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Re: [Postgres-xc-general] Uncommited transaction? Weird issues with DDL and missing database
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From: Koichi S. <koi...@gm...> - 2015-07-10 06:03:49
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Yes, I agree. I began to write a code for this. In creating/dropping nodes, transaction level lock is used. Because some DDL don’t run inside the session block, I think we should use session level, although we need some error handling when the transaction aborts. Thank you; --- Koichi Suzuki https://www.linkedin.com/in/koichidbms 2015-07-10 14:11 GMT+09:00 Ashutosh Bapat <ash...@en...>: > I vaguely remember, Abbas had used advisory lock machinary for creating > and dropping nodes. May be we have to use the same mechanism for all DDLs. > > On Fri, Jul 10, 2015 at 9:43 AM, Koichi Suzuki <koi...@gm...> > wrote: > >> In PGXC, DDL operation is not serialized, I mean, the order of the node >> where each peace of DDL executed is not defined. This may cause some race >> conditions and could cause local errors, resulting in inconsistent status. >> >> Recetly, I found CREATE TABLE in parallel schedule of regression test >> cause similar problems. I think this is common to XC and XL. >> >> There are a couple of ways to fix this: >> >> 1. Use coordinator primary node to go first, as done in replicated tables, >> 2. Serialize DDL execution, possibly by using advisory lock internally. >> >> Anyway, this is a bug and we need a fix. Solution 1 is bit more >> complicated than 2. >> >> Best; >> >> --- >> Koichi Suzuki >> https://www.linkedin.com/in/koichidbms >> >> >> 2015-07-09 23:22 GMT+09:00 Artur Graniszewski <aa...@bo...>: >> >>> Hi, >>> >>> I just finished the multi-master configuration of Postgres XC on my test >>> environment (three virtual machines): >>> >>> * VM1 - with GTM only >>> * VM2, VM2 - two masters with one data-node and one coordinator on each >>> machine >>> >>> I tried to create some databases on each master to check if everything >>> works ok, but I found a strange issue with one database that had been >>> created only on one of the masters (while other databases I created and >>> deleted afterwards were ok): >>> >>> postgres=# \l >>> List of databases >>> Name | Owner | Encoding | Collate | Ctype | Access >>> privileges >>> >>> -----------+----------+----------+-------------+-------------+----------------------- >>> postgres | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 | >>> template0 | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 | >>> =c/postgres + >>> | | | | | >>> postgres=CTc/postgres >>> template1 | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 | >>> =c/postgres + >>> | | | | | >>> postgres=CTc/postgres >>> test2 | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 | >>> whatnot | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 | >>> >>> vs >>> >>> postgres=# \l >>> List of databases >>> Name | Owner | Encoding | Collate | Ctype | Access >>> privileges >>> >>> -----------+----------+----------+-------------+-------------+----------------------- >>> postgres | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 | >>> template0 | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 | >>> =c/postgres + >>> | | | | | >>> postgres=CTc/postgres >>> template1 | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 | >>> =c/postgres + >>> | | | | | >>> postgres=CTc/postgres >>> whatnot | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 | >>> >>> Unfortunately, when I try to perform any DDL command on a server that >>> sees "test2" database I receive the following errors: >>> >>> postgres=# drop database test2; >>> ERROR: database "test2" does not exist >>> postgres=# create database test2; >>> ERROR: database "test2" already exists >>> >>> Also, when I try to remove another database called "whatnot", drop >>> operation never finishes. It looks like a transaction that hangs some DDL >>> operations: >>> >>> postgres=# select * from pgxc_prepared_xacts; >>> pgxc_prepared_xact >>> -------------------- >>> T74589 >>> (1 row) >>> >>> postgres=# select * from pg_prepared_xacts; >>> transaction | gid | prepared | owner | >>> database >>> >>> -------------+--------+-------------------------------+----------+---------- >>> 73716 | T73716 | 2015-07-09 12:58:25.823385+02 | postgres | >>> postgres >>> (1 row) >>> >>> postgres=# >>> >>> When I try to rollback the transaction, Postgres says that given GID >>> does not exist. >>> >>> Is it a bug in Postgres XC? Is there a way to synchronize the masters? >>> (eg delete "test2" on one master and "whatnot" on both of them). Please >>> keep in mind that I created/dropped more databases without any issues, so >>> I'm unsure what went wrong in case of these two specific databases. >>> >>> Cheers, >>> >>> Artur >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> ------------------------------------------------------------------------------ >>> Don't Limit Your Business. Reach for the Cloud. >>> GigeNET's Cloud Solutions provide you with the tools and support that >>> you need to offload your IT needs and focus on growing your business. >>> Configured For All Businesses. Start Your Cloud Today. >>> https://www.gigenetcloud.com/ >>> _______________________________________________ >>> Postgres-xc-general mailing list >>> Pos...@li... >>> https://lists.sourceforge.net/lists/listinfo/postgres-xc-general >>> >>> >> >> >> ------------------------------------------------------------------------------ >> Don't Limit Your Business. Reach for the Cloud. >> GigeNET's Cloud Solutions provide you with the tools and support that >> you need to offload your IT needs and focus on growing your business. >> Configured For All Businesses. Start Your Cloud Today. >> https://www.gigenetcloud.com/ >> _______________________________________________ >> Postgres-xc-general mailing list >> Pos...@li... >> https://lists.sourceforge.net/lists/listinfo/postgres-xc-general >> >> > > > -- > Best Wishes, > Ashutosh Bapat > EnterpriseDB Corporation > The Postgres Database Company > |
