英文:
How to concurrently iterate through an sql result set in Golang?
问题
next()方法是顺序执行的，有没有一种方法可以并发地迭代循环？
我有一个包含20万行的结果集，我正在顺序地遍历每一行，并对每一行进行逻辑操作，我想将其拆分。
英文:
The next() method is sequential, is there a way to concurrently iterate through the loop?
I have a result set of 200k rows that I am looping through sequentially and doing logic on each row and want to split it up.
答案1
得分: 9
你从查询中获得的sql.Rows不能同时使用（我相信）。
但你可以在goroutine中完成大部分繁重的工作。
这是一个示例（不可工作，但接近），在Play上：
package main
import "fmt"
import "sql"
type Row struct {
x string
y string
z string
}
func processor(ch chan Row) {
for row := range <-ch {
// 做一些很棒的事情
}
}
func main() {
ch := make(chan Row)
// 两个处理器goroutine
go processor(ch)
go processor(ch)
rows := db.Query("select x,y,z from whatever")
for rows.Next() {
var row Row
if err := rows.Scan(&row.x, &row.y, &row.z); err != nil {
// 处理错误
} else {
ch <- row
}
}
}
英文:
The sql.Rows you get back from your query can't be used concurrently (I believe).
but you can do most of the heavy lifting in goroutines.
Here is an example (non-working, but close), on Play
package main
import "fmt"
import "sql"
type Row struct {
x string
y string
z string
}
func processor(ch chan Row) {
for row := range <-ch {
// be awesome
}
}
func main() {
ch := make(chan Row)
// two handler go routines (current processors)
go processor(ch)
go processor(ch)
rows := db.Query("select x,y,z from whatever")
for rows.Next() {
var row Row
if err := rows.Scan(&row.x, &row.y, &row.z); err != nil {
// do something with error
} else {
ch <- row
}
}
}
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