Squashed 'vendor/ruvector/' content from commit b64c2172

git-subtree-dir: vendor/ruvector
git-subtree-split: b64c21726f2bb37286d9ee36a7869fef60cc6900

crates/ruvector-postgres/sql/ivfflat_am.sql

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+-- IVFFlat Index Access Method Installation
+-- ============================================================================
+-- Creates the ruivfflat access method for PostgreSQL
+-- Compatible with pgvector's ivfflat interface
+
+-- Create access method
+CREATE ACCESS METHOD ruivfflat TYPE INDEX HANDLER ruivfflat_handler;
+
+-- Create operator classes for different distance metrics
+
+-- L2 (Euclidean) distance operator class
+CREATE OPERATOR CLASS ruvector_ivfflat_l2_ops
+    FOR TYPE vector USING ruivfflat AS
+    OPERATOR 1 <-> (vector, vector) FOR ORDER BY float_ops,
+    FUNCTION 1 ruvector_l2_distance(vector, vector);
+
+-- Inner product distance operator class
+CREATE OPERATOR CLASS ruvector_ivfflat_ip_ops
+    FOR TYPE vector USING ruivfflat AS
+    OPERATOR 1 <#> (vector, vector) FOR ORDER BY float_ops,
+    FUNCTION 1 ruvector_ip_distance(vector, vector);
+
+-- Cosine distance operator class
+CREATE OPERATOR CLASS ruvector_ivfflat_cosine_ops
+    FOR TYPE vector USING ruivfflat AS
+    OPERATOR 1 <=> (vector, vector) FOR ORDER BY float_ops,
+    FUNCTION 1 ruvector_cosine_distance(vector, vector);
+
+-- Helper function to get IVFFlat index statistics
+CREATE OR REPLACE FUNCTION ruvector_ivfflat_stats(index_name text)
+RETURNS TABLE(
+    lists integer,
+    probes integer,
+    dimensions integer,
+    trained boolean,
+    vector_count bigint,
+    metric text
+)
+AS $$
+BEGIN
+    -- This would query the index metadata
+    -- For now, return dummy data
+    RETURN QUERY SELECT
+        100::integer as lists,
+        1::integer as probes,
+        0::integer as dimensions,
+        false::boolean as trained,
+        0::bigint as vector_count,
+        'euclidean'::text as metric;
+END;
+$$ LANGUAGE plpgsql;
+
+-- Example usage:
+--
+-- CREATE INDEX ON items USING ruivfflat (embedding vector_l2_ops)
+--   WITH (lists = 100, probes = 1);
+--
+-- CREATE INDEX ON items USING ruivfflat (embedding vector_cosine_ops)
+--   WITH (lists = 500, probes = 10);
+--
+-- SELECT * FROM ruvector_ivfflat_stats('items_embedding_idx');