Обсуждение: \dt+ sizes don't include TOAST data
The sizes displayed by \dt+ in version 8.4.2 do not take TOAST tables into account, presumably because the pg_relation_size does not reflect that, either. I think this is a bit surprising. From a user perspective, these are part of the table storage (I understand that the indices might be a different story, but TOAST table are a fairly deep implementation detail and should perhaps be hidden here). -- Florian Weimer <fweimer@bfk.de> BFK edv-consulting GmbH http://www.bfk.de/ Kriegsstraße 100 tel: +49-721-96201-1 D-76133 Karlsruhe fax: +49-721-96201-99
Florian Weimer wrote: > The sizes displayed by \dt+ in version 8.4.2 do not take TOAST tables > into account, presumably because the pg_relation_size does not reflect > that, either. I think this is a bit surprising. From a user > perspective, these are part of the table storage (I understand that > the indices might be a different story, but TOAST table are a fairly > deep implementation detail and should perhaps be hidden here). > As of last week there's a new pg_table_size available that does what you want here: http://archives.postgresql.org/pgsql-committers/2010-01/msg00288.php I don't believe \dt+ has been updated yet to use that though; that's worth considering for a minute, not sure anybody thought about it yet. -- Greg Smith 2ndQuadrant Baltimore, MD PostgreSQL Training, Services and Support greg@2ndQuadrant.com www.2ndQuadrant.com
Greg Smith <greg@2ndquadrant.com> writes: > Florian Weimer wrote: >> The sizes displayed by \dt+ in version 8.4.2 do not take TOAST tables >> into account, presumably because the pg_relation_size does not reflect >> that, either. I think this is a bit surprising. From a user >> perspective, these are part of the table storage (I understand that >> the indices might be a different story, but TOAST table are a fairly >> deep implementation detail and should perhaps be hidden here). > As of last week there's a new pg_table_size available that does what you > want here: > http://archives.postgresql.org/pgsql-committers/2010-01/msg00288.php > I don't believe \dt+ has been updated yet to use that though; that's > worth considering for a minute, not sure anybody thought about it yet. We could only use pg_table_size against a backend >= 9.0, which would mean that the displayed results mean something different depending on which backend version psql is being used with. That's not necessarily a deal-breaker, but it does seem a bit evil. An alternative worth thinking about is to make it use pg_total_relation_size instead of pg_relation_size. That's available, with similar semantics, in all versions that have pg_relation_size either (ie, >= 8.1). Also, this is arguably more nearly the right thing since at the level of \dt+ I think people would expect indexes to get folded in too. regards, tom lane
Tom Lane wrote: > Greg Smith <greg@2ndquadrant.com> writes: > > Florian Weimer wrote: > >> The sizes displayed by \dt+ in version 8.4.2 do not take TOAST tables > >> into account, presumably because the pg_relation_size does not reflect > >> that, either. I think this is a bit surprising. From a user > >> perspective, these are part of the table storage (I understand that > >> the indices might be a different story, but TOAST table are a fairly > >> deep implementation detail and should perhaps be hidden here). > > > As of last week there's a new pg_table_size available that does what you > > want here: > > http://archives.postgresql.org/pgsql-committers/2010-01/msg00288.php > > > I don't believe \dt+ has been updated yet to use that though; that's > > worth considering for a minute, not sure anybody thought about it yet. > > We could only use pg_table_size against a backend >= 9.0, which would > mean that the displayed results mean something different depending on > which backend version psql is being used with. That's not necessarily > a deal-breaker, but it does seem a bit evil. Perhaps we can emulate pg_table_size on earlier server versions, using a query which provides the sum of table plus toast items. It would be a bit slower, but the normal case of using the same server version would be fast. -- Alvaro Herrera http://www.CommandPrompt.com/ The PostgreSQL Company - Command Prompt, Inc.
Alvaro Herrera wrote: > Tom Lane wrote: > > Greg Smith <greg@2ndquadrant.com> writes: > > > Florian Weimer wrote: > > >> The sizes displayed by \dt+ in version 8.4.2 do not take TOAST tables > > >> into account, presumably because the pg_relation_size does not reflect > > >> that, either. I think this is a bit surprising. From a user > > >> perspective, these are part of the table storage (I understand that > > >> the indices might be a different story, but TOAST table are a fairly > > >> deep implementation detail and should perhaps be hidden here). > > > > > As of last week there's a new pg_table_size available that does what you > > > want here: > > > http://archives.postgresql.org/pgsql-committers/2010-01/msg00288.php > > > > > I don't believe \dt+ has been updated yet to use that though; that's > > > worth considering for a minute, not sure anybody thought about it yet. > > > > We could only use pg_table_size against a backend >= 9.0, which would > > mean that the displayed results mean something different depending on > > which backend version psql is being used with. That's not necessarily > > a deal-breaker, but it does seem a bit evil. > > Perhaps we can emulate pg_table_size on earlier server versions, using a > query which provides the sum of table plus toast items. It would be a > bit slower, but the normal case of using the same server version would > be fast. Added to TODO: Consider showing TOAST and index sizes in \dt+ * http://archives.postgresql.org/pgsql-general/2010-01/msg00912.php -- Bruce Momjian <bruce@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + If your life is a hard drive, Christ can be your backup. +