[HACKERS] static genericcostestimate
Hi, The genericcostestimate function is currently static. This limits the development of new access methods as loadable modules without touching pgsql sources. Currently I have to include a copy of the function in the module, which is obviously too bad. Is there any reason to keep this function static ? Thanks ---(end of broadcast)--- TIP 2: you can get off all lists at once with the unregister command (send unregister YourEmailAddressHere to [EMAIL PROTECTED])
Re: [HACKERS] static genericcostestimate
Tom Lane wrote: Ramy M. Hassan [EMAIL PROTECTED] writes: The genericcostestimate function is currently static. This limits the development of new access methods as loadable modules without touching pgsql sources. Currently I have to include a copy of the function in the module, which is obviously too bad. Is there any reason to keep this function static ? Is it really of much use for your access method? It's such a crude hack that I didn't want to encourage people to use it ... it is really just a stopgap until someone gets around to thinking harder about the actual access behavior of the existing index AMs. BTW, what are you working on? I had no idea that anyone was experimenting with new index methods. I am currently working on porting SP-GiST to postgresql. SP-GiST is an adaptation of GiST to support space partitioning trees ( http://www.cs.purdue.edu/homes/aref/dbsystems_files/SP-GiST/ ) The current standalone SP-GiST implementation is based on libgist v1.0 from berkeley ( http://gist.cs.berkeley.edu/libgistv1/ ) The core SP-GiST is being implemented as module to be loaded before any spgist extention module. I am expecting the first alpha release early of May. Currently, there is no effort done in cost estimation for SP-GiST, so the genericcostestimate seams to be ok for now. regards, tom lane ---(end of broadcast)--- TIP 6: Have you searched our list archives? http://archives.postgresql.org
Re: [HACKERS] sp-gist porting to postgreSQL
I believe that it is still possible to have several index access methods for the same type and the same operations. But this requires that each index access method has its own tuple in the pg_am relation and therefore postgresql recognizes it by itself. But this is not the case with GiST based indices. They are all recognized by postgresql as same index access method, and from here comes the limitation. Also, I think GiST and SP-GiST are better viewed as index classes not as indices by themselves. So may be it is more logical to say: CREATE INDEX index_name ON table_name USING spgist_trie(field) Where spgist_trie is an spgist based index instance. Than to say: CREATE INDEX index_name ON table_name USING spgist(field) And depend on the operator classes to define the required support methods for the trie function. I am not sure I have a complete vision, but this is what I see. I would appreciate your opinions regarding to this design issue. Thanks Ramy -Original Message- From: Oleg Bartunov [mailto:[EMAIL PROTECTED] Sent: Wednesday, November 10, 2004 5:21 AM To: Ramy M. Hassan Cc: 'Pgsql Hackers'; 'Teodor Sigaev'; 'Walid G. Aref' Subject: RE: sp-gist porting to postgreSQL On Wed, 10 Nov 2004, Ramy M. Hassan wrote: Oleg, Thanks for your prompt reply. Actually, I am able to create a new access method for testing and add an operator class for the type integer using the new access method. Then created a table with two integer fields, one indexed using the new access method and the other using a btree index, and everything is ok so far. Even using EXPLAIN statement for queries show that the indexes are used correctly as they should. I am using postgresql version 8.0.0beta3 from CVS. I was wrong, Ramy. You could have several indices for the same type as soon as they support different operations. I don't know if it's possible to have them for the same operation but for different conditions. Thanks Ramy -Original Message- From: Oleg Bartunov [mailto:[EMAIL PROTECTED] Sent: Wednesday, November 10, 2004 12:35 AM To: Ramy M. Hassan; Pgsql Hackers Cc: Teodor Sigaev; Walid G. Aref Subject: Re: sp-gist porting to postgreSQL Ramy, glad to hear from you ! AFAIK, posgresql doesnt' supports several indices for the same type. I think this is a problem of optimizer. Probably other hackers know better. I forward your message to -hackers mailing list which is a relevant place for GiST discussion. regards, Oleg On Tue, 9 Nov 2004, Ramy M. Hassan wrote: Dear Oleg and Teodor, Thanks for offering help. I have a design question for now. Currently in the postgresql GiST implementation, I noticed that the way to have a GiST based index is to define an operator class for a certain type using GiST index. There is no new index type defined from the point of view of postgresql ( nothing is added to pg_am ). This means that for a certain type there could only be one GiST based index. I mean that there is no way in the same server to use gist to implement an xtree index and a ytree for the same type even if they index different fields in different relations. is that correct ? What about doing it the other way ( I am talking about SP-GiST now ) , by providing the extension writer with an API to use it to instantiate a standalone SP-GiST based index ( for example trie index ) that has a record in the pg_am relation. In my point of view this would give more flexibility, and also would not require the extension writer to learn the postgresql API ( maybe oneday SP-GiST will be ported to another database engine ) he will just need to learn the SP-GiST API which will propably be less amount of study (and this is what GiST and SP-GiST is all about if I correctly understand ). Please let me know your opinions regarding to this. Thanks Ramy Regards, Oleg _ Oleg Bartunov, sci.researcher, hostmaster of AstroNet, Sternberg Astronomical Institute, Moscow University (Russia) Internet: [EMAIL PROTECTED], http://www.sai.msu.su/~megera/ phone: +007(095)939-16-83, +007(095)939-23-83 Regards, Oleg _ Oleg Bartunov, sci.researcher, hostmaster of AstroNet, Sternberg Astronomical Institute, Moscow University (Russia) Internet: [EMAIL PROTECTED], http://www.sai.msu.su/~megera/ phone: +007(095)939-16-83, +007(095)939-23-83 ---(end of broadcast)--- TIP 8: explain analyze is your friend
Re: [HACKERS] sp-gist porting to postgreSQL
On Wed, 10 Nov 2004, Oleg Bartunov wrote: On Wed, 10 Nov 2004, Ramy M. Hassan wrote: I believe that it is still possible to have several index access methods for the same type and the same operations. But this requires that each index access method has its own tuple in the pg_am relation and therefore postgresql recognizes it by itself. But this is not the case with GiST based indices. They are all recognized by postgresql as same index access method, and from here comes the limitation. It's possible, see contrib/intarray, for example. You can specify opclass in CREATE INDEX command: CREATE INDEX text_idx on test__int using gist ( a gist__int_ops ); CREATE INDEX text_idx2 on test__int using gist ( a gist__intbig_ops ); Here gist__int_ops and gist__intbig_ops are different opclasses for the same type and intended to use with different cardinality. The problem is how to use them (indices) automatically, how planner/optimizer could select which indices to use. This is great. I didn't know that. Thanks. Also, I think GiST and SP-GiST are better viewed as index classes not as indices by themselves. So may be it is more logical to say: CREATE INDEX index_name ON table_name USING spgist_trie(field) Where spgist_trie is an spgist based index instance. Than to say: CREATE INDEX index_name ON table_name USING spgist(field) And depend on the operator classes to define the required support methods for the trie function. why not use existed syntax ? CREATE INDEX index_name ON table_name USING spgist (fiels trie_ops) That's ok now. The only concern now is the portability of the extensions. Currently Are there any plans to introduce GiST to some other DBMS ? If yes, then I think all GiST based indexes will have to be rewritten or atleast modified to a great extent, as they depend on postgresql API and how index access methods work in postgresql. Do you see any value in defining an SP-GiST API for the extensions to completely isolate the extensions code from postgresql ? Such isolation will require that SP-GiST code loads the extensions instead of relying on postgresql to do that so it will no longer be a matter of operator classes that defines extension. I am not sure I have a complete vision, but this is what I see. I would appreciate your opinions regarding to this design issue. Teodor is rather busy right now, but he certainly knows better GiST internals, so we'll wait his comments. Thanks Ramy -Original Message- From: Oleg Bartunov [mailto:[EMAIL PROTECTED] Sent: Wednesday, November 10, 2004 5:21 AM To: Ramy M. Hassan Cc: 'Pgsql Hackers'; 'Teodor Sigaev'; 'Walid G. Aref' Subject: RE: sp-gist porting to postgreSQL On Wed, 10 Nov 2004, Ramy M. Hassan wrote: Oleg, Thanks for your prompt reply. Actually, I am able to create a new access method for testing and add an operator class for the type integer using the new access method. Then created a table with two integer fields, one indexed using the new access method and the other using a btree index, and everything is ok so far. Even using EXPLAIN statement for queries show that the indexes are used correctly as they should. I am using postgresql version 8.0.0beta3 from CVS. I was wrong, Ramy. You could have several indices for the same type as soon as they support