issue was originally created as ARROW-2420. Please see the migration documentation for further details.}

[asfimport]

Andy Grove / @andygrove:
PR: #1860

[asfimport]

Antoine Pitrou / @pitrou:
Issue resolved by pull request 1860
#1860