| package main | |
| import ( | |
| "bytes" | |
| "fmt" | |
| "io/ioutil" | |
| "log" | |
| "mime/multipart" | |
| "net/http" | |
| "os" |
| def Check(a, b): | |
| dist = ((a[0] - b[0]) ** 2 + 550 / ((a[1] + b[1]) / 2) * (a[1] - b[1]) ** 2) ** 0.5 | |
| calibration = (a[1] + b[1]) / 2 | |
| if 0 < dist < 0.25 * calibration: | |
| return True | |
| else: | |
| return False |
| // Copyright (c) 2017 Ismael Celis | |
| // Permission is hereby granted, free of charge, to any person obtaining a copy | |
| // of this software and associated documentation files (the "Software"), to deal | |
| // in the Software without restriction, including without limitation the rights | |
| // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | |
| // copies of the Software, and to permit persons to whom the Software is | |
| // furnished to do so, subject to the following conditions: | |
| // The above copyright notice and this permission notice shall be included in all |
| Using this property of ObjectId and also taking into consideration the fact that _id is always indexed, we can devise following approach for pagination: | |
| Fetch a page of documents from database | |
| Get the document id of the last document of the page | |
| Retrieve documents greater than that id | |
| In Mongo Shell your pagination code looks something like this | |
| // Page 1 | |
| db.students.find().limit(10) |
| Lưu ý khi return không nên return biến pointer bởi lẽ hệ thống phải tạo lại biến pointer mới rồi copy dữ liệu mà biến con trỏ cần return trỏ tới chứ không lấy luôn được con trỏ return này đâu do nó sẽ bị hủy sau khi return xong. |
| package main | |
| import ( | |
| "fmt" | |
| "time" | |
| ) | |
| const MaxGoroutines = 5 | |
| type WorkerPool struct { |
| package parallel | |
| import ( | |
| "sync" | |
| ) | |
| // Func is the function to run concurrently. | |
| type Func func() error | |
| // Run calls the passed functions in a goroutine, returns a chan of errors. |
| func merge(cs ...<-chan int) <-chan int { | |
| out := make(chan int) | |
| var wg sync.WaitGroup | |
| wg.Add(len(cs)) | |
| for _, c := range cs { | |
| go func(c <-chan int) { | |
| for v := range c { | |
| out <- v | |
| } | |
| wg.Done() |
| { "_id": 1, "color": "red", "date": ISODate("2013-05-10T00:00:00Z") } | |
| { "_id": 2, "color": "blue", "date": ISODate("2016-10-20T00:00:00Z") } | |
| { "_id": 3, "color": "green", "date": ISODate("2015-09-14T00:00:00Z") } | |
| { "_id": 4, "color": "green", "date": ISODate("2015-07-19T00:00:00Z") } | |
| { "_id": 5, "color": "red", "date": ISODate("2017-01-04T00:00:00Z") } | |
| { "_id": 6, "color": "blue", "date": ISODate("2014-03-06T00:00:00Z") } | |
| result = db.books.aggregate([ | |
| { $sort: { "date": -1 } }, | |
| { $group: { |
A running example of the code from:
This gist creates a working example from blog post, and a alternate example using simple worker pool.
TLDR: if you want simple and controlled concurrency use a worker pool.