fix: register embedding functions in extension SQL and install v2.0.0 schema in Docker

[jjohare]

Summary

• Fix version mismatch: Dockerfile now copies both ruvector--0.1.0.sql and ruvector--2.0.0.sql into the image. Previously only 0.1.0 was installed, but ruvector.control declares default_version = '2.0.0', causing CREATE EXTENSION ruvector to fail with "no installation script for version 2.0.0".

• Register embedding functions: Both extension SQL files had a comment stub for embedding functions instead of actual CREATE FUNCTION declarations. The Docker build compiles fastembed into ruvector.so via --features embeddings, and all _wrapper symbols are present in the binary, but PostgreSQL never knew about them. Replaced the stubs with 11 function declarations (10 C functions + 1 SQL convenience function).

• Fix volatility markers: embeddings.sql incorrectly marked stateful functions (ruvector_load_model, ruvector_embedding_models, ruvector_embed, etc.) as IMMUTABLE. Changed to VOLATILE where the function loads models, mutates cache state, or returns mutable results. Only ruvector_embedding_dims remains IMMUTABLE (pure dimension lookup).

• Add ruvector_embed_vec() convenience function: ruvector_embed() returns real[] (PostgreSQL array format {...}), but the ruvector type expects bracket notation [...]. This SQL wrapper handles the conversion so users can do ruvector_embed_vec('some text')::ruvector(384) in a single call.

• Add embedding smoke test to init.sql: Tests ruvector_default_model() and ruvector_embedding_dims() during container initialization.

Root Cause

The extension SQL files (ruvector--0.1.0.sql / ruvector--2.0.0.sql) were hand-crafted as a fallback because cargo pgrx schema is unreliable in Docker. The embedding function declarations from sql/embeddings.sql were never merged into these files — they only contained a note saying "build with --features embeddings", even though the Dockerfile does exactly that.

Files Changed

File	Change
crates/ruvector-postgres/Dockerfile	Copy both 0.1.0 and 2.0.0 SQL; verify embedding functions in build
crates/ruvector-postgres/sql/ruvector--0.1.0.sql	Replace embedding comment stub with 11 function declarations
crates/ruvector-postgres/sql/ruvector--2.0.0.sql	Replace embedding comment stub with 11 function declarations
crates/ruvector-postgres/sql/embeddings.sql	Fix IMMUTABLE→VOLATILE, add ruvector_embed_vec(), add _wrapper docs
crates/ruvector-postgres/docker/init.sql	Add embedding function smoke test

Test plan

• Build Docker image: docker build -f crates/ruvector-postgres/Dockerfile -t ruvector-postgres .
• Verify CREATE EXTENSION ruvector succeeds (v2.0.0)
• Verify SELECT ruvector_embed('hello world') returns 384-dim real[]
• Verify SELECT ruvector_embed_vec('hello world') returns ruvector type
• Verify SELECT * FROM ruvector_embedding_models() lists 6 models
• Verify SELECT ruvector_default_model() returns all-MiniLM-L6-v2
• Verify init.sql smoke tests pass in container logs

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