To find out about boolean logic, take a look here: http://www.laynetworks.com/Boolean%20Algebra.htm
Where I work, we took the SIS toolkit from Berkeley and did a simplification of the where clause as if it was a Boolean integrated circuit. Of course, you may get answers that you do not expect if the data has NULL values, so you can turn that simplification option off also. After Boolean simplification, this: SELECT Products.RECORD_NUMBER , Products.PRODUCTID , Products.PRODUCTNAME , Products.PRODUCTPRICE , Products.PRODUCTKEYWORDS , Products.PRODUCTGROUPID FROM Products WHERE ( ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND ( Products.PRODUCTGROUPID < 10 ) AND ( ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND ( Products.PRODUCTGROUPID < 10 ) OR ( ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) OR ( ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTGROUPID < 10 ) ) OR ( ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) OR ( ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTGROUPID < 10 ) ) AND ( ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) OR ( ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTGROUPID < 10 ) ) OR ( ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) OR ( ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTGROUPID < 10 ) ) OR ( ( Products.PRODUCTPRICE > 14 ) OR ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND ( ( Products.PRODUCTPRICE > 14 ) OR ( Products.PRODUCTGROUPID < 10 ) ) AND ( ( Products.PRODUCTPRICE > 14 ) OR ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND ( ( Products.PRODUCTPRICE > 14 ) OR ( Products.PRODUCTGROUPID < 10 ) ) OR ( ( Products.PRODUCTPRICE > 14 ) OR ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) OR ( Products.PRODUCTGROUPID < 10 ) AND ( ( Products.PRODUCTPRICE > 14 ) OR ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) OR ( Products.PRODUCTGROUPID < 10 ) OR ( NOT ( Products.PRODUCTPRICE > 14 ) AND NOT ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) OR ( NOT ( Products.PRODUCTPRICE > 14 ) AND NOT ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND ( NOT ( Products.PRODUCTPRICE > 14 ) OR NOT ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND ( NOT ( Products.PRODUCTPRICE > 14 ) OR NOT ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND ( ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND ( Products.PRODUCTGROUPID < 10 ) OR ( ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND ( Products.PRODUCTGROUPID < 10 ) OR ( ( Products.PRODUCTPRICE > 14 ) OR ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) OR ( Products.PRODUCTGROUPID < 10 ) OR ( ( Products.PRODUCTPRICE > 14 ) OR ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) OR ( Products.PRODUCTGROUPID < 10 ) AND ( NOT ( Products.PRODUCTPRICE > 14 ) OR NOT ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND ( NOT ( Products.PRODUCTPRICE > 14 ) OR ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND ( NOT ( Products.PRODUCTPRICE > 14 ) OR NOT ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND ( NOT ( Products.PRODUCTPRICE > 14 ) OR ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND ( Products.PRODUCTPRICE > 14 ) AND ( ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND ( Products.PRODUCTGROUPID < 10 ) OR ( Products.PRODUCTPRICE > 14 ) AND ( ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND ( Products.PRODUCTGROUPID < 10 ) OR ( Products.PRODUCTPRICE > 14 ) AND ( ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND ( Products.PRODUCTGROUPID < 10 ) OR ( Products.PRODUCTPRICE > 14 ) AND ( ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND ( Products.PRODUCTGROUPID < 10 ) OR ( Products.PRODUCTPRICE > 14 ) AND ( ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) OR ( Products.PRODUCTGROUPID < 10 ) OR ( Products.PRODUCTPRICE > 14 ) AND ( ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) OR ( Products.PRODUCTGROUPID < 10 ) AND ( Products.PRODUCTPRICE > 14 ) AND ( ( Products.PRODUCTPRICE > 14 ) OR ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND ( Products.PRODUCTPRICE > 14 ) AND ( ( Products.PRODUCTPRICE > 14 ) OR ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) OR ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTKEYWORDS ) Like '%coffee%' AND ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTKEYWORDS ) Like '%coffee%' OR ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTKEYWORDS ) Like '%coffee%' OR ( Products.PRODUCTPRICE > 14 ) AND NOT ( Products.PRODUCTKEYWORDS ) Like '%coffee%' AND ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTKEYWORDS ) Like '%coffee%' OR ( Products.PRODUCTPRICE > 14 ) AND NOT ( Products.PRODUCTKEYWORDS ) Like '%coffee%' OR ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTPRICE > 14 ) OR ( Products.PRODUCTPRICE > 14 ) AND 0 AND ( Products.PRODUCTPRICE > 14 ) AND 0 OR ( Products.PRODUCTPRICE > 14 ) AND 1 AND ( Products.PRODUCTPRICE > 14 ) AND 1 OR ( Products.PRODUCTPRICE > 14 ) AND NOT ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTPRICE > 14 ) AND NOT ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTPRICE > 14 ) OR ( ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) OR ( Products.PRODUCTGROUPID < 10 ) OR ( Products.PRODUCTPRICE > 14 ) OR ( ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) OR ( Products.PRODUCTGROUPID < 10 ) OR ( Products.PRODUCTPRICE > 14 ) OR ( ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND ( Products.PRODUCTGROUPID < 10 ) OR ( Products.PRODUCTPRICE > 14 ) OR ( ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND ( Products.PRODUCTGROUPID < 10 ) OR ( Products.PRODUCTPRICE > 14 ) OR ( ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) OR ( Products.PRODUCTGROUPID < 10 ) OR ( Products.PRODUCTPRICE > 14 ) OR ( ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) OR ( Products.PRODUCTGROUPID < 10 ) OR ( Products.PRODUCTPRICE > 14 ) OR ( ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) OR ( Products.PRODUCTPRICE > 14 ) OR ( ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND ( Products.PRODUCTPRICE > 14 ) OR ( Products.PRODUCTKEYWORDS ) Like '%coffee%' OR ( Products.PRODUCTPRICE > 14 ) OR ( Products.PRODUCTKEYWORDS ) Like '%coffee%' OR ( Products.PRODUCTPRICE > 14 ) OR ( Products.PRODUCTPRICE > 14 ) OR ( Products.PRODUCTPRICE > 14 ) OR ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTKEYWORDS ) Like '%coffee%' AND ( Products.PRODUCTPRICE > 14 ) OR ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTKEYWORDS ) Like '%coffee%' AND ( Products.PRODUCTPRICE > 14 ) OR ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTPRICE > 14 ) OR 0 OR ( Products.PRODUCTPRICE > 14 ) OR 0 OR ( Products.PRODUCTPRICE > 14 ) OR 1 OR ( Products.PRODUCTPRICE > 14 ) OR 1 OR ( Products.PRODUCTPRICE > 14 ) OR NOT ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTPRICE > 14 ) OR NOT ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTKEYWORDS ) Like '%coffee%' OR ( Products.PRODUCTPRICE > 14 ) OR NOT ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTKEYWORDS ) Like '%coffee%' OR ( Products.PRODUCTPRICE > 14 ) OR NOT ( Products.PRODUCTPRICE > 14 ) OR NOT ( ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND NOT ( ( Products.PRODUCTPRICE > 14 ) AND ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND NOT ( ( Products.PRODUCTPRICE > 14 ) OR ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) OR NOT ( ( Products.PRODUCTPRICE > 14 ) OR ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) OR NOT ( NOT ( Products.PRODUCTPRICE > 14 ) ) OR NOT ( NOT ( Products.PRODUCTPRICE > 14 ) ) AND NOT ( Products.PRODUCTPRICE > 14 ) AND ( ( Products.PRODUCTPRICE > 14 ) OR NOT ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND NOT ( Products.PRODUCTPRICE > 14 ) AND ( ( Products.PRODUCTPRICE > 14 ) OR NOT ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND NOT ( Products.PRODUCTPRICE > 14 ) AND NOT ( Products.PRODUCTKEYWORDS ) Like '%coffee%' OR NOT ( Products.PRODUCTPRICE > 14 ) AND NOT ( Products.PRODUCTKEYWORDS ) Like '%coffee%' OR NOT ( Products.PRODUCTPRICE > 14 ) OR NOT ( Products.PRODUCTKEYWORDS ) Like '%coffee%' AND NOT ( Products.PRODUCTPRICE > 14 ) OR NOT ( Products.PRODUCTKEYWORDS ) Like '%coffee%' AND NOT ( ( Products.PRODUCTPRICE > 14 ) OR ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) AND NOT ( Products.PRODUCTPRICE > 14 ) OR NOT ( Products.PRODUCTKEYWORDS ) Like '%coffee%' AND NOT ( ( Products.PRODUCTPRICE > 14 ) OR ( Products.PRODUCTKEYWORDS ) Like '%coffee%' ) OR NOT ( Products.PRODUCTPRICE > 14 ) OR NOT ( Products.PRODUCTKEYWORDS ) Like '%coffee%' Becomes this: SELECT t1.RECORD_NUMBER , t1.PRODUCTID , t1.PRODUCTNAME , t1.PRODUCTPRICE , t1.PRODUCTKEYWORDS , t1.PRODUCTGROUPID FROM Products t1 > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:pgsql-hackers- > [EMAIL PROTECTED] On Behalf Of Tatsuo Ishii > Sent: Tuesday, September 13, 2005 4:02 PM > To: pgsql-hackers@postgresql.org > Subject: [HACKERS] inverse OR distributive law? > > Hi, > > I have been looking around optimizer's code and found a comment: > > /* > * process_duplicate_ors > * Given a list of exprs which are ORed together, try to apply > * the inverse OR distributive law. > > Anybody enlighten what "inverse OR distributive law" is? > -- > SRA OSS, Inc. Japan > Tatsuo Ishii > > ---------------------------(end of broadcast)--------------------------- > TIP 4: Have you searched our list archives? > > http://archives.postgresql.org ---------------------------(end of broadcast)--------------------------- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
