Thread: Pagination of search results
Hi, I'm writing a search engine, the results of which will displayed in blocks of 25, paginated. I will also display the number of records found (1-25 of 345). I'm trying to determine the most efficient way to implement this. Since the session is dropped after the script is terminated, I'm ruling our cursors. Also, cursors would prevent me from retrieving the total number of records potentially returned from a search, and so I couldn't display the correct number of page links. Also, this would require persistent connections, which I'd like to avoid for a number of reasons. The best I've come up with is "SELECT b.*, c.cnt FROM table AS b, (SELECT COUNT(1) AS cnt FROM table WHERE <LOTS OF CLAUSES>) AS c WHERE <SAME LOT OF CLAUSES> LIMIT 25 OFFSET 0" However this means that the query is essentially getting executed twice for each page. Is there any better way of implementing this? All advice gratefully received. Kind Regards, Neil Saunders.
I think that this is the way. You need at first time know the number of recrods at first, then you need that's records to show. ----- Mensaje original ----- De: Neil Saunders <n.j.saunders@gmail.com> Fecha: Miércoles, Noviembre 23, 2005 1:14 pm Asunto: [PHP] Pagination of search results > Hi, > > I'm writing a search engine, the results of which will displayed in > blocks of 25, paginated. I will also display the number of records > found (1-25 of 345). > > I'm trying to determine the most efficient way to implement this. > Since the session is dropped after the script is terminated, I'm > ruling our cursors. Also, cursors would prevent me from retrieving the > total number of records potentially returned from a search, and so I > couldn't display the correct number of page links. Also, this would > require persistent connections, which I'd like to avoid for a number > of reasons. > > The best I've come up with is "SELECT b.*, c.cnt FROM table AS b, > (SELECT COUNT(1) AS cnt FROM table WHERE <LOTS OF CLAUSES>) AS c WHERE > <SAME LOT OF CLAUSES> LIMIT 25 OFFSET 0" > > However this means that the query is essentially getting executed > twice for each page. > > Is there any better way of implementing this? All advice gratefully > received. > Kind Regards, > > Neil Saunders. > > ---------------------------(end of broadcast)----------------------- > ---- > TIP 6: explain analyze is your friend >
on 11/23/05 9:14 AM, n.j.saunders@gmail.com purportedly said: > I'm writing a search engine, the results of which will displayed in > blocks of 25, paginated. I will also display the number of records > found (1-25 of 345). > > I'm trying to determine the most efficient way to implement this. > Since the session is dropped after the script is terminated, I'm > ruling our cursors. Also, cursors would prevent me from retrieving the > total number of records potentially returned from a search, and so I > couldn't display the correct number of page links. Also, this would > require persistent connections, which I'd like to avoid for a number > of reasons. > > The best I've come up with is "SELECT b.*, c.cnt FROM table AS b, > (SELECT COUNT(1) AS cnt FROM table WHERE <LOTS OF CLAUSES>) AS c WHERE > <SAME LOT OF CLAUSES> LIMIT 25 OFFSET 0" > > However this means that the query is essentially getting executed > twice for each page. > > Is there any better way of implementing this? All advice gratefully received. As I understand the query planner in PG optimizes for LIMIT, but may not be able to work in all situations or may require some tweaking for best performance. If performance is a big issue, the way I have found (that has the least overall overhead) is to have the application cache results--either in memory (stored as part of the PHP session) or as a temporary text file tied to the session. For the latter, the tricky bit is making sure to remove old files, and there are several ways this can be done depending on anticipated volume and storage issues. For the former, you need to watch out for memory issues. I tend to prefer the latter technique unless I can guarantee that results will be small (including accumulated storage from multiple simultaneous sessions). Best regards, Keary Suska Esoteritech, Inc. "Demystifying technology for your home or business"
Get the count once and store it in a session. ----- Original Message ----- From: "Neil Saunders" <n.j.saunders@gmail.com> To: <pgsql-php@postgresql.org> Sent: Wednesday, November 23, 2005 8:14 AM Subject: [PHP] Pagination of search results Hi, I'm writing a search engine, the results of which will displayed in blocks of 25, paginated. I will also display the number of records found (1-25 of 345). I'm trying to determine the most efficient way to implement this. Since the session is dropped after the script is terminated, I'm ruling our cursors. Also, cursors would prevent me from retrieving the total number of records potentially returned from a search, and so I couldn't display the correct number of page links. Also, this would require persistent connections, which I'd like to avoid for a number of reasons. The best I've come up with is "SELECT b.*, c.cnt FROM table AS b, (SELECT COUNT(1) AS cnt FROM table WHERE <LOTS OF CLAUSES>) AS c WHERE <SAME LOT OF CLAUSES> LIMIT 25 OFFSET 0" However this means that the query is essentially getting executed twice for each page. Is there any better way of implementing this? All advice gratefully received. Kind Regards, Neil Saunders. ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
If you sotre the count into a session, maybe you show incorrect information. It's possible that someone insert a new record when you are changing from one page to another. Sorry, my english it's very bad. ----- Original Message ----- From: "Cstdenis" <cstdenis@voicio.com> To: "Neil Saunders" <n.j.saunders@gmail.com>; <pgsql-php@postgresql.org> Sent: Saturday, November 26, 2005 5:59 AM Subject: Re: [PHP] Pagination of search results > Get the count once and store it in a session. > > ----- Original Message ----- > From: "Neil Saunders" <n.j.saunders@gmail.com> > To: <pgsql-php@postgresql.org> > Sent: Wednesday, November 23, 2005 8:14 AM > Subject: [PHP] Pagination of search results > > > Hi, > > I'm writing a search engine, the results of which will displayed in > blocks of 25, paginated. I will also display the number of records > found (1-25 of 345). > > I'm trying to determine the most efficient way to implement this. > Since the session is dropped after the script is terminated, I'm > ruling our cursors. Also, cursors would prevent me from retrieving the > total number of records potentially returned from a search, and so I > couldn't display the correct number of page links. Also, this would > require persistent connections, which I'd like to avoid for a number > of reasons. > > The best I've come up with is "SELECT b.*, c.cnt FROM table AS b, > (SELECT COUNT(1) AS cnt FROM table WHERE <LOTS OF CLAUSES>) AS c WHERE > <SAME LOT OF CLAUSES> LIMIT 25 OFFSET 0" > > However this means that the query is essentially getting executed > twice for each page. > > Is there any better way of implementing this? All advice gratefully > received. > > Kind Regards, > > Neil Saunders. > > ---------------------------(end of broadcast)--------------------------- > TIP 6: explain analyze is your friend > > > > ---------------------------(end of broadcast)--------------------------- > TIP 5: don't forget to increase your free space map settings > >