expression: implement vectorized evaluation for builtinJSONMergeSig

[js00070]

What problem does this PR solve?

Implement vectorized evaluation for builtinJSONMergeSig mentioned in #12104

What is changed and how it works?

about 40% faster

BenchmarkVectorizedBuiltinJSONFunc/builtinJSONMergeSig-VecBuiltinFunc-4                      482           2282113 ns/op          949025 B/op      14082 allocs/op
BenchmarkVectorizedBuiltinJSONFunc/builtinJSONMergeSig-NonVecBuiltinFunc-4                   386           3197396 ns/op         1019904 B/op      14752 allocs/op

Check List

Tests

• Unit test

[zyxbest]

/run-unit-test

[codecov]

Codecov Report

Merging #12916 into master will not change coverage.
The diff coverage is n/a.

@@             Coverage Diff             @@
##             master     #12916   +/-   ##
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  Coverage   80.1577%   80.1577%           
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  Files           468        468           
  Lines        110018     110018           
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  Hits          88188      88188           
  Misses        15097      15097           
  Partials       6733       6733

[js00070]

@XuHuaiyu
I did several times of benchstat, the results are unstable because of my CPU condition(the frequency is changing on different temperature), but we can see my original code is faster than the approch like you mentioned.

name                                                                old time/op    new time/op    delta
VectorizedBuiltinJSONFunc/builtinJSONMergeSig-VecBuiltinFunc-12        822µs ± 1%    1064µs ± 0%  +29.47%  (p=0.000 n=19+17)
VectorizedBuiltinJSONFunc/builtinJSONMergeSig-NonVecBuiltinFunc-12    1.08ms ± 1%    1.30ms ± 1%  +20.19%  (p=0.000 n=19+20)

name                                                                old time/op    new time/op    delta
VectorizedBuiltinJSONFunc/builtinJSONMergeSig-VecBuiltinFunc-12        906µs ± 1%    1064µs ± 0%  +17.38%  (p=0.000 n=19+17)
VectorizedBuiltinJSONFunc/builtinJSONMergeSig-NonVecBuiltinFunc-12    1.18ms ± 1%    1.30ms ± 1%   +9.60%  (p=0.000 n=19+20)

name                                                                old time/op    new time/op    delta
VectorizedBuiltinJSONFunc/builtinJSONMergeSig-VecBuiltinFunc-12       1.02ms ± 1%    1.06ms ± 0%   +4.59%  (p=0.000 n=19+17)
VectorizedBuiltinJSONFunc/builtinJSONMergeSig-NonVecBuiltinFunc-12    1.32ms ± 1%    1.30ms ± 1%   -1.87%  (p=0.000 n=19+20)

the code which produces new.txt is as follow

	result.ReserveJSON(nr)
	for i := 0; i < nr; i++ {
		nullFlag := false
		jsonVal := make([]json.BinaryJSON, 0, len(b.args))
		for j := 0; j < len(b.args); j++ {
			if argBuffers[j].IsNull(i) {
				result.AppendNull()
				nullFlag = true
				break
			}
			jsonVal = append(jsonVal, argBuffers[j].GetJSON(i))
		}
		if !nullFlag {
			result.AppendJSON(json.MergeBinary(jsonVal))
		}
	}

[XuHuaiyu]

LGTM

[qw4990]

LGTM, WELL DONE.

[sre-bot]

Your auto merge job has been accepted, waiting for 13003

[sre-bot]

/run-all-tests

[sre-bot]

/run-all-tests