loiclec commented 1 year ago

Pull Request

Related issue

Fixes (when merged into meilisearch) https://github.com/meilisearch/meilisearch/issues/3125

What does this PR do?

We now map multi-word synonyms to phrases instead of loose words. Such that the request:

btw I am going to nyc soon

is interpreted as (when the synonym interpretation is chosen for both btw and nyc):

"by the way" I am going to "New York City" soon

instead of:

by the way I am going to New York City soon

This prevents queries containing multi-word synonyms to exceed to word length limit and degrade the search performance.

In terms of relevancy, there is a debate to have. I personally think this could be considered an improvement, since it would be strange for a user to search for:

good DIY project

and have a result such as:

{
    "text": "whether it is a good project to do, you'll have to decide for yourself"
}

However, for synonyms such as NYC -> New York City, then we will stop matching documents where New York is separated from City. This is however solvable by adding an additional mapping: NYC -> New York.

Performance

With the old behaviour, some long search requests making heavy uses of synonyms could take minutes to be executed. This is no longer the case, these search requests now take an average amount of time to be resolved.

curquiza commented 1 year ago

Checked with @gmourier, since this PR has a product impact and we don't get any approval from the product team yet on this, don't merge it until @gmourier validates it 😇