Make index tests more robust against non-deterministic results

The #select_value method returns a value of one randomly chosen column,
which can sometimes be a NULL value even if the row itself exist.

bin/lhm-test-all.sh

@@ -1,6 +1,10 @@
 #!/bin/sh
 
-for gemfile in gemfiles/*.gemfile; do
-  BUNDLE_GEMFILE=$gemfile bundle install
-  BUNDLE_GEMFILE=$gemfile bundle exec rake
+for gemfile in gemfiles/*.gemfile
+do
+  if !(BUNDLE_GEMFILE=$gemfile bundle install &&
+       BUNDLE_GEMFILE=$gemfile bundle exec rake)
+  then
+    exit 1
+  fi
 done

spec/integration/integration_helper.rb

@@ -53,6 +53,7 @@ def execute(*args)
       connection.execute(*args)
     rescue ActiveRecord::StatementInvalid => e
       if (retries -= 1) > 0 && e.message =~ /Table '.*?' doesn't exist/
+        sleep 0.1
         retry
       else
         raise
@@ -122,7 +123,7 @@ def index_on_columns?(table_name, cols, type = :non_unique)
   def index?(table_name, key_name, type = :non_unique)
     non_unique = type == :non_unique ? 1 : 0
 
-    !!select_value(%Q<
+    !!select_one(%Q<
       show indexes in #{ table_name }
      where key_name = '#{ key_name }'
        and non_unique = #{ non_unique }