diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 3627b8f..9ab46eb 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -12,7 +12,7 @@ jobs:
 
     strategy:
       matrix:
-        pg: [15]
+        pg: [15, 17]
 
     steps:
       - name: Start PostgreSQL ${{ matrix.pg }}
@@ -21,13 +21,13 @@ jobs:
       - name: Install build-dependencies
         run: apt-get install -y liblz4-dev libreadline-dev zlib1g-dev libzstd-dev
 
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: checkout hypopg
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           repository: 'HypoPG/hypopg'
-          ref: 'debian/1.3.1-2'
+          ref: '1.4.3'
           path: ./hypopg
 
       - name: Create tests directory
@@ -52,7 +52,7 @@ jobs:
         if: ${{ failure() }}
         run: cat regress/regression.diffs
 
-      - uses: actions/upload-artifact@v3
+      - uses: actions/upload-artifact@v4
         if: always()
         with:
           name: regression.out
diff --git a/index_advisor--0.1.2.sql b/index_advisor--0.1.1--0.1.2.sql
similarity index 100%
rename from index_advisor--0.1.2.sql
rename to index_advisor--0.1.1--0.1.2.sql
diff --git a/index_advisor--0.1.1.sql b/index_advisor--0.1.1.sql
deleted file mode 100644
index aff8083..0000000
--- a/index_advisor--0.1.1.sql
+++ /dev/null
@@ -1,159 +0,0 @@
-create or replace function index_advisor(
-    query text
-)
-    returns table  (
-        startup_cost_before jsonb,
-        startup_cost_after jsonb,
-        total_cost_before jsonb,
-        total_cost_after jsonb,
-        index_statements text[]
-    )
-    volatile
-    language plpgsql
-    as $$
-declare
-    n_args int;
-    prepared_statement_name text = 'index_advisor_working_statement';
-    hypopg_schema_name text = (select extnamespace::regnamespace::text from pg_extension where extname = 'hypopg');
-    explain_plan_statement text;
-    rec record;
-    plan_initial jsonb;
-    plan_final jsonb;
-    statements text[] = '{}';
-begin
-
-    -- Disallow multiple statements
-    if query ilike '%;%' then
-        raise exception 'query must not contain a semicolon';
-    end if;
-
-    -- Hack to support PostgREST because the prepared statement for args incorrectly defaults to text
-    query := replace(query, 'WITH pgrst_payload AS (SELECT $1 AS json_data)', 'WITH pgrst_payload AS (SELECT $1::json AS json_data)');
-
-    -- Create a prepared statement for the given query
-    deallocate all;
-    execute format('prepare %I as %s', prepared_statement_name, query);
-
-    -- Detect how many arguments are present in the prepared statement
-    n_args = (
-        select
-            coalesce(array_length(parameter_types, 1), 0)
-        from
-            pg_prepared_statements
-        where
-            name = prepared_statement_name
-        limit
-            1
-    );
-
-    -- Create a SQL statement that can be executed to collect the explain plan
-    explain_plan_statement = format(
-        'set local plan_cache_mode = force_generic_plan; explain (format json) execute %I%s',
-        --'explain (format json) execute %I%s',
-        prepared_statement_name,
-        case
-            when n_args = 0 then ''
-            else format(
-                '(%s)', array_to_string(array_fill('null'::text, array[n_args]), ',')
-            )
-        end
-    );
-
-    -- Store the query plan before any new indexes
-    execute explain_plan_statement into plan_initial;
-
-    -- Create possible indexes
-    for rec in (
-        with extension_regclass as (
-            select
-                distinct objid as oid
-            from
-                pg_depend
-            where
-                deptype = 'e'
-        )
-        select
-            pc.relnamespace::regnamespace::text as schema_name,
-            pc.relname as table_name,
-            pa.attname as column_name,
-            format(
-                'select %I.hypopg_create_index($i$create index on %I.%I(%I)$i$)',
-                hypopg_schema_name,
-                pc.relnamespace::regnamespace::text,
-                pc.relname,
-                pa.attname
-            ) hypopg_statement
-        from
-            pg_catalog.pg_class pc
-            join pg_catalog.pg_attribute pa
-                on pc.oid = pa.attrelid
-            left join extension_regclass er
-                on pc.oid = er.oid
-            left join pg_index pi
-                on pc.oid = pi.indrelid
-                and (select array_agg(x) from unnest(pi.indkey) v(x)) = array[pa.attnum]
-                and pi.indexprs is null -- ignore expression indexes
-                and pi.indpred is null -- ignore partial indexes
-        where
-            pc.relnamespace::regnamespace::text not in ( -- ignore schema list
-                'pg_catalog', 'pg_toast', 'information_schema'
-            )
-            and er.oid is null -- ignore entities owned by extensions
-            and pc.relkind in ('r', 'm') -- regular tables, and materialized views
-            and pc.relpersistence = 'p' -- permanent tables (not unlogged or temporary)
-            and pa.attnum > 0
-            and not pa.attisdropped
-            and pi.indrelid is null
-            and pa.atttypid in (20,16,1082,1184,1114,701,23,21,700,1083,2950,1700,25,18,1042,1043)
-        )
-        loop
-            -- Create the hypothetical index
-            execute rec.hypopg_statement;
-        end loop;
-
-    /*
-    for rec in select * from hypopg()
-        loop
-            raise notice '%', rec;
-        end loop;
-    */
-
-    -- Create a prepared statement for the given query
-    -- The original prepared statement MUST be dropped because its plan is cached
