Quickly read very large tables as data frames

I have a very large table (30 million rows), and I want to load it as a data frame in R. read.table() has many convenient functions, but it seems that there are many logic in the implementation that will slow things down. As far as I'm concerned, I'm assuming that I know the type of column in advance, that the table doesn't contain any column ...

Posted by Johnlbuk on Fri, 17 Jan 2020 07:09:11 -0800

iOS uses FMDB and FMDB migration manager to upgrade the database version

FMDB is generally used for data saving in iOS. Generally, fields will not be modified or added after being defined. If it is strict, we need to add the function of adding fields to the database. At present, FMDB and FMDB migration manager are used in the project to save the database version number and upgrade the database Acco ...

Posted by freddykhalid on Thu, 02 Jan 2020 13:50:06 -0800

Android Chapter 3 SQLite database

1. Use execSQL API to operate the database. Step 1: create the Class MyOpenHelper implementation interface SQLiteOpenHelper, copy the constructor, onCreate and onUpgrade methods; Step 2, after creating the myOpenHelper object myOpenHelper, use the relevant API of myOpenHelper to operate the database. package com.xiaohui.create ...

Posted by janey on Thu, 26 Dec 2019 13:24:13 -0800

java implementation of online editing and flow of word documents

Using pageoffice to realize document online editing and document flow 1: process Draft documents in the modified traceless mode, open them in the forced trace mode when leaders annotate their opinions, open them in the approval mode when the clerk cleans up the draft, and open the released official documents in the final read-only mode. Amon ...

Posted by Ferenc on Wed, 25 Dec 2019 12:10:17 -0800

Autodesk Forge Viewer truly realizes single machine offline application

Autodesk Forge Viewer to truly implement stand-alone offline application) About the offline implementation of Autodesk Forge Viewer, the official has allowed exporting SVF and related documents, allowing users to deploy SVF and other documents to private servers, but this paper discusses another requirement. The customer requi ...

Posted by TechGuru on Mon, 23 Dec 2019 10:59:05 -0800

Fabric CA certificate management tutorial

Fabric CA is a certificate management tool of Hyperledger Fabric, which is very convenient for development and testing. In this tutorial, we will explore the use of fabric Ca and use it to complete user registration / Register and registration / Enrollment. Hyperledger Fabric is a licensed blockchain platform. Before accessing the Fabric networ ...

Posted by Scott_J on Sun, 15 Dec 2019 20:07:18 -0800

How to use multiple Guards in a Laravel application

The article was forwarded from the professional Laravel developer community with the original link: https://learnku.com/laravel/t... If you use Laravel For a while, you should have heard a lot about multiple identities.You should also have heard a lot about certification watchers.However, if you are unfamiliar with Laravel, multiple authentic ...

Posted by ThEoNeTrUeAcE on Mon, 18 Nov 2019 19:21:46 -0800

sqlite3 open, sqlite3 exec, slite3 close

sqlite3_open SQLite3 open function prototype: int sqlite3_open( const char *filename, /* Database filename (UTF-8) */ sqlite3 **ppDb /* OUT: SQLite db handle */ ); SQLite3 open is used to connect and open a database. If the database does not exist, a database file will be created and opened under the specified ...

Posted by webmazter on Sat, 26 Oct 2019 10:57:27 -0700

AsyncTask, SQLite, Contacts, AutoComplete TextView (Android)

Links to the original text: https://my.oschina.net/gal/blog/200185 This job is mainly to investigate the use of SQLite, get the information of mobile contacts (name, cell phone number, ...

Posted by Barb54 on Tue, 08 Oct 2019 19:01:31 -0700

Compatibility of Logic Operators of SQL Statements "AND", "&&"

Recently, I plan to transfer my blog to the typecho platform and choose a theme that I personally prefer. Akina for Typecho Theme Template Thank you for the open source sharing of the theme, but there was a "500 Database Query Error" problem at the beginning of the use process.Add the following code at the beginning of the index.php f ...

Posted by phpCCore Brad on Sun, 06 Oct 2019 09:15:08 -0700