pre-alloc search post body for index_search

[trim21]

Pull Request

map initialization without length map cause many allocs, adding a fixed known length to avoid.

this is a minor change I guess I don't need to create a issue for it?

What does this PR do?

Fixes #<issue_number>

PR checklist

Please check if your PR fulfills the following requirements:

• Does this PR fix an existing issue?
• Have you read the contributing guidelines?
• Have you made sure that the title is accurate and descriptive of the changes?

Thank you so much for contributing to Meilisearch!

[alallema]

Hi @trim21,
Thank you so much for contributing to Meilisearch ❤️
I'm very sorry I didn't take care of your PR instead. I'm not sure to understand well your modification, I'm not so comfortable with make(). Also, unfortunately I won't be here next week but I'll take care of your PR when I get back on the 5th.
Thanks again

[trim21]

map initlized without hint, may cause go to to alloc may times when setting items.

currently map[K]V{} is just same with make(make[K]V) (or make(make[K]V, 0))

package main

import (
	"runtime"
	"testing"
)

func BenchmarkMapMake(b *testing.B) {
	for i := 0; i < b.N; i++ {
+		m := make(map[int]int, 14)
		for j := 0; j < 14; j++ {
			m[j] = j
		}
		runtime.KeepAlive(m)
	}
}

func BenchmarkMap(b *testing.B) {
	for i := 0; i < b.N; i++ {
+		var m = map[int]int{}
		for j := 0; j < 14; j++ {
			m[j] = j
		}
	}
}

cpu: AMD Ryzen 7 5800X 8-Core Processor
BenchmarkMapMake-16      4550072               268.6 ns/op           577 B/op          1 allocs/op
BenchmarkMap-16          1926235               627.5 ns/op           918 B/op          3 allocs/op
PASS

[alallema]

Thanks for this PR @ and for contributing to Meilisearch ❤️
LGTM! And thanks you for the explanation

[alallema]

bors merge

[bors]

Build succeeded:

• integration-tests (go current version)
• integration-tests (go latest version)
• linter