Github user viirya commented on the issue:
https://github.com/apache/spark/pull/18687
> So far, we do not support dynamic SQL statement, but this is a potential
feature we can explore in the future. A global statement cache and management
can reduce the optimization costs, especially when our CBO optimizer is more
advanced.
I agree. The dynamic statement cache is used to reduce the costly
preparation process by reusing prepared (parsed, analyzed and optimized)
statement. IIUC, this only works for identical dynamic SQL statements. When CBO
optimizer goes more advanced and more costly, the statement cache might help
reduce the cost for identical statements.
The current cache in SparkSQL is not for statement cache, but for query
plan fragment (and its execution result) cache. A query doesn't need to be
identical to cached query plan. It can reuse the cached plan even when the
cached one is just a fragment of it.
So seems to me they are orthogonal and can be complementary.
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