MONGOID-5918 Support BSON::Vector field type - #6162
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comandeo-mongo merged 1 commit intoJul 2, 2026
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Declaring a field with type: BSON::Vector now stores the value as a BSON binary of the vector subtype and reads it back as a BSON::Vector, preserving dtype and padding. The extension is guarded so Mongoid still loads on bson-ruby < 5.1, which predates BSON::Vector. Querying by an exact vector value is not supported because BSON::Vector subclasses Array; use $vectorSearch for similarity queries.
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Pull request overview
Adds first-class Mongoid field support for BSON::Vector, ensuring vector fields persist as BSON binary vector subtype (9) and are demongoized back to BSON::Vector with dtype/padding preserved (instead of being treated as a plain Array).
Changes:
- Introduces a
Mongoid::Extensions::Vectorextension that mongoizes vectors toBSON::Binary.from_vectorand demongoizes vector binaries back toBSON::Vector. - Wires the new extension into Mongoid’s extension load path.
- Adds RSpec coverage for mongoize/demongoize behavior and persistence round-trips (gated to bson-ruby
>= 5.1).
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
| lib/mongoid/extensions/vector.rb | Adds mongoize/demongoize behavior for BSON::Vector to persist as vector-subtype BSON binary. |
| lib/mongoid/extensions.rb | Requires the new vector extension so it is loaded with other core extensions. |
| spec/mongoid/extensions/vector_spec.rb | Adds unit + integration specs for correct vector persistence and demongoization behavior. |
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| def mongoize(object) | ||
| case object | ||
| when BSON::Vector then BSON::Binary.from_vector(object) | ||
| when BSON::Binary then object | ||
| end | ||
| end |
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| context 'when given a vector BSON::Binary' do | ||
| it 'returns it unchanged' do | ||
| binary = BSON::Binary.from_vector(vector) | ||
| expect(BSON::Vector.mongoize(binary)).to eq(binary) | ||
| end | ||
| end | ||
|
|
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| context 'when given nil' do | ||
| it 'returns nil' do | ||
| expect(BSON::Vector.mongoize(nil)).to be_nil | ||
| end | ||
| end |
jamis
approved these changes
Jul 1, 2026
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MONGOID-5918
Adds official support for using
BSON::Vectoras a Mongoid field type. A field declaredtype: BSON::Vectoris now stored as a BSON binary of the vector subtype (subtype 9) and read back as aBSON::Vector, preservingdtypeandpadding.Previously this did not work:
BSON::Vectorsubclasses::Array, so without a dedicated extension it was mongoized through theArrayextension and persisted as a plain BSON array, losing the vector subtype.Changes
Implementation:
lib/mongoid/extensions/vector.rb(new) — type-casting forBSON::Vector:#mongoize/.mongoize:BSON::Vector→BSON::Binary.from_vector(vector subtype); a vectorBSON::Binaryis returned unchanged;nilfornil, a plain array, or any other uncastable value..demongoize: a vectorBSON::Binary→BSON::Vector; otherwisenil.if defined?(BSON::Vector)so Mongoid still loads on bson-ruby < 5.1, which predatesBSON::Vector.lib/mongoid/extensions.rb— require the new extension.Tests:
spec/mongoid/extensions/vector_spec.rb(new) — unit coverage formongoize/demongoize(includingnil, non-vector binary, plain array, and uncastable inputs), a regression guard that a vector is not mongoized via theArrayextension, and a persistence round-trip (acrossint8,float32, andpacked_bit) asserting the stored value is a vector-subtype binary that reads back as an equivalentBSON::Vector. Gated withmin_bson_version '5.1'and a guarded model so the bson 4.14/5.0 CI jobs stay green.Scope
Querying by an exact vector value (
where(embedding: vector)) is intentionally not supported. BecauseBSON::VectorsubclassesArray, the criteria selector treats it as a list of elements rather than a scalar, so the value would not match the stored binary. Similarity queries on vector fields use Atlas Vector Search ($vectorSearch), not exact-matchwhere. This is documented in the extension.Test plan
bundle exec rspec spec/mongoid/extensions/vector_spec.rb— 22 examples, 0 failures (live replica set)binary_spec.rb,array_spec.rb,mongoizable_spec.rb— 148 examples, 0 failuresbundle exec rubocop lib/mongoid/extensions/vector.rb lib/mongoid/extensions.rb spec/mongoid/extensions/vector_spec.rb— no offenses