Add support and tests for install-time schema relocation

Our extension cannot be fully relocatable since its objects span
multiple schemas (we have _lantern_internal schema)
It can be (and as of this commit) is install-time relocatable
so it can be installed on a custom schema, different from the default
one. See 38.17.2 in the link below for details
https://www.postgresql.org/docs/current/extend-extensions.html#EXTEND-EXTENSIONS-RELOCATION

Note: access methods in postgres are not schema-qualified so they are
always available globally, regardless of the schema on which the
extension is installed
https://www.postgresql.org/docs/current/sql-create-access-method.html

cmake/lantern.control.template

@@ -1,4 +1,4 @@
-comment = 'LanternDB: Fast vector embedding processing in Postgres'
+comment = 'Lantern: Fast vector embedding processing in Postgres'
 default_version = '@LANTERNDB_VERSION@'
 module_pathname = '$libdir/lantern'
-relocatable = true
+relocatable = false

sql/lantern.sql

@@ -29,8 +29,9 @@ CREATE OPERATOR <-> (
 	COMMUTATOR = '<->'
 );
 
+CREATE SCHEMA _lantern_internal;
 -- operator classes
-CREATE OR REPLACE FUNCTION _create_ldb_operator_classes(access_method_name TEXT) RETURNS BOOLEAN AS $$
+CREATE OR REPLACE FUNCTION _lantern_internal._create_ldb_operator_classes(access_method_name TEXT) RETURNS BOOLEAN AS $$
 DECLARE
     dist_l2sq_ops TEXT;
     dist_cos_ops TEXT;
@@ -107,13 +108,13 @@ BEGIN
 
 
 	IF hnsw_am_exists THEN
-		PERFORM _create_ldb_operator_classes('lantern_hnsw');
+		PERFORM _lantern_internal._create_ldb_operator_classes('lantern_hnsw');
 		RAISE WARNING 'Access method(index type) "hnsw" already exists. Creating lantern_hnsw access method';
 	ELSE
 		-- create access method
 		CREATE ACCESS METHOD hnsw TYPE INDEX HANDLER hnsw_handler;
 		COMMENT ON ACCESS METHOD hnsw IS 'LanternDB access method for vector embeddings, based on the hnsw algorithm';
-		PERFORM _create_ldb_operator_classes('hnsw');
+		PERFORM _lantern_internal._create_ldb_operator_classes('hnsw');
 	END IF;
 END;
 $BODY$

