SEARCH KEYWORD -- Query
Check mobile device using JavaScript
Sometimes developers want to know whether the user is using a mobile browser or a desktop browser so that they can build corresponding user experience. Although in many cases responsive web design would help solve component alignment issues, there are performance related considerations in some cases where some code should not be ran or some feature should not be available if user is on mobile browser. or vice versa This post will summarize a few ways which are commonly used to check whether a us...
CHECK,MOBILE BROWSER,MOBILE DEVICE,JAVASCRIPT 2021-10-02 01:36:16
A guide on installing and running Clickhouse on macOS
ClickHouse is a high-performance open-source columnar database management system developed by Yandex. Here are some of the key features of ClickHouse: Columnar storage: ClickHouse uses a columnar storage format, which allows it to efficiently store and retrieve data by column, rather than by row. This results in much faster query performance, especially for analytical and aggregate queries. Real-time data processing: ClickHouse is designed to handle real-time data processing and can handle bill...
CLICKHOUSE,MACOS 2023-02-15 06:04:55
An alternative way to parse URL in JavaScript
Normally when we need to process URL in JavaScript, we may use the location object. Then we can use location.hostname,location.href,location.port etc to get the information we need. In this post, we will parse an URL with an alternative way. We can use an URL to create a DOM object by calling document.createElement("a"). The complete code is: function parseURL(url) { var a = document.createElement('a'); a.href = url; return { source: url, protocol: a.protocol.replace(':',''), host: a.ho...
An easy way to log client side information to server
JavaScript debug is a very troublesome thing in web application development. Because many web browsers will not notify you if there is any error in the JavaScript codes you write. They just silently fail and block the following codes execution. In order to debug JavaScript codes, we need a good log mechanism which will help us log the error information,, we often need to log errors in JavaScript codes to server for debug purpose in a production web application, What should we do? The first ...
JavaScript log, Ajax,Image,Debug 2012-12-30 09:16:50
MySQL index optimization
Problem description: We need to access a very big table which has 40 million records. In the table, id is the primary key and program_id is indexed. When executing a select query: select * from program_access_log where program_id between 1 and 4000 The above query executes very slowly, we thought it was because there were too many records in the table. So we added id in the where condition to limit the search so that each time only half a million records would be read. select * fr...
MySQL,Index search, Partition 2012-12-26 13:14:20
How Google Utilizes Big Data for SERP
Google is an expert when it comes to big data. This is evident in their development of various techniques and open source tools which are used by the big data industry professionals. These tools and technique allow Google to sift through millions of different websites and enormous amounts of data in order to provide users with correct answers in a matter of milliseconds. But how does Google accomplish that with such precision? To answer that, we need to focus on the complex activities that go o...
A simple tutorial on GoLang connecting to Clickhouse
Go, also known as Golang, is a statically-typed, concurrent programming language created by Google. ClickHouse is a high-performance, column-oriented database management system that can be used for real-time data analysis. This tutorial will provide a deep dive into how to connect to ClickHouse from a Go program, including how to perform common database operations such as SELECT and INSERT statements. Before proceeding, it is assumed that you already have Go and ClickHouse installed on your mach...
GOLANG,CLICKHOUSE,TUTORIAL 2023-02-11 07:05:36
OpenLDAP Proxy -- rwm-map vs map
OpenLDAP proxy is used to proxy ldap request and response between clients and servers, different servers may have different representations/attributes to mean the same thing. For example, in one LDAP server, the firstName may be represented by firstName, it may be represented by givenName in a different server. However, from the client perspective, it only wants to get the firstName, it doesn't care about the backend attributes. In this case, attribute mapping can help provide a virtual view of ...
MAP,OPENLDAP,OPENLDAP PROXY,LDAP,RWM-MAP 2018-02-02 20:36:02
OpenLDAP Proxy -- slapd.conf
In the introductory post of OpenLDAP proxy, we mentioned that slapd.conf is the configuration file which tells the slapd service what to do. Apart from this, there is a dynamic way of configuring slapd where the configurations are stored in LDIF database. In the future, LDIF database will be the one for configuring slapd, the old style of slapd.conf is deprecated. The slapd.conf can be converted to LDIF style using the slapdtest command. slapdtest -f /etc/ldap/slapd.conf -F /etc...
OPENLDAP,OPENLDAP PROXY,SLAPD,SLAPD.CONF 2017-10-29 04:01:39
Inline IF and CASE statements in MySQL
There are times where running IF statements inside a query can be useful. MySQL provides a simple way to do this through the use of IF and CASE statements. The IF statement takes three arguments; the conditional, the true value and the false value. False and true values may be static values or column values. For example: SELECT IF(score > 100, 100, score) AS score FROM exam_results this will return the value in the score column limited to a maximum value of 100. IF statements can a...
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