different operations. I don't know if it's possible to have them for the same operation but for different conditions. Thanks Ramy -Original Message- From: Oleg Bartunov [mailto:[EMAIL PROTECTED] Sent: Wednesday, November 10, 2004 12:35 AM To: Ramy M. Hassan; Pgsql Hackers Cc: Teodor Sigaev; Walid G. Aref Subject: Re: sp-gist porting to postgreSQL Ramy, glad to hear from you ! AFAIK, posgresql doesnt' supports several indices for the same type. I think this is a problem of optimizer. Probably other hackers know better. I forward your message to -hackers mailing list which is a relevant place for GiST discussion. regards, Oleg On Tue, 9 Nov 2004, Ramy M. Hassan wrote: Dear Oleg and Teodor, Thanks for offering help. I have a design question for now. Currently in the postgresql GiST implementation, I noticed that the way to have a GiST based index is to define an operator class for a certain type using GiST index. There is no new index type defined from the point of view of postgresql ( nothing is added to pg_am ). This means that for a certain type there could only be one GiST based index. I mean that there is no way in the same server to use gist to implement an xtree index and a ytree for the same type even if they index different fields in different relations. is that correct ? What about doing it the other way ( I am talking about SP-GiST now ) , by providing the extension writer with an API to use it to instantiate a standalone SP-GiST based index ( for example trie index ) that has a record in the pg_am relation. In my point of view this would give more flexibility, and also would not require the extension writer to learn the postgresql API ( maybe oneday SP-GiST
Re: [HACKERS] sp-gist porting to postgreSQL
Oleg, Thanks for your prompt reply. Actually, I am able to create a new access method for testing and add an operator class for the type integer using the new access method. Then created a table with two integer fields, one indexed using the new access method and the other using a btree index, and everything is ok so far. Even using EXPLAIN statement for queries show that the indexes are used correctly as they should. I am using postgresql version 8.0.0beta3 from CVS. Thanks Ramy -Original Message- From: Oleg Bartunov [mailto:[EMAIL PROTECTED] Sent: Wednesday, November 10, 2004 12:35 AM To: Ramy M. Hassan; Pgsql Hackers Cc: Teodor Sigaev; Walid G. Aref Subject: Re: sp-gist porting to postgreSQL Ramy, glad to hear from you ! AFAIK, posgresql doesnt' supports several indices for the same type. I think this is a problem of optimizer. Probably other hackers know better. I forward your message to -hackers mailing list which is a relevant place for GiST discussion. regards, Oleg On Tue, 9 Nov 2004, Ramy M. Hassan wrote: Dear Oleg and Teodor, Thanks for offering help. I have a design question for now. Currently in the postgresql GiST implementation, I noticed that the way to have a GiST based index is to define an operator class for a certain type using GiST index. There is no new index type defined from the point of view of postgresql ( nothing is added to pg_am ). This means that for a certain type there could only be one GiST based index. I mean that there is no way in the same server to use gist to implement an xtree index and a ytree for the same type even if they index different fields in different relations. is that correct ? What about doing it the other way ( I am talking about SP-GiST now ) , by providing the extension writer with an API to use it to instantiate a standalone SP-GiST based index ( for example trie index ) that has a record in the pg_am relation. In my point of view this would give more flexibility, and also would not require the extension writer to learn the postgresql API ( maybe oneday SP-GiST will be ported to another database engine ) he will just need to learn the SP-GiST API which will propably be less amount of study (and this is what GiST and SP-GiST is all about if I correctly understand ). Please let me know your opinions regarding to this. Thanks Ramy Regards, Oleg _ Oleg Bartunov, sci.researcher, hostmaster of AstroNet, Sternberg Astronomical Institute, Moscow University (Russia) Internet: [EMAIL PROTECTED], http://www.sai.msu.su/~megera/ phone: +007(095)939-16-83, +007(095)939-23-83 ---(end of broadcast)--- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
[HACKERS] implementation guide
Hi all, Is there any updated implementation guide for postgresql 7.x ? I've been using the postgres95 guide at http://pluto.iis.nsk.su/postgres95/impl-guide/ but it is incomplete and also it does not reflect the current state of the code. I can see many structures were modified since postgres95. Thanks Ramy ---(end of broadcast)--- TIP 7: don't forget to increase your free space map settings
