Notice: Here we just learn to drive a car, not to build an engine. So I don’t dig deeper into how crawler work As we know Scrapy is a popular framework for crawling data. There is another library is called BeautifulSoup. What is Scrapy? An open source and collaborative framework for extracting the data you need from websites. What is Beautiful Soup? Beautiful Soup is a Python library for pulling data out of HTML and XML files.
Open my web blog again. Main purposes of this blog: Note technical knowledge. Note daily learning. Random writing.
What is Index? Indexes are used to find rows with specific column values quickly. Without an index, MySQL must begin with the first row and > then read through the entire table to find the relevant rows. What is B-Tree? It is a self-balancing search tree. When to use index? WHERE clause quickly. When having multiple indexes, MySQL uses the index that finds the smallest number of rows.