Hello Andres, Attached is a patch on top of v2-0026-WIP-expression-eval-relative-pointer-suppport.patch that eliminates the const pointer references to fmgrInfo in the generated code.
FmgrInfos are now allocated like the FunctionCallInfos are (ExprBuilderAllocFunctionMgrInfo()) and are initialized with expr_init_fmgri(). Unfortunately, inside expr_init_fmgri(), I had to emit const pointers to set fn_addr, fn_extra, fn_mcxt and fn_expr. fn_addr, fn_mcxt should always be the same const pointer value in between two identical calls. So this isn't too bad? fn_extra is NULL most of the time. So not too bad? fn_expr is very difficult to eliminate because it is allocated way earlier. Is it something that will have a const pointer value in between two identical calls? (don't know enough about plan caching..I ran the same query twice and it seemed to have different pointer values). Eliminating this pointer poses a similar challenge to that of FunctionCallInfo->context. fn_expr is allocated quite early on. I had tried writing ExprBuilderAllocNode() to handle the context field. The trouble with writing something like expr_init_node() or something even more specific like expr_init_percall() (for the percall context for aggs) as these structs have lots of pointer references to further pointers and so on -> so eventually we would have to emit some const pointers. One naive way to handle this problem may be to emit a call to the _copy*() functions inside expr_init_node(). It wouldn't be as performant though. We could decide to live with the const pointers even if our cache key would be the generated code. The caching layer could be made smart enough to ignore such pointer references OR we could feed the caching layer with generated code that has been passed through a custom pass that normalizes all const pointer values to some predetermined / sentinel value. To help the custom pass we could emit some metadata when we generate a const pointer (that we know won't have the same const pointer value) to tell the pass to ignore it. Soumyadeep
v1-0001-jit-Eliminate-const-pointer-to-fmgrinfo.patch
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