Fix connection search path being reset

RESET ALL is reseting too many parameters, we should reset only the
parameter we just set, namely statement_timeout

https://gitlab.com/gitlab-org/gitlab/-/issues/337813

Changelog: fixed

lib/gitlab/database/migration_helpers.rb

@@ -341,9 +341,9 @@ module Gitlab
       # - Per connection (requires a cleanup after the execution)
       #
       # When using a per connection disable statement, code must be inside
-      # a block so we can automatically execute `RESET ALL` after block finishes
+      # a block so we can automatically execute `RESET statement_timeout` after block finishes
       # otherwise the statement will still be disabled until connection is dropped
-      # or `RESET ALL` is executed
+      # or `RESET statement_timeout` is executed
       def disable_statement_timeout
         if block_given?
           if statement_timeout_disabled?
@@ -357,7 +357,7 @@ module Gitlab
 
               yield
             ensure
-              execute('RESET ALL')
+              execute('RESET statement_timeout')
             end
           end
         else

spec/support/shared_examples/lib/gitlab/migration_helpers_shared_examples.rb

@@ -14,10 +14,10 @@ RSpec.shared_examples 'performs validation' do |validation_option|
   it 'performs validation' do
     expect(model).to receive(:disable_statement_timeout).and_call_original
     expect(model).to receive(:statement_timeout_disabled?).and_return(false)
-    expect(model).to receive(:execute).with(/statement_timeout/)
+    expect(model).to receive(:execute).with(/SET statement_timeout TO/)
     expect(model).to receive(:execute).ordered.with(/NOT VALID/)
     expect(model).to receive(:execute).ordered.with(/VALIDATE CONSTRAINT/)
-    expect(model).to receive(:execute).ordered.with(/RESET ALL/)
+    expect(model).to receive(:execute).ordered.with(/RESET statement_timeout/)
 
     model.add_concurrent_foreign_key(*args, **options.merge(validation_option))
   end