test/expected/ext_relocation.out

@@ -0,0 +1,109 @@
+\ir utils/small_world_array.sql
+CREATE TABLE small_world (
+    id VARCHAR(3),
+    b BOOLEAN,
+    v REAL[3]
+);
+INSERT INTO small_world (id, b, v) VALUES
+    ('000', TRUE,  '{0,0,0}'),
+    ('001', TRUE,  '{0,0,1}'),
+    ('010', FALSE, '{0,1,0}'),
+    ('011', TRUE,  '{0,1,1}'),
+    ('100', FALSE, '{1,0,0}'),
+    ('101', FALSE, '{1,0,1}'),
+    ('110', FALSE, '{1,1,0}'),
+    ('111', TRUE,  '{1,1,1}');
+DROP EXTENSION lantern;
+\set ON_ERROR_STOP off
+-- make sure the extension was dropped.
+CREATE INDEX ON small_world USING hnsw (v) WITH (dim=3);
+ERROR:  access method "hnsw" does not exist
+\set ON_ERROR_STOP on
+-- test creating lantern on different schemas
+CREATE SCHEMA schema1;
+CREATE SCHEMA schema2;
+CREATE EXTENSION lantern WITH SCHEMA schema1;
+-- show all the extension functions and operators
+SELECT ne.nspname AS extschema, p.proname, np.nspname AS proschema
+FROM pg_catalog.pg_extension AS e
+    INNER JOIN pg_catalog.pg_depend AS d ON (d.refobjid = e.oid)
+    INNER JOIN pg_catalog.pg_proc AS p ON (p.oid = d.objid)
+    INNER JOIN pg_catalog.pg_namespace AS ne ON (ne.oid = e.extnamespace)
+    INNER JOIN pg_catalog.pg_namespace AS np ON (np.oid = p.pronamespace)
+WHERE d.deptype = 'e' AND e.extname = 'lantern'
+ORDER BY 1, 3;
+ extschema |           proname            |     proschema     
+-----------+------------------------------+-------------------
+ schema1   | _create_ldb_operator_classes | _lantern_internal
+ schema1   | ldb_generic_dist             | schema1
+ schema1   | ldb_generic_dist             | schema1
+ schema1   | hnsw_handler                 | schema1
+ schema1   | cos_dist                     | schema1
+ schema1   | hamming_dist                 | schema1
+ schema1   | l2sq_dist                    | schema1
+(7 rows)
+
+-- show all the extension operators
+SELECT ne.nspname AS extschema, op.oprname, np.nspname AS proschema
+FROM pg_catalog.pg_extension AS e
+    INNER JOIN pg_catalog.pg_depend AS d ON (d.refobjid = e.oid)
+    INNER JOIN pg_catalog.pg_operator AS op ON (op.oid = d.objid)
+    INNER JOIN pg_catalog.pg_namespace AS ne ON (ne.oid = e.extnamespace)
+    INNER JOIN pg_catalog.pg_namespace AS np ON (np.oid = op.oprnamespace)
+WHERE d.deptype = 'e' AND e.extname = 'lantern'
+ORDER BY 1, 3;
+ extschema | oprname | proschema 
+-----------+---------+-----------
+ schema1   | <->     | schema1
+ schema1   | <->     | schema1
+(2 rows)
+
+SET search_path TO public, schema1;
+-- extension function is accessible
+SELECT l2sq_dist(ARRAY[1.0, 2.0, 3.0], ARRAY[4.0, 5.0, 6.0]);
+ l2sq_dist 
+-----------
+        27
+(1 row)
+
+CREATE INDEX hnsw_index ON small_world USING hnsw(v) WITH (dim=3);
+INFO:  done init usearch index
+INFO:  inserted 8 elements
+INFO:  done saving 8 vectors
+\set ON_ERROR_STOP off
+-- lantern does not support relocation.
+-- Postgres will not allow it to support this since its objects span over more than one schema
+ALTER EXTENSION lantern SET SCHEMA schema2;
+ERROR:  extension "lantern" does not support SET SCHEMA
+\set ON_ERROR_STOP on
+SELECT ne.nspname AS extschema, op.oprname, np.nspname AS proschema
+FROM pg_catalog.pg_extension AS e
+    INNER JOIN pg_catalog.pg_depend AS d ON (d.refobjid = e.oid)
+    INNER JOIN pg_catalog.pg_operator AS op ON (op.oid = d.objid)
+    INNER JOIN pg_catalog.pg_namespace AS ne ON (ne.oid = e.extnamespace)
+    INNER JOIN pg_catalog.pg_namespace AS np ON (np.oid = op.oprnamespace)
+WHERE d.deptype = 'e' AND e.extname = 'lantern'
+ORDER BY 1, 3;
+ extschema | oprname | proschema 
+-----------+---------+-----------
+ schema1   | <->     | schema1
+ schema1   | <->     | schema1
+(2 rows)
+
+SET search_path TO public, schema2;
+--extension access method is still accessible since access methods are not schema-qualified
+CREATE INDEX hnsw_index2 ON small_world USING hnsw(v) WITH (dim=3);
+INFO:  done init usearch index
+INFO:  inserted 8 elements
+INFO:  done saving 8 vectors
+\set ON_ERROR_STOP off
+-- extension function cannot be found without schema-qualification
+SELECT l2sq_dist(ARRAY[1.0, 2.0, 3.0], ARRAY[4.0, 5.0, 6.0]);
+ERROR:  function l2sq_dist(numeric[], numeric[]) does not exist at character 8
+\set ON_ERROR_STOP on
+SELECT schema1.l2sq_dist(ARRAY[1.0, 2.0, 3.0], ARRAY[4.0, 5.0, 6.0]);
+ l2sq_dist 
+-----------
+        27
+(1 row)
+

test/schedule.txt

@@ -4,4 +4,4 @@
 # - 'test' lines may have multiple space-separated tests. All tests in a single 'test' line will be run in parallel
 
