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azure-cognitive-search

Azure Search - Search Score

I am currently using Azure Search to perform product searches on my website.

I have the following indexes:

A: Index with 55,000 documents
B: Inde with 16 documents

All documents in index B were filled with index A documents

When performing a simple search in the 2 indices with the same parameters the results are not what I expect.

Example:

Index A:

Query String: search=kfc

Result sorted by search.score descending:

ProductoName - search.score
KFC Product1 - 1.6514521
KFC Product2 - 1.5482594

Index B:

Query String: search=kfc

Result sorted by search.score descending:

ProductoName - search.score
KFC Product2 - 0.21555252
KFC Product1 - 0.13616839

I am surprised the order of the results by search score changes, because they are exactly the same data only the amount of documents changes

The amount of documents affect in the assignment of search score ?, Could you indicate where I can read about it, I look in the documentation but I did not find anything about it

Could you explain to me why the order of the products is affected if it is the same information? :(

The Index has no Scoring Profile and is exactly the same information

Solution

  • Your analysis is correct, scoring (and thus ranking) is indeed affected by the number of documents in the index. To compute scores we use some statistical characteristics of the data corpus, such as the frequency of each term across the entire corpus and within each document.

    The article How full text search works in Azure Search explains this in great detail. In particular, the section on Scoring goes into how frequencies (term frequency, document frequency) are used.