Logstash JDBC Input Plugin: Informix DB Windowing Support Proof-of-Concept

jdbc-informix-windowing.diff

diff --git a/lib/logstash/plugin_mixins/jdbc.rb b/lib/logstash/plugin_mixins/jdbc.rb
index c9bc547..934a4f1 100644
--- a/lib/logstash/plugin_mixins/jdbc.rb
+++ b/lib/logstash/plugin_mixins/jdbc.rb
@@ -162,6 +162,7 @@ module LogStash::PluginMixins::Jdbc
       raise LogStash::ConfigurationError, "#{e}. #{message}"
     end
     @database = jdbc_connect()
+    @database.extension(:informix_windowing)
     @database.extension(:pagination)
     if @jdbc_default_timezone
       @database.extension(:named_timezones)
@@ -311,3 +312,21 @@ module LogStash::PluginMixins::Jdbc
     end
   end
 end
+
+# In the Informix SQL dialect, windowing functions are sub-clauses on the `SELECT` clause, not stand-alone clauses.
+# This extension _replaces_ the dataset's select-statement limit-clause builder with a no-op implementation, and adds
+# the approrpriate `SKIP X` and `FIRST Y` sub-clauses to the select-statment's select clause.
+module InformixWindowing
+  private
+
+  def select_select_sql(sql)
+    super(sql)
+    sql << " SKIP #{@opts[:offset]}" if @opts[:offset]
+    sql << " FIRST #{@opts[:limit]}" if @opts[:limit]
+  end
+
+  def select_limit_sql(sql)
+    # no-op
+  end
+end
+Sequel::Dataset.register_extension(:informix_windowing, InformixWindowing)

Diff above is Apache2-licensed, following that of the Logstash JDBC Input Plugin it is meant to be applied to.