colexec: add support for JSONFetchText binary operator

[yuzefovich]

Add support for JSONFetchText binary operator. For more details, see #49463.

Blocked by #49780.

[deathname]

Hi, Can I work on this issue

[yuzefovich]

That would be great! I'll assign the issue to you.

[deathname]

Thanks, @yuzefovich

I think this issue is similar to https://github.com/cockroachdb/cockroach/pull/49818/files.
I just need to add one more switch case handling for JSONFetchText and return type.DString in overloads_bin.go just as similar to the above-mentioned url or there is something else ?

[yuzefovich]

Yes, I think the solution will be very similar to #49818.

[deathname]

What should be expected output for EXPLAIN (VEC) SELECT _json -> 2 ->> 'a' FROM many_types as per vectorize_overloads input
--- Node 1 -> *rowexec.tableReader is it correct ?

[yuzefovich]

No, this means that the old row-by-row engine is used, not the vectorized engine.

I think you might be missing a few things. Please take a look at the detailed message here.

[yuzefovich]

I think it is currently pretty hard to implement due to some infrastructure limitations between the interactions of datum-backed arguments and non-datum-backed result, so I'm removing "good first issue" label and making the issue unassigned. Apologies for mis-triaging the issue initially.

[haseth]

Hi @yuzefovich, this should be pretty simple to pick and is not blocked by #49780 I think. Can you check it once?
JSONFetchText only requires types.String as 2nd operand.

[yuzefovich]

@haseth I think you're misunderstanding the limitation described by #49780. Currently we are not able to support a case of binFn(datumVec, datumVec or <native type>) = <native type>, and this is exactly the case we have here - binFn(datumVec, coldata.Bytes) = coldata.Bytes. To be more precise, we don't support a case when at least one argument is represented via datumVec but the result is not represented via datumVec but a "native vector" instead.