perf(session): Avoid select when canceling session

internal/db/schema/migrations/oss/postgres/29/01_cancel_session_null_fkey.up.sql

@@ -9,6 +9,7 @@ drop function cancel_session(in sessionId text);
 -- Sessions can progress directly to terminated without going through the canceling state
 -- cancel_session will insert a cancel state for the session, if there's isn't
 -- a canceled or terminated state already.  It's used by cancel_session_with_null_fk.
+-- Replaced in 91/07_cancel_session_trigger.up.sql
 create function cancel_session(in sessionId text) returns void
 as $$
 declare

internal/db/schema/migrations/oss/postgres/91/07_cancel_session_trigger.up.sql

@@ -0,0 +1,24 @@
+-- Copyright (c) HashiCorp, Inc.
+-- SPDX-License-Identifier: BUSL-1.1
+
+begin;
+
+  -- Replaces function from 29/01_cancel_session_null_fkey.up.sql
+  drop function cancel_session;
+  create function cancel_session(sessionid text) returns void
+  as $$
+  declare
+    rows_affected numeric;
+  begin
+    insert into session_state(session_id, state)
+         values              (sessionId,  'canceling');
+  exception when unique_violation
+              or foreign_key_violation
+              or check_violation
+            then
+    -- Do nothing. Any one of these violations would indicate that the session
+    -- either already is canceled, or is in a terminated state and cannot
+    -- be canceled.
+  end;
+  $$ language plpgsql;
+commit;

internal/db/sqltest/tests/session/cancel_session.sql

@@ -0,0 +1,114 @@
+-- Copyright (c) HashiCorp, Inc.
+-- SPDX-License-Identifier: BUSL-1.1
+
+begin;
+  select plan(22);
+
+  -- Canceling a terminated session should cause no errors, but should not change state.
+  prepare cancel_terminated as
+    select cancel_session('s1_____cindy');
+  -- to start s1_____cindy should have 2 states, and the terminated should be the active state.
+  select is(count(*), 2::bigint)
+    from session_state
+   where session_id = 's1_____cindy';
+  select is(count(*), 1::bigint)
+    from session_state
+   where session_id = 's1_____cindy'
+     and state = 'terminated'
+     and upper(active_time_range) is null;
+  -- now attempt to cancel
+  select lives_ok('cancel_terminated');
+  -- there should be no changes to the state
+  select is(count(*), 2::bigint)
+    from session_state
+   where session_id = 's1_____cindy';
+  select is(count(*), 1::bigint)
+    from session_state
+   where session_id = 's1_____cindy'
+     and state = 'terminated'
+     and upper(active_time_range) is null;
+
+  -- Canceling a canceling session should cause no errors, but should not change state.
+  prepare cancel_canceling as
+    select cancel_session('s1_____ciara');
+  -- to start s1_____ciara should have 2 states, and the canceling should be the active state.
+  select is(count(*), 2::bigint)
+    from session_state
+   where session_id = 's1_____ciara';
+  select is(count(*), 1::bigint)
+    from session_state
+   where session_id = 's1_____ciara'
+     and state = 'canceling'
+     and upper(active_time_range) is null;
+  -- now attempt to cancel
+  select lives_ok('cancel_canceling');
+  -- there should be no changes to the state
+  select is(count(*), 2::bigint)
+    from session_state
+   where session_id = 's1_____ciara';
+  select is(count(*), 1::bigint)
+    from session_state
+   where session_id = 's1_____ciara'
+     and state = 'canceling'
+     and upper(active_time_range) is null;
+
+  -- Canceling an active session should cause no errors and should result the state changing to canceling.
+  prepare cancel_active as
+    select cancel_session('s1_____carly');
+  -- to start s1_____carly should have 2 states, and the active should be the active state.
+  select is(count(*), 2::bigint)
+    from session_state
+   where session_id = 's1_____carly';
+  select is(count(*), 1::bigint)
+    from session_state
+   where session_id = 's1_____carly'
+     and state = 'active'
+     and upper(active_time_range) is null;
+  -- now attempt to cancel
+  select lives_ok('cancel_active');
+  -- there should be a new state and active should no long be the active state.
+  select is(count(*), 3::bigint)
+    from session_state
+   where session_id = 's1_____carly';
+  select is(count(*), 0::bigint)
+    from session_state
+   where session_id = 's1_____carly'
+     and state = 'active'
+     and upper(active_time_range) is null;
+  select is(count(*), 1::bigint)
+    from session_state
+   where session_id = 's1_____carly'
+     and state = 'canceling'
+     and upper(active_time_range) is null;
+
+  -- Canceling a pending session should cause no errors and should result the state changing to canceling.
+  prepare cancel_pending as
+    select cancel_session('s1_____clare');
+  -- to start s1_____clare should have 2 states, and the active should be the active state.
+  select is(count(*), 1::bigint)
+    from session_state
+   where session_id = 's1_____clare';
+  select is(count(*), 1::bigint)
+    from session_state
+   where session_id = 's1_____clare'
+     and state = 'pending'
+     and upper(active_time_range) is null;
+  -- now attempt to cancel
+  select lives_ok('cancel_pending');
+  -- there should be a new state and pending should no long be the active state.
+  select is(count(*), 2::bigint)
+    from session_state
+   where session_id = 's1_____clare';
+  select is(count(*), 0::bigint)
+    from session_state
+   where session_id = 's1_____clare'
+     and state = 'pending'
+     and upper(active_time_range) is null;
+  select is(count(*), 1::bigint)
+    from session_state
+   where session_id = 's1_____clare'
+     and state = 'canceling'
+     and upper(active_time_range) is null;
+
+  select * from finish();
+rollback;