Meilisearch

wakuwaku treats Meilisearch as one more data source behind the same Db<S, C> handle you use for PostgreSQL and Redis. Three things set a search engine apart from a database, and the Meilisearch module is shaped around them:

• Queries may come straight from end users, even from a browser that talks to Meilisearch directly. Filters and sorts are therefore typed and safe to deserialize from client JSON.
• An index is never the source of truth. It holds a projection of data that lives elsewhere (usually a SQL table), so the important writes are the ones to that source, not to the index.
• An index has to be kept in sync with that source, and the ways this can go wrong are well known. The sync helpers handle the parts that are the same in every project.

Enabling the featureCopy Anchor Link

Meilisearch support is behind the meilisearch feature of wakuwaku. Your documents and filter fields are (de)serialized with serde, so add serde with its derive macros, and serde_json if you parse client requests yourself:

[dependencies]
wakuwaku = { version = "1.0.0-rc3", features = ["meilisearch"] }
serde = { version = "1", features = ["derive"] }
serde_json = "1"

The feature enables wakuwaku::entity::meilisearch (the wakuwaku-entity crate, re-exported as wakuwaku::entity) and re-exports the SDK it is built on (meilisearch-sdk 0.33) as wakuwaku::deps::meilisearch_sdk. Use that path for Client, Settings and the error type, so the versions always match.

Describing an indexCopy Anchor Link

An index is described once, by a marker type implementing SearchIndex. That type is also an Entity, so everything you know about capabilities applies to it. A description has three parts: the document, the fields, and the index itself.

The documentCopy Anchor Link

The document is what a search may return. Keep it a separate type from the row it is built from, and put only data every searcher may see in it: a frontend holding a tenant token can read every displayed attribute of every document its scope allows.

use serde::{Deserialize, Serialize};

/// What a search may return. Only data every searcher may see goes here.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct PostDocument {
    pub id: i64,
    pub workspace_id: i64,
    pub author_id: i64,
    pub title: String,
    pub summary: String,
    pub tags: Vec<String>,
    pub published_at: i64,
}

The filterable and sortable fieldsCopy Anchor Link

Each index lists the attributes searches may filter on, and those they may sort on, as fieldless enums implementing Field. ALL lists every variant; name gives the attribute name in the documents (use dots for nested attributes, such as author.id). Derive Deserialize so clients can name the fields in JSON.

use wakuwaku::entity::meilisearch::filter::Field;

/// Attributes searches may filter and facet on.
#[derive(Debug, Clone, Copy, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum PostFilter {
    WorkspaceId,
    AuthorId,
    Tags,
    PublishedAt,
}

impl Field for PostFilter {
    const ALL: &'static [Self] = &[
        Self::WorkspaceId,
        Self::AuthorId,
        Self::Tags,
        Self::PublishedAt,
    ];

    fn name(self) -> &'static str {
        match self {
            Self::WorkspaceId => "workspace_id",
            Self::AuthorId => "author_id",
            Self::Tags => "tags",
            Self::PublishedAt => "published_at",
        }
    }
}

/// Attributes searches may sort on.
#[derive(Debug, Clone, Copy, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum PostSort {
    PublishedAt,
}

impl Field for PostSort {
    const ALL: &'static [Self] = &[Self::PublishedAt];

    fn name(self) -> &'static str {
        match self {
            Self::PublishedAt => "published_at",
        }
    }
}

These enums are the single source of truth for what is filterable. When the settings are applied, the index gets exactly these filterable and sortable attributes, and a filter or sort naming anything else can't be built in Rust or deserialized from JSON. An index with nothing to filter or sort on uses NoField.

The index itselfCopy Anchor Link

use wakuwaku::deps::meilisearch_sdk::settings::{PaginationSetting, Settings};
use wakuwaku::entity::Entity;
use wakuwaku::entity::meilisearch::SearchIndex;

/// The `posts` index: a projection of the `post` table.
pub struct PostIndex;
impl Entity for PostIndex {}

impl SearchIndex for PostIndex {
    const UID: &'static str = "posts";
    const PRIMARY_KEY: &'static str = "id";
    type Key = i64;
    type Document = PostDocument;
    type Filterable = PostFilter;
    type Sortable = PostSort;

    fn settings() -> Settings {
        Settings::new()
            .with_searchable_attributes(["title", "summary", "tags"])
            .with_displayed_attributes([
                "id",
                "workspace_id",
                "author_id",
                "title",
                "summary",
                "tags",
                "published_at",
            ])
            .with_pagination(PaginationSetting { max_total_hits: 1000 })
    }
}

settings() is only written to Meilisearch when you run ApplySettings, typically once per deployment.

Indexes, entities and capabilitiesCopy Anchor Link

Because each index is its own entity, a query that searches PostIndex has the effect Read<PostIndex>, and a write to it has the effect Write<PostIndex>. Note what this does not say: searching the projection is not Read<Post>, and writing the index does not grant write access to the post table. A search service can read the index without any access to the database, and an indexer service can write the index without being able to write anything else.

Map capabilities to Meilisearch API keys when you wire handles:

The type system proves routing: code wired to a Db<MeiliSource, ReadOnly> never issues a write. The API key is what makes Meilisearch itself refuse. Use both, as you would keep a replica read-only in PostgreSQL.

use wakuwaku::deps::meilisearch_sdk::client::Client;
use wakuwaku::deps::meilisearch_sdk::errors::Error;
use wakuwaku::entity::meilisearch::MeiliSource;
use wakuwaku::entity::{Db, ReadOnly};

/// A handle that may search every index and write none.
pub fn search_handle(url: &str, search_key: &str) -> Result<Db<MeiliSource, ReadOnly>, Error> {
    let client = Client::new(url, Some(search_key))?;
    Ok(Db::new(MeiliSource::new(client)))
}

MeiliSource wraps the client in an Arc, so cloning a handle is cheap.

Index settings are security settingsCopy Anchor Link

Once a frontend talks to Meilisearch, or clients choose facets and sorts through your server, the index settings decide what they can learn. Review them like access rules:

• displayedAttributes defaults to every attribute. Keep secrets out of the document type, and list the displayed attributes anyway.
• Every filterable attribute is also a facet. A facet reveals value counts among the documents the client may see.
• pagination.maxTotalHits bounds how deep a client can page.
• Any embedder configured on the index can be triggered by any client allowed to search it.

Next stepsCopy Anchor Link