add test for vector search in ATTACHED db

Author: sivukhin

libsql-sqlite3/test/libsql_vector_index.test

@@ -508,3 +508,24 @@ do_test vector-errors {
   {vector index(search): third parameter (k) must be an integer, but float value were provided}
   {vector index(insert): dimensions are different: 1 != 3}
 }]
+
+
+do_test vector-index-attach-setup {
+  forcedelete test2.db
+  forcedelete test2.db-journal
+  sqlite3 db2 test2.db
+
+  execsql {
+    CREATE TABLE t_attach(e FLOAT32(3));
+    CREATE INDEX t_attach_idx ON t_attach(libsql_vector_idx(e));
+    INSERT INTO t_attach VALUES (vector('[1,2,3]'));
+    INSERT INTO t_attach VALUES (vector('[2,3,4]'));
+    INSERT INTO t_attach VALUES (vector('[3,4,5]'));
+    INSERT INTO t_attach VALUES (vector('[4,5,6]'));
+  } db2
+} {}
+
+do_execsql_test vector-index-attach-query {
+  ATTACH DATABASE 'test2.db' AS t;
+  SELECT * FROM vector_top_k('t.t_attach_idx', vector('[3,4,5]'), 4);
+} {3 4 2 1}