Merge pull request rsim#2719 from yahonda/evict-stale-prepared-statements-on-ddl

Evict stale prepared statements on DDL via clear_table_columns_cache

Author: yahonda

lib/active_record/connection_adapters/oracle_enhanced_adapter.rb

@@ -902,9 +902,24 @@ def column_definitions(table_name)
       end
 
       def clear_table_columns_cache(table_name)
-        @columns_cache[table_name.to_s] = nil
-        @trigger_assigned_pk_cache.delete(table_name.to_s)
+        table_name = table_name.to_s
+        @columns_cache[table_name] = nil
+        @trigger_assigned_pk_cache.delete(table_name)
+        evict_prepared_statements_for(table_name)
+      end
+
+      def evict_prepared_statements_for(table_name) # :nodoc:
+        return unless prepared_statements?
+        return unless @statements
+
+        quoted_table_name = quote_table_name(table_name)
+        keys_to_delete = []
+        @statements.each do |sql, _stmt|
+          keys_to_delete << sql if sql.include?(quoted_table_name)
+        end
+        keys_to_delete.each { |sql| @statements.delete(sql) }
       end
+      private :evict_prepared_statements_for
 
       # Returns +[pk, sequence]+ for single-column PKs; +nil+ for composite or
       # missing PKs (composite PKs are introspected via +primary_keys+).

spec/active_record/connection_adapters/oracle_enhanced/schema_statements_spec.rb

@@ -1628,6 +1628,54 @@ class ::TestPost < ActiveRecord::Base
     end
   end
 
+  describe "prepared statement cache eviction on DDL" do
+    before(:each) do
+      schema_define do
+        create_table :test_evict, force: true do |t|
+          t.string :name
+          t.integer :extra
+        end
+      end
+    end
+
+    after(:each) do
+      schema_define do
+        drop_table :test_evict, if_exists: true
+      end
+      ActiveRecord::Base.clear_cache!
+    end
+
+    def cached_prepared_sqls_for(table_name)
+      pool = @conn.instance_variable_get(:@statements)
+      return [] unless pool
+      pool.map { |sql, _| sql }.select { |sql| sql.include?(@conn.send(:quote_table_name, table_name)) }
+    end
+
+    it "removes cached prepared statements after a column is dropped" do
+      klass = Class.new(ActiveRecord::Base) { self.table_name = :test_evict }
+      klass.create!(name: "before-ddl", extra: 1)
+      expect(cached_prepared_sqls_for(:test_evict)).not_to be_empty
+
+      schema_define do
+        remove_column :test_evict, :extra
+      end
+
+      expect(cached_prepared_sqls_for(:test_evict)).to be_empty
+    end
+
+    it "removes cached prepared statements after the table is dropped" do
+      klass = Class.new(ActiveRecord::Base) { self.table_name = :test_evict }
+      klass.create!(name: "before-drop", extra: 1)
+      expect(cached_prepared_sqls_for(:test_evict)).not_to be_empty
+
+      schema_define do
+        drop_table :test_evict, if_exists: true
+      end
+
+      expect(cached_prepared_sqls_for(:test_evict)).to be_empty
+    end
+  end
+
   describe "alter columns with column cache" do
     include LoggerSpecHelper