Thread: Concurrent Reindex on Primary Key for large table
I have a large table with about 60 million rows, everyday I add 3-4 million, remove 3-4 million and update 1-2 million. I have a script that reindexes concurrently a couple of times a week, since I see significant bloat. I have autovac on and the settings are below. I can't concurrently reindex the primary key, since there can be only one on a table. I can't take the table offline to do a drop/recreate. I assumed the autovac would take care of the bloat there, but I checked the size of the index and dropped it and recreated it and the size went from 2.5GB to 1.3GB and my daily import into that table took almost half the time after recreating the primary key. I was wondering what the options are to reindex it. Should i not have a primary key and just a unique index so that I can concurrently reindex? Do I lose anything by replacing the primary key with a unique index? I prefer to have a primary key on the table for Slony, but I suppose I could make the OID column the primary key just for SLONY purposes. Any thoughts about the best approach would be appreciated. Note that this bloat on the primary key is from about 2-3 weeks of daily deletes/updates/inserts. I have multiple tables with similar structure and data size. Here are my autovac settings. I am on PostgreSQL 9.1.1 #autovacuum_max_workers = 3 # max number of autovacuum subprocesses #autovacuum_naptime = 1min # time between autovacuum runs autovacuum_vacuum_threshold = 20000 # min number of row updates before # vacuum default 50 autovacuum_analyze_threshold = 20000 # min number of row updates before # analyze default 50 autovacuum_vacuum_scale_factor = 0.1 # fraction of table size before vacuum autovacuum_analyze_scale_factor = 0.1 # fraction of table size before analyze #autovacuum_freeze_max_age = 200000000 # maximum XID age before forced vacuum autovacuum_vacuum_cost_delay = 5ms #autovacuum_vacuum_cost_limit = -1 Thanks RV -- View this message in context: http://postgresql.1045698.n5.nabble.com/Concurrent-Reindex-on-Primary-Key-for-large-table-tp5467243p5467243.html Sent from the PostgreSQL - sql mailing list archive at Nabble.com.
rverghese wrote on 08.02.2012 19:07: > I have a large table with about 60 million rows, everyday I add 3-4 million, > remove 3-4 million and update 1-2 million. I have a script that reindexes > concurrently a couple of times a week, since I see significant bloat. I have > autovac on and the settings are below. I can't concurrently reindex the > primary key, since there can be only one on a table. With 9.1 you can create a new index and drop and re-create the primary key using the new index. This still requires an exclusive lock on the table, but only for a very short moment: The following example is more or less taken from the manual: http://www.postgresql.org/docs/9.1/static/sql-altertable.html create unique concurrently new_index on your_table(your_pk); alter table your_table drop primary key; alter table your_table add primary key using index new_index; As this can be done in one transaction it should be safe with regards to the primary key. Thomas
Thanks! That worked. Any thoughts about containing index bloat. I thought the autovac would clean it up a bit more. Would any tweaks to my settings improve autovac performance? I am still doing a couple of concurrent reindexes per week otherwise performance degrades over a couple of days. Thanks RV -- View this message in context: http://postgresql.1045698.n5.nabble.com/Concurrent-Reindex-on-Primary-Key-for-large-table-tp5467243p5470216.html Sent from the PostgreSQL - sql mailing list archive at Nabble.com.
> -----Original Message----- > From: rverghese [mailto:riyav@hotmail.com] > Sent: Thursday, February 09, 2012 12:49 PM > To: pgsql-sql@postgresql.org > Subject: Re: Concurrent Reindex on Primary Key for large table > > Thanks! That worked. > > Any thoughts about containing index bloat. I thought the autovac would > clean it up a bit more. Would any tweaks to my settings improve autovac > performance? I am still doing a couple of concurrent reindexes per week > otherwise performance degrades over a couple of days. > > Thanks > RV > > -- > View this message in context: > http://postgresql.1045698.n5.nabble.com/Concurrent-Reindex-on-Primary- > Key-for-large-table-tp5467243p5470216.html > Sent from the PostgreSQL - sql mailing list archive at Nabble.com. Did you try to make autovacuum "more aggressive" like lowering autovacuum_vacuum_threshold from 20000? Regards, Igor Neyman
Hi I had another question, what about when the primary key is a foreign key in another table? Is the only option to drop the FK and recreate it after the primary key has been created with the new index? Thanks! RV -- View this message in context: http://postgresql.1045698.n5.nabble.com/Concurrent-Reindex-on-Primary-Key-for-large-table-tp5467243p5506261.html Sent from the PostgreSQL - sql mailing list archive at Nabble.com.