Re: [GENERAL] question on parallelism
On Thu, Jan 2, 2014 at 2:29 PM, Chris Travers chris.trav...@gmail.com wrote: On Wed, Jan 1, 2014 at 7:35 PM, Andrew McIntyre amcint...@m-m.com wrote: does postgres have this capability? specifically local intrapartition? http://pic.dhe.ibm.com/infocenter/db2luw/v10r5/topic/com.ibm.db2.luw.admin.partition.doc/doc/c0004557.html Nope. Here's a quick breakdown of what is done in parallel and what is done sequentially in PostgreSQL. Separate queries run in parallel, and can piggy back on eachother's sequential scans. In essence all of the work that is done in parallelism affects parallel queries. There is no intra-query parallelism however. This means that partitioning doesn't generally help here (although sequential scans on the same partition by different queries can run in parallel with good results, a single query cannot run several scans on different partitions in parallel). If you need this sort of feature you are going to either need to go to a related product (like Postgres-XC) or you are going to need to have some other layer that can do the parallelism. In the case of XC, it is worth noting that a query can take advantage of parallelism on a sequential scan only roughly for sharded tables. In the case of replicated table, query is usually simply pushed to one singke remote node, making the scan occur on this single node. Regards, -- Michael -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
[GENERAL] question on parallelism
does postgres have this capability? specifically local intrapartition? http://pic.dhe.ibm.com/infocenter/db2luw/v10r5/topic/com.ibm.db2.luw.admin.partition.doc/doc/c0004557.html sorry for all the newbie pg questions... -- personal Signature Andrew McIntyre amcint...@m-m.com mailto:amcint...@m-m.com http://www.mindspring.com/~amcintyr/resume.htm http://www.mindspring.com/%7Eamcintyr/resume.htm
Re: [GENERAL] question on parallelism
On Wed, Jan 1, 2014 at 7:35 PM, Andrew McIntyre amcint...@m-m.com wrote: does postgres have this capability? specifically local intrapartition? http://pic.dhe.ibm.com/infocenter/db2luw/v10r5/topic/com.ibm.db2.luw.admin.partition.doc/doc/c0004557.html Nope. Here's a quick breakdown of what is done in parallel and what is done sequentially in PostgreSQL. Separate queries run in parallel, and can piggy back on eachother's sequential scans. In essence all of the work that is done in parallelism affects parallel queries. There is no intra-query parallelism however. This means that partitioning doesn't generally help here (although sequential scans on the same partition by different queries can run in parallel with good results, a single query cannot run several scans on different partitions in parallel). If you need this sort of feature you are going to either need to go to a related product (like Postgres-XC) or you are going to need to have some other layer that can do the parallelism. Best Wishes, Chris Travers sorry for all the newbie pg questions... -- -- Andrew McIntyre amcint...@m-m.com http://www.mindspring.com/~amcintyr/resume.htm -- -- Best Wishes, Chris Travers Efficito: Hosted Accounting and ERP. Robust and Flexible. No vendor lock-in. http://www.efficito.com/learn_more.shtml
