Re: distinct values without seq scan
От | Josh Berkus |
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Тема | Re: distinct values without seq scan |
Дата | |
Msg-id | 200404070843.06144.josh@agliodbs.com обсуждение исходный текст |
Ответ на | distinct values without seq scan (Bret Hughes <bhughes@elevating.com>) |
Список | pgsql-sql |
Bret, > I have a table indexed on a char(35) field and want a query to return a > distinct list of the values in this column. Is there some syntactical > magic I can do to get these values without a sequential scan? I assume, > ( here we go again ) that these values are in the index somewhere and I > seem to recall a select DISTINCT using an index in DB2 way back when but > I may be mistaken. > > Searching the archives I found an email that indicated this was possible > in 7.4 and infact is the reason I upgraded from 7.2x. Well, leaving aside that you have a data normalization issue (these values should really be in a reference list with an FK), to take advantage of the 7.4 optimization, try: SELECT advertiser FROM logrecords GROUP BY advertiser ORDER BY advertiser; -- Josh Berkus Aglio Database Solutions San Francisco
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