In-depth understanding of search engine spiders, their crawling strategies and keyword indexing mechanisms

One of the core functions of a search engine is to crawl and index Internet information through spider programs. The search engine spider will automatically browse the web and store the captured information in its index library, and then present the information through the keywords entered by the user.

How search engine spiders work

The task of search engine spiders is to discover and crawl web pages, and then perform data analysis and indexing. The crawling process can be roughly summarized into the following steps:

1. Discovered links: The spider first enters a new web page through a link on the page.
2. Page crawling: The spider downloads the web page pointed to by the link and stores its data in a temporary database.
3. Content analysis: Analyze the crawled web pages, eliminate invalid information, and finally compile useful data into the index database.

Crawling strategy analysis

Search engine spiders do not crawl web pages blindly, but crawl them effectively according to certain strategies, which mainly include the following strategies:

1. Depth-first strategy: After the spider finds a link, it goes deep into the link page until the crawl is completed, and then returns to the upper-level page to find the next link to crawl. Although this strategy ensures the comprehensiveness of links, it may cause low-weight pages to be crawled first.

2. Breadth first strategy: The spider will crawl all the links on the current page and then go to the next page to crawl. This strategy is often used on web pages with a flat structure to help increase the visibility of important pages.

3. Weight-first strategy: When implementing depth-first or breadth-first, spiders will determine the order of crawling based on the weight of the page or link. Typically, links with higher weight will be crawled first, while links with lower weight may rely on breadth first.

4. Revisit crawl: Spiders also periodically revisit crawled pages to retrieve the latest updated information. Revisit strategies are divided into all revisits and single revisits, depending on how often the web page is updated.

Keyword crawling and indexing

In the process of information capture, the identification and processing of keywords are crucial. Search engines need to preprocess web page content to form an effective index. The typical process is as follows:

1. Information crawling: The spider crawls the text information on the web page, removes useless HTML codes and format tags, and extracts pure text content.

2. Useless word filtering: The spider will filter out some common useless words that are meaningless to the search, such as “the”, “a”, etc., which can improve the accuracy of the index.

3. Dual index processing: After crawling the information, the page will be regarded as a combination of keywords, and then indexed a second time to form a mapping relationship between keywords and pages for quick response. User search needs.

Conclusion

Through the above analysis, it can be seen that search engine spiders follow scientific strategies when crawling web pages to ensure the acquisition and provision of effective information. The keyword crawling and indexing mechanism is also the guarantee for the efficient operation of search engines, ensuring that users can get the information they need in the shortest possible time.