A minimalistic proof-of-concept PostgreSQL tuning tester tool

main.py

#!/usr/bin/python

from PyQt4 import QtCore
from PyQt4 import QtGui
from PyQt4 import uic
import sys
import psycopg2

CONN_STRING = "host='localhost' dbname='postgres' user='d33tah'"

class MainWindow(QtGui.QMainWindow):
    def __init__(self, parent=None):
        self.conn = psycopg2.connect(CONN_STRING)
        self.cur = self.conn.cursor()
        QtGui.QMainWindow.__init__(self, parent)
        self.ui = uic.loadUi('mainwindow.ui', self)
        self.ui.propertySlider.sliderChanged = self.sliderMoved
        QtCore.QObject.connect(self.ui.propertySlider,
                               QtCore.SIGNAL('valueChanged(int)'),
                               self.sliderMoved)

    def sliderMoved(self, to):
        scaled = to / 100.0 * 4
        self.ui.propertyValue.setText(str(scaled))
        self.cur.execute("SET cpu_tuple_cost='%s'" % scaled)
        sql = "EXPLAIN " + str(self.ui.queryEdit.text())
        self.cur.execute(sql)
        out = self.cur.fetchall()
        explainResults = ""
        for line in out:
            explainResults += line[0] + "\n"
        self.psqlOutput.document().setPlainText(explainResults)

def main():
    app = QtGui.QApplication(sys.argv)
    window = MainWindow()
    window.show()
    app.exec_()


if __name__ == '__main__':
    main()

mainwindow.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>757</width>
    <height>356</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <layout class="QVBoxLayout" name="verticalLayout_2">
    <item>
     <layout class="QHBoxLayout" name="horizontalLayout">
      <item>
       <widget class="QLabel" name="label">
        <property name="text">
         <string>Query:</string>
        </property>
       </widget>
      </item>
      <item>
       <widget class="QLineEdit" name="queryEdit">
        <property name="text">
         <string>SELECT  * FROM rdns</string>
        </property>
       </widget>
      </item>
     </layout>
    </item>
    <item>
     <widget class="QPlainTextEdit" name="psqlOutput">
      <property name="readOnly">
       <bool>true</bool>
      </property>
     </widget>
    </item>
    <item>
     <layout class="QHBoxLayout" name="horizontalLayout_2">
      <item>
       <widget class="QLabel" name="propertyLabel">
        <property name="text">
         <string>cpu_tuple_cost:</string>
        </property>
       </widget>
      </item>
      <item>
       <widget class="QSlider" name="propertySlider">
        <property name="orientation">
         <enum>Qt::Horizontal</enum>
        </property>
       </widget>
      </item>
      <item>
       <widget class="QLabel" name="propertyValue">
        <property name="text">
         <string>0</string>
        </property>
       </widget>
      </item>
     </layout>
    </item>
   </layout>
  </widget>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>757</width>
     <height>20</height>
    </rect>
   </property>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
 </widget>
 <resources/>
 <connections/>
</ui>