Customized udf and udaf function statistics uv in SPARK SQL (using bitmap) When counting UVs in actual work, the count(distinct userId) method is generally used to count people, but this is not efficient. Suppose you are counting data in multiple dimensions. When one day you want to roll up the dimensions, then It is also […]
Tag: tmap
The use of javassist, and the simple implementation of the GenerateDaoProxy mechanism (getMapper method) in MyBatis using javassist
The use of javassist, and the simple implementation of the GenerateDaoProxy mechanism in MyBatis using javassist 1. What is javassist? 2. Simply use javassist: here we only consider simple implementation classes through interfaces 3. Provide tool classes for SqlSession 4. Dynamically generate a simple Dao implementation class: 1. What is javassist? Javaassist is a class […]
Redis Advanced (bitmap bloom filter)
Table of Contents 1. What is a Bloom filter? 2. Bloom filter characteristics 3. Usage scenarios of Bloom filter 4. Code practice, unity of knowledge and action 1. What is Bloom filter Bloom Filter is a probabilistic data structure with high space efficiency and fast processing speed, which is used to determine whether an element […]
[mmdetection] featmap_strides and finest_scale in ROIExtractor
Featmap_strides is wrong and results in no performance When I used FasterRCNN to run my own data set, I found that there was almost no performance (0.8%). Later I found the reason and found that it was: In FasterRCNN, the featmap_strides of the SingleROIExtractor in the second stage is written as [8, 16, 32, 64] […]
Redis: Using BitMap to implement user check-in
BitMap We can complete the check-in function through mysql. For example, the following table A user’s check-in is a record. If there are 10 million users and the average number of check-ins per person per year is 10, then the amount of data in this table per year will be 100 million. Each check-in requires […]
Redis’s BitMap implements distributed Bloom filter
Bloom Filter is an efficient probabilistic data structure used to determine whether an element belongs to a set. It stores and queries data by using hash functions and bit arrays, has fast insertion and query speeds, and takes up relatively little space. Introduce dependencies <!–Section–> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-aop</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-redis</artifactId> </dependency> <!– Database […]
Chapter 6 Android–ImageView, Bitmap
ImageView, and the TextView and EditText introduced earlier, all inherit from View and are all subclasses of View. ImageView is a view used to render images. View can be understood as a view or control. 1. Simple to use Place an image under the drawable-xxhdpi folder: Set this picture to ImageView in xml, so that […]
MyBatis custom mapping resultMap, processing one-to-many, many-to-one
1. Custom mapping resultMap Review: The query tag select must set the attribute resultType or resultMap, which is used to set the mapping relationship between the entity class and the database table resultType: automatic mapping, used when the attribute name is consistent with the field name in the table (or the underscore is set to […]
A geographical location information system based on OpenStreetMap shared geographical location data
Table of contents Preface 1 Chapter 1 Introduction 2 1.1 Research background and significance 2 1.2 Overview of GIS 2 1.3 The main work and entry point of this article 2 1.4 Organizational structure of this article 3 Chapter 2 Overview of geographical location information 4 2.1Geographical location data 4 2.2 OSM data structure 6 […]
Data structure – Bitmap for hashing applications, Bloom filter and hash cutting
Article directory Preface 1. Bitmap 1.1 The concept of bitmap 1. 2 Simulation and implementation of stl bitmap Bitmap applications 2. Bloom filter 2.1 Concept of Bloom filter Bloom filter search Bloom filter deletion problem Bloom filter advantages Bloom filter defects hash cut Foreword This blog mainly talks about some data structures that apply hashing_bitmaps […]