perfomance: increase performance by map usage

[pnsafonov]

Perfomance fix

[wader]

Thanks and thanks for profiling and looking into this 👍

One future improvement related to memory usage would be to use a *map[string]struct{} instead which i think would save some bytes (a pointer vs a pointer, length and capacity it think?) but the indirection would cost some performance. We can experiment with that later.

[wader]

Will probably do an additional PR soon if it makes sense to change it into a map[string]*Value so it can also be used by interp/decode.StructDecodeValue JQValueKey(name string) any

[pnsafonov]

Thanks and thanks for profiling and looking into this +1

One future improvement related to memory usage would be to use a *map[string]struct{} instead which i think would save some bytes (a pointer vs a pointer, length and capacity it think?) but the indirection would cost some performance. We can experiment with that later.

Change map[string]*Value to *map[string]*Value will not save any byte. map is implemented via pointer.

It can be checked by:

package main

import (
	"fmt"
	"unsafe"
)

// 8
type DataA struct {
	keys map[string]struct{} // ptr to map
}

// 8
type DataB struct {
	keys *map[string]struct{} // ptr to ptr
}

// 12
type DataC struct {
	id1 int32
	id2 int32
	id3 int32
}

// 24
type DataD struct {
	values []int // ptr to array, len, cap
}

// 8
type DataE struct {
	values *[]int // ptr to ptr (ptr to array, len, cap)
}

func main() {
	d1 := DataA{
		keys: make(map[string]struct{}),
	}
	m2 := make(map[string]struct{})
	d2 := DataB{
		keys: &m2,
	}
	d3 := DataC{}
	d4 := DataD{
		values: []int{1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
	}
	sl5 := []int{1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1}
	d5 := DataE{
		values: &sl5,
	}

	s1 := unsafe.Sizeof(d1)
	s2 := unsafe.Sizeof(d2)
	s3 := unsafe.Sizeof(d3)
	s4 := unsafe.Sizeof(d4)
	s5 := unsafe.Sizeof(d5)

	fmt.Printf("s1 = %d\n", s1)
	fmt.Printf("s2 = %d\n", s2)
	fmt.Printf("s3 = %d\n", s3)
	fmt.Printf("s4 = %d\n", s4)
	fmt.Printf("s5 = %d\n", s5)
}

It outputs (my machine is x64, pointer is 8 bytes):

s1 = 8
s2 = 8
s3 = 12
s4 = 24
s5 = 8

[wader]

Aha, yes i must have confused it with how a slice work