sql: support pgvector

[jordanlewis]

The pgvector Postgres extension is a popular extension that adds support for vector similarity indexing and search.

This issue tracks adding support to CockroachDB.

Types

• vector type
• bit type
• halfvec type
• sparsevec type

Operators

• + operator
• - operator
• * operator
• || operator (concatenate)
• <-> operator (l2 distance)
• <#> operator (negative inner product)
• <=> operator (cosine distance)
• <+> operator (taxicab/l1 distance)
• <~> operator (Hamming distance for bit type)
• <%> operator (Jaccard distance for bit type)

Builtin functions

• cosine_distance function
• inner_product function
• l2_distance function
• l1_distance function
• l2_normalize function
• vector_dims function
• vector_norm function
• subvector function
• binary_quantize function
• hamming_distance function
• jaccard_distance function
• avg aggregate function
• sum aggregate function

Indexing

• ivfflat index
• hnsw index
• Acceleration of <->, <#> and <=> operators depending on which opclass is chosen at index creation time (vector_l2_ops, vector_ip_ops, vector_cosine_ops)

Configuration options

• ivfflat.probes - defines # of centroid lists to search during lookup

Jira issue: CRDB-37252