Fix jdbc_fetch_size usage with postgresql

lib/logstash/plugin_mixins/jdbc/jdbc.rb

@@ -160,6 +160,7 @@ def open_jdbc_connection
       require "java"
       require "sequel"
       require "sequel/adapters/jdbc"
+      require "sequel/adapters/jdbc/transactions"
 
       Sequel.application_timezone = @plugin_timezone.to_sym
       if @drivers_loaded.false?
@@ -183,6 +184,7 @@ def open_jdbc_connection
       end
       @database = jdbc_connect()
       @database.extension(:pagination)
+      @database.extend(Sequel::JDBC::Transactions)
       if @jdbc_default_timezone
         @database.extension(:named_timezones)
         @database.timezone = @jdbc_default_timezone

lib/logstash/plugin_mixins/jdbc/statement_handler.rb

@@ -31,16 +31,20 @@ class NormalStatementHandler < StatementHandler
     # @yieldparam row [Hash{Symbol=>Object}]
     def perform_query(db, sql_last_value, jdbc_paging_enabled, jdbc_page_size)
       query = build_query(db, sql_last_value)
-      if jdbc_paging_enabled
-        query.each_page(jdbc_page_size) do |paged_dataset|
-          paged_dataset.each do |row|
+      # Execute query in transaction cause PG driver require autocommit off for set fetch count
+      # See: https://jdbc.postgresql.org/documentation/head/query.html
+      db.transaction(rollback: :always) do
+        if jdbc_paging_enabled
+          query.each_page(jdbc_page_size) do |paged_dataset|
+            paged_dataset.each do |row|
+              yield row
+            end
+          end
+        else
+          query.each do |row|
             yield row
           end
         end
-      else
-        query.each do |row|
-          yield row
-        end
       end
     end