> Arguably, the other alternative to server-side denormalization is to do the denormalization client-side which comes with the same axes of costs and complexity, just with more of each.
That's not completely true. You can write to any number of tables without doing a read, and the cost of reading data off disk is significantly greater than an insert alone. You can crush a cluster with a write heavy workload and MVs that would otherwise be completely fine to do all writes. The other issue with MVs is that you still need to understand fundamentals of data modeling, that don't magically solve the problem of enormous partitions. One of the reasons I've had to un-MV a lot of clusters is because people have put an MV on a table with a low-cardinality field and found themselves with a 10GB partition nightmare, so they need to go back and remodel the view as something more complex anyways. In this case, the MV was extremely high cost since now they've not only pushed out a poor implementation to begin with but now have the cost of a migration as well as a rewrite. On Wed, Aug 28, 2019 at 9:58 AM Joshua McKenzie <jmcken...@apache.org> wrote: > > > > so we need to start migration from MVs to manual query base table ? > > Arguably, the other alternative to server-side denormalization is to do > the denormalization client-side which comes with the same axes of costs and > complexity, just with more of each. > > Jeff's spot on when he discusses the risk appetite vs. mitigation aspect of > it. There's a reason banks do end-of-day close-out validation analysis and > have redundant systems for things like this. > > On Wed, Aug 28, 2019 at 11:49 AM Jon Haddad <j...@jonhaddad.com> wrote: > > > I've helped a lot of teams (a dozen to two dozen maybe) migrate away from > > MVs due to inconsistencies, issues with streaming (have you added or > > removed nodes yet?), and massive performance issues to the point of > cluster > > failure under (what I consider) trivial load. I haven't gone too deep > into > > analyzing their issues, folks are usually fine with "move off them", vs > > having me do a ton of analysis. > > > > tlp-stress has a materialized view workload built in, and you can add > > arbitrary CQL via the --cql flag to add a MV to any existing workload > such > > as KeyValue or BasicTimeSeries. > > > > On Wed, Aug 28, 2019 at 8:11 AM Jeff Jirsa <jji...@gmail.com> wrote: > > > > > There have been people who have had operational issues related to MVs > > (many > > > of them around running repair), but the biggest concern is correctness. > > > > > > It probably ultimately depends on what type of database you're running. > > If > > > you're running some sort of IOT / analytics workload and you just want > > > another way to SELECT the data, but you won't notice one of a billion > > > records going missing, using MVs may be fine. If you're a bank, and one > > of > > > a billion records going missing means you lose someone's bank account, > I > > > would avoid using MVs. > > > > > > It's all just risk management. > > > > > > On Wed, Aug 28, 2019 at 7:18 AM Pankaj Gajjar < > > > pankaj.gaj...@contentserv.com> > > > wrote: > > > > > > > Hi Michael, > > > > > > > > Thanks for putting very clever information " Users of MVs *must* > > > determine > > > > for themselves, through > > > > thorough testing and understanding, if they wish to use them." > And > > > > this concluded that if there is any issue occur in future then only > > > > solution is to rebuild the MVs since Cassandra does not able to make > > > > consistent synch well. > > > > > > > > Also, we practically using the 10+ MVs and as of now, we have not > faced > > > > any issue, so my question to all community member, does anyone face > any > > > > critical issues ? so we need to start migration from MVs to manual > > query > > > > base table ? > > > > > > > > Also, I can understand now, it's experimental and not ready for > > > > production, so if possible, please ignore it only right ? > > > > > > > > Thanks > > > > Pankaj > > > > > > > > On 27/08/19, 19:03, "Michael Shuler" <mshu...@pbandjelly.org on > > behalf > > > > of mich...@pbandjelly.org> wrote: > > > > > > > > It appears that you found the first message of the chain. I > suggest > > > > reading the linked JIRA and the complete dev@ thread that > arrived > > at > > > > this conclusion; there are loads of well formed opinions and > > > > information. Users of MVs *must* determine for themselves, > through > > > > thorough testing and understanding, if they wish to use them. > > > > > > > > Linkage: > > > > https://issues.apache.org/jira/browse/CASSANDRA-13959 > > > > (sub-linkage..) > > > > https://issues.apache.org/jira/browse/CASSANDRA-13595 > > > > https://issues.apache.org/jira/browse/CASSANDRA-13911 > > > > https://issues.apache.org/jira/browse/CASSANDRA-13880 > > > > https://issues.apache.org/jira/browse/CASSANDRA-12872 > > > > https://issues.apache.org/jira/browse/CASSANDRA-13747 > > > > > > > > Very much worth reading the complete thread: > > > > part1: > > > > > > > > > > > > > > https://lists.apache.org/thread.html/d81a61da48e1b872d7599df4edfa8e244d34cbd591a18539f724796f@ > > > > <dev.cassandra.apache.org> > > > > part2: > > > > > > > > > > > > > > https://lists.apache.org/thread.html/19b7fcfd3b47f1526d6e993b3bb97f6c43e5ce204bc976ec0701cdd3@ > > > > <dev.cassandra.apache.org> > > > > > > > > Quick JQL for open tickets with "mv": > > > > > > > > > > > > > > https://issues.apache.org/jira/issues/?jql=project%20%3D%20CASSANDRA%20AND%20text%20~%20mv%20AND%20status%20!%3D%20Resolved > > > > > > > > -- > > > > Michael > > > > > > > > On 8/27/19 5:01 AM, pankaj gajjar wrote: > > > > > Hello, > > > > > > > > > > > > > > > > > > > > concern about Materialized Views (MVs) in Cassandra. > > Unfortunately > > > > starting > > > > > with version 3.11, MVs are officially considered experimental > and > > > > not ready > > > > > for production use, as you can read here: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > http://mail-archives.apache.org/mod_mbox/cassandra-user/201710.mbox/%3cetpan.59f24f38.438f4e99.7...@apple.com%3E > > > > > > > > > > > > > > > > > > > > Can you please someone give some productive feedback on this ? > it > > > > would > > > > > help us to further implementation around the MVs in Cassandra. > > > > > > > > > > > > > > > > > > > > Does anyone facing some critical issue or data lose or > > > > synchronization > > > > > issue ? > > > > > > > > > > > > > > > > > > > > Regards > > > > > > > > > > Pankaj. > > > > > > > > > > > > > > > --------------------------------------------------------------------- > > > > To unsubscribe, e-mail: dev-unsubscr...@cassandra.apache.org > > > > For additional commands, e-mail: dev-h...@cassandra.apache.org > > > > > > > > > > > > > > > > > > > > > >
