[C++] [Gandiva] Optimize Gandiva Cache

[likun666661]

Describe the enhancement requested

In Gandiva, it has been observed that the tool caches compiled expressions. However, when using the expression cache, Gandiva takes into account the schema, expr->ToString, and specific parameters. Nevertheless, in llvm_generator.cc, Gandiva still traverses the expressions to generate LLVM IR code and then produces specific JIT functions. Considering that llvm_generator traverses expressions and calculates the memory start positions of fields involved in the computation, we can further enhance Gandiva's caching mechanism.

Specifically, we can exclude the influence of the schema. Simultaneously, we can also exclude the field names' information involved in the expression computation. For example, for a schema {f0:int32, f1:int32} with an expression add(f0, f1), we can cache it initially. Then, for a schema {a0:int32, a1:int32, a2:int32} with an expression add(a1, a2), it should not require recompilation; it can directly reuse the JIT function generated by the expression {f0:int32, f1:int32}, add(f0, f1).

Component(s)

C++, C++ - Gandiva