fix(pgvector): use the correct lowering for cosineDistance

The lowering for `cosineDistance` function used `1 - ({{self}} <=>
{{arg0}})` template, which is the formula for cosine similarity, not
cosine distance. `<=>` itself is the cosine distance operator in
pgvector.

Author: aqrln

packages/2-sql/4-lanes/sql-builder-new/test/integration/extension-functions.test.ts

@@ -4,24 +4,24 @@ import { collect, setupIntegrationTest } from './setup';
 describe('integration: extension functions', () => {
   const { db } = setupIntegrationTest();
 
-  it('cosineDistance computes similarity for identical vectors', async () => {
+  it('cosineDistance computes distance for identical vectors', async () => {
     const row = await db()
       .posts.select('id')
-      .select('similarity', (f, fns) => fns.cosineDistance(f.embedding, [1, 0, 0]))
+      .select('distance', (f, fns) => fns.cosineDistance(f.embedding, [1, 0, 0]))
       .where((f, fns) => fns.eq(f.id, 1))
       .first();
     expect(row).not.toBeNull();
-    // template: 1 - (self <=> arg0), identical vectors → 1 - 0 = 1
-    expect(row!.similarity).toBeCloseTo(1, 5);
+    // template: self <=> arg0, identical vectors → distance = 0
+    expect(row!.distance).toBeCloseTo(0, 5);
   });
 
   it('cosineDistance filters in WHERE', async () => {
-    // post 1 has embedding [1,0,0] → similarity to [1,0,0] is 1.0
-    // post 3 has embedding [0,0,1] → similarity to [1,0,0] is ~0 (orthogonal)
+    // post 1 has embedding [1,0,0] → distance to [1,0,0] is 0.0
+    // post 3 has embedding [0,0,1] → distance to [1,0,0] is ~1 (orthogonal)
     const rows = await collect(
       db()
         .posts.select('id')
-        .where((f, fns) => fns.gt(fns.cosineDistance(f.embedding, [1, 0, 0]), 0.5))
+        .where((f, fns) => fns.lt(fns.cosineDistance(f.embedding, [1, 0, 0]), 0.5))
         .all(),
     );
     expect(rows.length).toBeGreaterThan(0);

packages/2-sql/4-lanes/sql-builder-new/test/runtime/functions.test.ts

@@ -266,7 +266,7 @@ describe('extension functions', () => {
         lowering: {
           targetFamily: 'sql' as const,
           strategy: 'function' as const,
-          template: '1 - ({{self}} <=> {{arg0}})',
+          template: '{{self}} <=> {{arg0}}',
         },
       },
     };

packages/3-extensions/pgvector/README.md

@@ -164,7 +164,7 @@ Computes the cosine distance between two vectors.
 
 **Signature**: `cosineDistance(rhs: number[] | vector): number`
 
-**SQL**: Uses the pgvector `<=>` operator: `1 - (vector1 <=> vector2)`
+**SQL**: Uses the pgvector `<=>` operator: `vector1 <=> vector2`
 
 **Example**:
 ```typescript

packages/3-extensions/pgvector/src/core/descriptor-meta.ts

@@ -6,7 +6,7 @@ const pgvectorTypeId = 'pg/vector@1' as const;
 const cosineLowering = {
   targetFamily: 'sql',
   strategy: 'function',
-  template: '1 - ({{self}} <=> {{arg0}})',
+  template: '{{self}} <=> {{arg0}}',
 } as const;
 
 const cosineDistanceOperation = Object.freeze({
@@ -32,7 +32,7 @@ export const pgvectorQueryOperations: readonly QueryOperationDescriptor[] = [
     lowering: {
       targetFamily: 'sql',
       strategy: 'function',
-      template: '1 - ({{self}} <=> {{arg0}})',
+      template: '{{self}} <=> {{arg0}}',
     },
   },
 ];

packages/3-extensions/pgvector/test/manifest.test.ts

@@ -44,7 +44,7 @@ describe('pgvector descriptor', () => {
     expect(cosineDistanceOp?.lowering).toEqual({
       targetFamily: 'sql',
       strategy: 'function',
-      template: '1 - ({{self}} <=> {{arg0}})',
+      template: '{{self}} <=> {{arg0}}',
     });
   });
 

packages/3-extensions/pgvector/test/operations.test.ts

@@ -35,7 +35,7 @@ describe('pgvector operations', () => {
     expect(cosineDistanceOp?.lowering).toEqual({
       targetFamily: 'sql',
       strategy: 'function',
-      template: '1 - ({{self}} <=> {{arg0}})',
+      template: '{{self}} <=> {{arg0}}',
     });
   });