Re: wrong query result with jit_above_cost= 0

Hi,

On 2018-07-07 21:41:05 +0200, Dmitry Dolgov wrote:
> Ok, looks like I found the issue. v_aggcontext & v_curaggcontext have nothing
> to do here (this change was just masking a problem by changing a memory context
> so that the wrong one will never be used). The problem was that in the
> llvmjit_expr in AGG_INIT_TRANS section we need to assign a current memory
> context from op->d.agg_init_trans.aggcontext (see the attached patch),
> otherwise we'll get in the situation when current memory context is hashcontext
> instead of aggcontext.

Nice catch! I pushed your fix, but I also made it set current_set.

> Also, I found one suspicious thing, in AGG_PLAIN_TRANS section we don't
> switch the memory context back in the branch with ExecAggTransReparent. I
> never found any consequences of that, but just in case I believe it makes sense
> to do so.

I'll look at that next.

> And the last thing - where can I find a documentation about how to properly
> apply patches for GDB & perf support to llvm? I remember they were posted here,
> and found some of them here [1] from Andres, but apparently part of them was
> already applied on top of llvm. Looks like for the gdb support I need to apply
> 0006-ORC-JIT-event-listener-support (since there is a gdb listener mentioned
> there), but with this patch I have an error:
>
> error: ‘ObjHandleT’ was not declared in this scope
>
> So I'm confused how should it be?

I've merged the GDB part into LLVM, and am about to merge the perf part
too. I plan to push a fix to PG adapting it to use the agreed upon /
merged LLVM APIs. Then you'll just need a recent LLVM
checkout. Unfortunately the relevant LLVM internal APIs have changed
quite rapidly over the last few releases (and a lot within individual
releases), so it's not easy to provide a patch for the individual versions.

Greetings,

Andres Freund