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Re: [Postgres-xc-general] Do you think the new feature is meaningful? - Read/Write Separation
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From: 鈴木 幸市 <ko...@in...> - 2014-06-05 05:20:09
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More robust node redundancy and read-only slave will be one of the next issue. Hope to have much more input on this. I’m going to open next roadmap discussion. --- Koichi Suzuki 2014/06/03 3:33、Mason Sharp <ms...@tr...<mailto:ms...@tr...>> のメール： On Sun, May 25, 2014 at 2:04 PM, Koichi Suzuki <koi...@gm...<mailto:koi...@gm...>> wrote: I see. Your have good usecase for read-only transactions. Because of the nature of log shipping and sharing/clustering, it is not simple to provide read-only transaction in XC. There may be cases where it is being used as a data warehouse (thinking a bit more about Postgres-XL here), where there is a nightly load process and then reads are done during the day. If the standbys are dedicated, being able to load balance them could be useful. Two essential reasons: 1. Delay in WAL playback in each slave may be different. It makes providing consistent database view extremely difficult. 2. At present, slave calculates snapshot of the transaction from the WAL. Current code does not allow missing XIDs. There will be memory leak and crash by OOM if there's many missing XIDs in the WAL stream. In XC, it is disabled and the database view may be inconsistent. Please note that this does not affect recovery and promotion. Agreed, there may be some level of effort for this. -- Mason Sharp TransLattice - http://www.translattice.com<http://www.translattice.com/> Distributed and Clustered Database Solutions ------------------------------------------------------------------------------ Learn Graph Databases - Download FREE O'Reilly Book "Graph Databases" is the definitive new guide to graph databases and their applications. Written by three acclaimed leaders in the field, this first edition is now available. Download your free book today! http://p.sf.net/sfu/NeoTech_______________________________________________ Postgres-xc-general mailing list Pos...@li... https://lists.sourceforge.net/lists/listinfo/postgres-xc-general |