-    execute format('deallocate %I', prepared_statement_name);
-    execute format('prepare %I as %s', prepared_statement_name, query);
-
-    -- Store the query plan after new indexes
-    execute explain_plan_statement into plan_final;
-
-    --raise notice '%', plan_final;
-
-    -- Idenfity referenced indexes in new plan
-    execute format(
-        'select
-            coalesce(array_agg(hypopg_get_indexdef(indexrelid) order by indrelid, indkey::text), $i${}$i$::text[])
-        from
-            %I.hypopg()
-        where
-            %s ilike ($i$%%$i$ || indexname || $i$%%$i$)
-        ',
-        hypopg_schema_name,
-        quote_literal(plan_final)::text
-    ) into statements;
-
-    -- Reset all hypothetical indexes
-    perform hypopg_reset();
-
-    -- Reset prepared statements
-    deallocate all;
-
-    return query values (
-        (plan_initial -> 0 -> 'Plan' -> 'Startup Cost'),
-        (plan_final -> 0 -> 'Plan' -> 'Startup Cost'),
-        (plan_initial -> 0 -> 'Plan' -> 'Total Cost'),
-        (plan_final -> 0 -> 'Plan' -> 'Total Cost'),
-        statements::text[]
-    );
-
-end;
-$$;
diff --git a/index_advisor--0.2.0.sql b/index_advisor--0.1.2--0.2.0.sql
similarity index 98%
rename from index_advisor--0.2.0.sql
rename to index_advisor--0.1.2--0.2.0.sql
index be45cfe..8acc08a 100644
--- a/index_advisor--0.2.0.sql
+++ b/index_advisor--0.1.2--0.2.0.sql
@@ -1,4 +1,6 @@
-create or replace function index_advisor(
+drop function index_advisor(text);
+
+create function index_advisor(
     query text
 )
     returns table  (
diff --git a/test/expected/create_extension_default_version.out b/test/expected/create_extension_default_version.out
new file mode 100644
index 0000000..6dd9e09
--- /dev/null
+++ b/test/expected/create_extension_default_version.out
@@ -0,0 +1,15 @@
+begin;
+    -- Unversioned CREATE EXTENSION must resolve through the full upgrade
+    -- chain (0.1.0 -> 0.1.1 -> 0.1.2 -> default_version), since only 0.1.0
+    -- exists as a standalone install script - everything after that is only
+    -- reachable via incremental upgrade scripts. Confirms the chain is
+    -- unbroken end to end, not just reachable via an explicit version pin.
+    create extension index_advisor cascade;
+NOTICE:  installing required extension "hypopg"
+    select extversion from pg_extension where extname = 'index_advisor';
+ extversion 
+------------
+ 0.2.0
+(1 row)
+
+rollback;
diff --git a/test/expected/upgrade_from_oldest_version.out b/test/expected/upgrade_from_oldest_version.out
new file mode 100644
index 0000000..55345e1
--- /dev/null
+++ b/test/expected/upgrade_from_oldest_version.out
@@ -0,0 +1,29 @@
+begin;
+    -- Simulates a project that installed index_advisor at its very first
+    -- version and later runs ALTER EXTENSION ... UPDATE (e.g. during a
+    -- Postgres major-version upgrade, or a manual extension update) -
+    -- exercises the full 0.1.0 -> 0.1.1 -> 0.1.2 -> default_version upgrade
+    -- chain end to end, including the 0.1.2->default_version return-type
+    -- change (drop + recreate), not just a fresh install pinned at one
+    -- version.
+    create extension index_advisor version '0.1.0' cascade;
+NOTICE:  installing required extension "hypopg"
+    alter extension index_advisor update;
+    select extversion from pg_extension where extname = 'index_advisor';
+ extversion 
+------------
+ 0.2.0
+(1 row)
+
+    create table public.book(
+        id int
+    );
+    select index_advisor($$
+        select * from book where id = $1
+    $$);
+                                  index_advisor                                  
+---------------------------------------------------------------------------------
+ (0.00,4.13,41.88,14.83,"{""CREATE INDEX ON public.book USING btree (id)""}",{})
+(1 row)
+
+rollback;
diff --git a/test/sql/create_extension_default_version.sql b/test/sql/create_extension_default_version.sql
new file mode 100644
index 0000000..bb5497a
--- /dev/null
+++ b/test/sql/create_extension_default_version.sql
@@ -0,0 +1,12 @@
+begin;
+
+    -- Unversioned CREATE EXTENSION must resolve through the full upgrade
+    -- chain (0.1.0 -> 0.1.1 -> 0.1.2 -> default_version), since only 0.1.0
+    -- exists as a standalone install script - everything after that is only
+    -- reachable via incremental upgrade scripts. Confirms the chain is
+    -- unbroken end to end, not just reachable via an explicit version pin.
+    create extension index_advisor cascade;
+
+    select extversion from pg_extension where extname = 'index_advisor';
+
+rollback;
diff --git a/test/sql/upgrade_from_oldest_version.sql b/test/sql/upgrade_from_oldest_version.sql
new file mode 100644
index 0000000..0293c0d
--- /dev/null
+++ b/test/sql/upgrade_from_oldest_version.sql
@@ -0,0 +1,24 @@
+begin;
+
+    -- Simulates a project that installed index_advisor at its very first
+    -- version and later runs ALTER EXTENSION ... UPDATE (e.g. during a
+    -- Postgres major-version upgrade, or a manual extension update) -
+    -- exercises the full 0.1.0 -> 0.1.1 -> 0.1.2 -> default_version upgrade
+    -- chain end to end, including the 0.1.2->default_version return-type
+    -- change (drop + recreate), not just a fresh install pinned at one
+    -- version.
+    create extension index_advisor version '0.1.0' cascade;
+
+    alter extension index_advisor update;
+
+    select extversion from pg_extension where extname = 'index_advisor';
+
+    create table public.book(
+        id int
+    );
+
+    select index_advisor($$
+        select * from book where id = $1
+    $$);
+
+rollback;