Обсуждение: What kind of performace can I expect and how to measure?
Hi all, My system is a PostgreSQL 7.4.1 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 20020903 (Red Hat Linux 8.0 3.2-7). It hasa Pentium III-733 Mhz with 512 MB ram. It is connected to my workststation (dual XEON 1700 with 1 Gb RAM) with a 100 Mbswitched network. I have a table with 31 columns, all fixed size datatypes. It contains 88393 rows. Doing a "select * from table" with PGAdminIII in it's SQL window, it takes a total of 9206 ms query runtime an a 40638 ms data retrievel runtime. Is this a reasonable time to get 88393 rows from the database? If not, what can I do to find the bottleneck (and eventually make it faster)? Groeten, Joost Kraaijeveld Askesis B.V. Molukkenstraat 14 6524NB Nijmegen tel: 024-3888063 / 06-51855277 fax: 024-3608416 e-mail: J.Kraaijeveld@Askesis.nl web: www.askesis.nl
Joost wrote: > My system is a PostgreSQL 7.4.1 on i686-pc-linux-gnu, compiled by GCC gcc > (GCC) 20020903 (Red Hat Linux 8.0 3.2-7). It has a Pentium III-733 Mhz > with 512 MB ram. It is connected to my workststation (dual XEON 1700 with > 1 Gb RAM) with a 100 Mb switched network. > > I have a table with 31 columns, all fixed size datatypes. It contains > 88393 rows. Doing a "select * from table" with PGAdmin III in it's SQL > window, it takes a total of 9206 ms query runtime an a 40638 ms data > retrievel runtime. > > Is this a reasonable time to get 88393 rows from the database? > > If not, what can I do to find the bottleneck (and eventually make it > faster)? The 9206 ms time is what the database actually spent gathering the data and sending it to you. This is non-negotiable unless you bump up hardware, etc, or fetch less data. This time usually scales linearly (or close to it) with the size of the dataset you fetch. The 40638 ms time is pgAdmin putting the data in the grid. This time spent here is dependant on your client and starts to get really nasty with large tables. Future versions of pgAdmin might be able to deal better with large datasets (cursor based fetch is one proposed solution). In the meantime, I would suggest using queries to refine your terms a little bit...(do you really need to view all 80k records at once?). Merlin
Hi Merlin, > The 9206 ms time is what the database actually spent > gathering the data and sending it to you. This is non-negotiable unless you bump up > hardware, etc, or fetch less data. This time usually scales linearly > (or close to it) with the size of the dataset you fetch. > > The 40638 ms time is pgAdmin putting the data in the grid. This time So it take PostgreSQL 9206 ms to get the data AND send it to the client. It than takes PGAdmin 40638 ms to display the data? > solution). In the meantime, I would suggest using queries to refine > your terms a little bit...(do you really need to view all 80k > records at once?). The application is build in Clarion, a 4 GL environment. We do not have any influence over the query it generates and executes. Groeten, Joost Kraaijeveld Askesis B.V. Molukkenstraat 14 6524NB Nijmegen tel: 024-3888063 / 06-51855277 fax: 024-3608416 e-mail: J.Kraaijeveld@Askesis.nl web: www.askesis.nl
> Hi Merlin, > > > The 9206 ms time is what the database actually spent > > gathering the data and sending it to you. This is non-negotiable unless > you bump up > > hardware, etc, or fetch less data. This time usually scales linearly > > (or close to it) with the size of the dataset you fetch. > > > > The 40638 ms time is pgAdmin putting the data in the grid. This time > So it take PostgreSQL 9206 ms to get the data AND send it to the client. > It than takes PGAdmin 40638 ms to display the data? That is correct. This is not a problem with pgAdmin, or postgres, but a problem with grids. Conceptually, SQL tables are an in an unordered, infinite space and grids require an ordered, finite space. All 4GLs and data managers have this problem. The real solution is to refine your query in a meaningful way (80k rows is more than a human being can deal with in a practical sense). If you can't do that, install an arbitrary limit on the result set where performance breaks down, could be 10-100k depending on various factors. To simulate a finite, ordered, dataset, pgAdmin takes all the result data and puts it in GUI controls are not designed to hold 100k rows data...this is a design compromise to allow editing. Merlin
On Mon, 2004-08-02 at 06:21, Joost Kraaijeveld wrote: > Hi all, > > My system is a PostgreSQL 7.4.1 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 20020903 (Red Hat Linux 8.0 3.2-7). Ithas a Pentium III-733 Mhz with 512 MB ram. It is connected to my workststation (dual XEON 1700 with 1 Gb RAM) with a 100Mb switched network. > > I have a table with 31 columns, all fixed size datatypes. It contains 88393 rows. Doing a "select * from table" with PGAdminIII in it's SQL window, it takes a total of 9206 ms query runtime an a 40638 ms data retrievel runtime. This means it took the backend about 9 seconds to prepare the data, and 40 or so seconds total (including the 9 I believe) for the client to retrieve and then display it. > Is this a reasonable time to get 88393 rows from the database? Depends on your row size really. I'm certain you're not CPU bound if you've only got one hard drive. Put that data on a 20 way RAID5 array and I'm sure it would come back a little quicker. > If not, what can I do to find the bottleneck (and eventually make it faster)? The bottleneck is almost always IO to start with. First, as another drive and mirror it. Then go to RAID 1+0, then add more and more drives. Read this document about performance tuning: http://www.varlena.com/varlena/GeneralBits/Tidbits/perf.html