Potentially a dumb question about which

Potentially a dumb question about which type of "query" is the most performant in Convex

5 Replies

Read the docs explaining the performance gain of using indexes (I loved the explanation). I have usecases where I want to grab a document by it's _id . And I was wondering if

   const space = await db.query("spaces").filter((q) => {
        return q.eq("_id", spaceId)
    }).unique();

   const space = await db.query("spaces").filter((q) => {
        return q.eq("_id", spaceId)
    }).unique();

is faster or

 const space = await db.get(spaceId) as Document<"spaces">  ;

 const space = await db.get(spaceId) as Document<"spaces">  ;

    const space = await db
        .query("spaces")
        .withIndex("by_id", (q) =>
            q.eq("_id", spaceId)
        ).unique()

    const space = await db
        .query("spaces")
        .withIndex("by_id", (q) =>
            q.eq("_id", spaceId)
        ).unique()

And if it's the last option, is it possible to index by _id ?

sujayakar•3y ago

hi @DavidKim ! not a dumb question at all. (2) and (3) are pretty much the same, where it's a single lookup against the index. (1) is a full table scan, where it has to look at every document in spaces (I think you already read it, but https://docs.convex.dev/understanding/indexes-and-query-perf has more details). so, I'd recommend using (2), since it's less verbose. we currently don't allow including _id as an indexed field in user defined indexes, but let us know if that'd be helpful!

Introduction to Indexes and Query Performance | Convex Developer Hub

How do I ensure my Convex database queries are fast

DavidKimOP•3y ago

If 2 is the same as indexing by _id, I have no need for indexing by _id ! so 2 it is ! thank you ! From DX perspective, I think the only downside of

    const space = await db.get(id) as Document<"spaces">;

    const space = await db.get(id) as Document<"spaces">;

is that I have to type it with as where as the indexed query can infer the type for me but not sure if this is a big deal

sshader•3y ago

For the types, I believe that if id has type Id<"spaces" the return type of await db.get(id) will be Document<"spaces"> | null so alternatively const space: Document<"spaces"> = (await db.get(id))! should work (or explicitly handling the null). (and actually our latest release has unique returning a Document or null too, so you'd need the null handling with (3) as well)

DavidKimOP•3y ago

ahh you're right; it wasn't inferring properly because I originally did not type the id correctly. Thank you !!

Potentially a dumb question about which

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