docsearch/docs/src/inside-the-engine.md

layout	title
two-columns	Inside the engine

This page will explain in more detail how the crawler extracts content from your page every 24h, and how it ranks the results.

Crawling

Each crawl will begin its journey by the value of the start_urls you have in your config. It will read those pages and recursively extract and follow every link in those pages until it has browsed every compliant page.

If you have explicitly defined a sitemap.xml, our crawler will scrap every provided and compliant page. We do recommend using a sitemap since it clearly exposes URLs to crawl and avoid missing pages that aren't linked from another one.

Extracting content

Building records using the scraper is pretty intuitive. According to your settings, we extract the payload of your web page and index it, preserving your data's structure. This is achieved in a simple way:

• We read top down your web page following your HTML flow and pick out your matching elements according to their levels based on the selectors_level defined.
• We create a record for each paragraph along with its hierarchical path. This construction is based on their time of appearance along the flow.
• We index these records with the appropriate global settings (e.g. metadata, tags, etc.)

Note: The above process performs sanity tests as it scrapes to detect errors. If indeed there are any serious warnings, it will abort and hence not overwrite your current index. These checks ensure that your dedicated index isn't flushed.

Ranking records

Algolia always returns the most relevant results first, using a tie-breaking approach. DocSearch will first search for exact matches in your keywords then fallback to partial matches. Those results will then be ordered based, once again, on the page hierarchy, as extracted from the selectors.

The default strategy is to promote records having matching words in the highest level first. Thus if two results have the same matching words, the one having them in the highest level (lvl0) will be ranked higher. We also use the position of the matching words. The sooner they appear within the HTML flow, the higher the record will be ranked.

The relevancy is based on several factors and can be customized according to the Algolia tie-breaking method.

You can boost pages depending on their URLs. This is done from the start_urls and its page_rank attributes. It is a numeric value (defaults to 0). The higher it is, the higher results from the matching pages will be ranked. For example all pages with a page_rank of 5 will be returned before pages with a page_rank of 1.

You could even change the relevancy strategy by overwriting the default customRanking used by the index by using the custom_settings option of your config.