Re: [PERFORM] execute cursor fetch
Hi, If anyone can help pls, I have a question abt the execution of cursor create/fetch/move , in particular about disk cost. When a cursor is created, is the whole table (with the required columns) got put into memory? otherwise how does it work? (in term of disk read and transfer?) after user issues command move/fetch, how does postgre speed up the query in compare to normal selection? Thanks a lot, regards, MT Ho __ Do you Yahoo!? Yahoo! Mail Address AutoComplete - You start. We finish. http://promotions.yahoo.com/new_mail ---(end of broadcast)--- TIP 4: Don't 'kill -9' the postmaster
Re: [PERFORM] postgresql performance with multimedia
Hi, For your streaming purposes I strongly recommend you do it in your application with the appropriate thread model. A relational database management system is not a multimedia cache. That's actually what i plan to do with postgreSQL, maybe tailor it to suit with a multimedia streaming database. Well, i could do it in the application level but i think it's also worth a try with the database itself. They are only stored in that way on initial load and if the load is done with a single process. And don't you rely on this for the future. Right now, if you ever update or delete tuples, that order changes already. does the buffer manager have any idea what table that buf belongs to? (can we add 'rel' variable to sbufdesc in buf_internals.h and update it everytime we add new entry to the buffer cahe?) And then we take in to account which relation the data in the buffer belongs to in the buf replacement algorithm or in the read-ahead policy. Also keep in mind that large values are not stored inline, but in an extra TOAST relation. This is how i store my video file: break them in to small chunks and store each part in a row of a table. regards, MThi __ Do you Yahoo!? New and Improved Yahoo! Mail - 100MB free storage! http://promotions.yahoo.com/new_mail ---(end of broadcast)--- TIP 8: explain analyze is your friend
Re: [PERFORM] postgresql performance with multimedia
Tom Lane answered to that question. The code in question does resolve localhost with getaddrinfo() and then tries to create and bind a UDP socket to all returned addresses. For some reason localhost on your system resolves to an address that is not available for bind(2). I tried to put my_ip instead of localhost in bufmng.c and it seems to work (no more complaining). However i check the pg_statio_all_tables and dont see any recorded statistic at all. (all the columns are '0') some time postmaster shut down with this err msg: LOG: statistics collector process (process_id) exited with exit code 1 i starts postmaster with this command: postmaster -i -p $PORT -D $PGDATA -k $PGDATA -N 32 -B 64 -o -s btw, what i want to ask here is does postgreSQL have any kind of read-ahead buffer implemented? 'cos it would be useful in multimedia case when we always scan the large table for continous data. Since there is no mechanism to control that data is stored contiguously in the tables, what would that be good for? i thought that rows in the table will be stored contiguously? in that case, if the user is requesting 1 row, we make sure that the continue rows are ready in the buffer pool so that when they next requested, they wont be asked to read from disk. For multimedia data, this is important 'cos data needs to be presented continuously without any waiting. thanks again for your help MT Ho __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ---(end of broadcast)--- TIP 4: Don't 'kill -9' the postmaster
Re: [PERFORM] postgresql performance with multimedia
--- Jan Wieck [EMAIL PROTECTED] wrote: On 8/17/2004 8:44 PM, my thi ho wrote: Hi, I am working on a project which explore postgresql to store multimedia data. In details, i am trying to work with the buffer management part of postgres source code. And try to improve the performance. I had search on the web but could not find much usefull information. What version of PostgreSQL are you looking at? Note that the buffer cache replacement strategy was completely changed for version 8.0, which is currently in BETA test. A description of the algorithm can be found in the README file in src/backend/storage/bufmgr. oki, Thanks for the information. I have a look at 8.0 beta, but cannot start the statistic collector. (I had post this err message before for help, but havent really got any clue to fix it) LOG: could not create IPv6 socket: Address family not supported by protocol LOG: could not bind socket for statistics collector: Cannot assign requested address LOG: disabling statistics collector for lack of working socket btw, what i want to ask here is does postgreSQL have any kind of read-ahead buffer implemented? 'cos it would be useful in multimedia case when we always scan the large table for continous data. Thanks Ho __ Do you Yahoo!? New and Improved Yahoo! Mail - 100MB free storage! http://promotions.yahoo.com/new_mail ---(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