 test_pgvector: hnsw_vector
-test: hnsw_config hnsw_correct hnsw_create hnsw_create_expr hnsw_dist_func hnsw_insert hnsw_select hnsw_todo hnsw_index_from_file hnsw_cost_estimate
+test: hnsw_config hnsw_correct hnsw_create hnsw_create_expr hnsw_dist_func hnsw_insert hnsw_select hnsw_todo hnsw_index_from_file hnsw_cost_estimate ext_relocation

test/sql/ext_relocation.sql

@@ -0,0 +1,64 @@
+\ir utils/small_world_array.sql
+
+DROP EXTENSION lantern;
+\set ON_ERROR_STOP off
+-- make sure the extension was dropped.
+CREATE INDEX ON small_world USING hnsw (v) WITH (dim=3);
+\set ON_ERROR_STOP on
+
+-- test creating lantern on different schemas
+CREATE SCHEMA schema1;
+CREATE SCHEMA schema2;
+CREATE EXTENSION lantern WITH SCHEMA schema1;
+
+-- show all the extension functions and operators
+SELECT ne.nspname AS extschema, p.proname, np.nspname AS proschema
+FROM pg_catalog.pg_extension AS e
+    INNER JOIN pg_catalog.pg_depend AS d ON (d.refobjid = e.oid)
+    INNER JOIN pg_catalog.pg_proc AS p ON (p.oid = d.objid)
+    INNER JOIN pg_catalog.pg_namespace AS ne ON (ne.oid = e.extnamespace)
+    INNER JOIN pg_catalog.pg_namespace AS np ON (np.oid = p.pronamespace)
+WHERE d.deptype = 'e' AND e.extname = 'lantern'
+ORDER BY 1, 3;
+
+-- show all the extension operators
+SELECT ne.nspname AS extschema, op.oprname, np.nspname AS proschema
+FROM pg_catalog.pg_extension AS e
+    INNER JOIN pg_catalog.pg_depend AS d ON (d.refobjid = e.oid)
+    INNER JOIN pg_catalog.pg_operator AS op ON (op.oid = d.objid)
+    INNER JOIN pg_catalog.pg_namespace AS ne ON (ne.oid = e.extnamespace)
+    INNER JOIN pg_catalog.pg_namespace AS np ON (np.oid = op.oprnamespace)
+WHERE d.deptype = 'e' AND e.extname = 'lantern'
+ORDER BY 1, 3;
+
+SET search_path TO public, schema1;
+
+-- extension function is accessible
+SELECT l2sq_dist(ARRAY[1.0, 2.0, 3.0], ARRAY[4.0, 5.0, 6.0]);
+
+CREATE INDEX hnsw_index ON small_world USING hnsw(v) WITH (dim=3);
+
+\set ON_ERROR_STOP off
+-- lantern does not support relocation.
+-- Postgres will not allow it to support this since its objects span over more than one schema
+ALTER EXTENSION lantern SET SCHEMA schema2;
+\set ON_ERROR_STOP on
+
+SELECT ne.nspname AS extschema, op.oprname, np.nspname AS proschema
+FROM pg_catalog.pg_extension AS e
+    INNER JOIN pg_catalog.pg_depend AS d ON (d.refobjid = e.oid)
+    INNER JOIN pg_catalog.pg_operator AS op ON (op.oid = d.objid)
+    INNER JOIN pg_catalog.pg_namespace AS ne ON (ne.oid = e.extnamespace)
+    INNER JOIN pg_catalog.pg_namespace AS np ON (np.oid = op.oprnamespace)
+WHERE d.deptype = 'e' AND e.extname = 'lantern'
+ORDER BY 1, 3;
+
+SET search_path TO public, schema2;
+--extension access method is still accessible since access methods are not schema-qualified
+CREATE INDEX hnsw_index2 ON small_world USING hnsw(v) WITH (dim=3);
+
+\set ON_ERROR_STOP off
+-- extension function cannot be found without schema-qualification
+SELECT l2sq_dist(ARRAY[1.0, 2.0, 3.0], ARRAY[4.0, 5.0, 6.0]);
+\set ON_ERROR_STOP on
+SELECT schema1.l2sq_dist(ARRAY[1.0, 2.0, 3.0], ARRAY[4.0, 5.0, 6.0]);