Index Ranking Phases

The Coveo Cloud Platform ranking engine is the component responsible for the ordering of query results. Basically, it makes sure the most relevant results are shown before less relevant ones based on your settings.

This mechanism behind the ranking process can be compared to a funnel. Starting with all items, the index receives a query from a user, isolates items in which the user identity can be found in the permission groups (see Group and Granted Security Identities, Permission Sets, and Permission Levels), and then only keeps the items that match the query.

The ranking process is separated into five phases, each of them working on the items sorted by the preceding phase.

The Coveo Cloud Platform natively uses 16 pre-tuned ranking weight factors during these phases. Among the most important ones, the criteria with the biggest relevance impact are term proximity, item modified date (most recent), and term frequency. Each of these 16 criteria has been optimized over years of experience with a wide variety of indexed content to determine highly satisfying out-of-the-box relevance scores of items in most cases. You can still carefully tune these parameters when needed (see Managing Query Pipeline Ranking Weights). You can also troubleshoot ranking when a factor score seems too high or too low (see Using the JavaScript Search Debug Panel).

While you can use several parameters to tune the index ranking engine, you must make changes carefully to prevent negative performance or ranking collateral effects. It is recommended to contact Coveo Support to get recommendations to address your index ranking issues.

Phase

Ranking factor
(Label in Debug panel)

Applies to n best ranked items from the previous phase
1 Term in title (Title)1 All matching security and query
Term in concepts (Concept)1
Term in summary (Summary)1
Terms in address (URI)2
Term has formatting (Formatted)2
Term casing (Casing)2
Term correlation within stemming classes (Relation)2
2 Item modified recently (Date)1 50 000
Item quality evaluation (Quality)2
Item in user language (QRE)2
Item title match (Title)2
Source rating (Source)2
Custom ranking weight (Custom)2
3 Collaborative rating weight (Collaborative Rating)3 1002
4 Term frequency (Frequency)1 1002
Term correlation (Correlation)2
Term Frequency–Inverse Item Frequency (TF-IDF)2
5 Term proximity (Adjacency)1 100

Note 1: Configurable in ranking weight rules (see Managing Query Pipeline Ranking Weights).

Note 2: Default value that is configurable with the assistance of Coveo Support.

Note 3: Not exploited in Coveo Cloud V2.

The relative importance of each of the ranking criteria is difficult to establish, since each criteria score depends on many factors, such as the number of terms in the query, the type of sources that are indexed, the individual terms in the query and the number of items in the index.