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Which modern databases support ACID transactions?
- zshprompt 13y agoWhere is Datomic?
- hcarvalhoalves 13y agoFrom what I understand, Datomic sidesteps the ACID issue altogether by dealing with immutable data at the application layer. You add your changes on top of a version of the database, so you're always working on a consistent view of the database (pretty much like Git). On the backend, Datomic doesn't implement it's own storage, it plugs into SQL databases, Riak, etc. so you may or may not have ACID at that level.
- bmm6o 13y agoAnd MSSQL?
- oconnor663 13y agoPresumably SQL Server fits somewhere up at the top with MySQL/Postgres/Oracle?
- nlavezzo 13y agoYep.
- voidmain 13y agoAs far as we know, Datomic's (noninteractive) transactions are ACID. You would do better to ask them, though. The list isn't intended to be exhaustive!
- VaedaStrike 13y agoThe absence of Datomic seems a tad suspect.
- MichaelGG 13y agoVoltDB uses a partitioned data model. For OLTP apps that fit within that model, it's incredibly fast and there's no global transaction. For transactions that span partitions, yes, there is a lock. If your app fits the model (and a lot of transaction processing does), then it's quite amazing. For instance, one model I've played with is updating customer balances in realtime. If I partition everything on CustomerId, then I can insert new charges and update balances at extremely high rates (over 50Ktps per node, at least). If your app requires (edit: a significant amount of) transactions that have no locality, that is multiple arbitrary rows might be updated in any transaction, VoltDB might not be for you. If I understand Spanner, it, too, has a somewhat-partitioned model, with parent/child relationships, correct?
- voidmain 13y agoSpanner can do partition-spanning transactions with a useful throughput.
- jhugg 13y agoTwo things to point out as a VoltDB engineer. 1) VoltDB's global transactions are much slower than its partitioned transactions, but it's relative. It can still do hundreds or thousands per second. 2) Making this number faster for common cases is ongoing work. In upcoming 4.0, multi-partition consistent reads will get about a 10x performance boost if they're bottlenecked on transaction overhead. This allows us to do up to 50k/sec global reads while doing 500k/sec partitioned writes. Expect improvements for global writes in 2014.
- lcampbell 13y ago> MySQL provides ACID transactions on a single machine That made me chortle. If you can't roll back an `ALTER TABLE` command (e.g., to back out of a failed schema migration), you don't really have good ACID semantics. Here's a list of other fun MySQL commands that sidestep transactions: http://dev.mysql.com/doc/refman/5.5/en/implicit-commit.html http://dev.mysql.com/doc/refman/5.5/en/implicit-commit.html
- gizmogwai 13y agoACID refers to actions that can take place within a transaction. Transactions refer to logical operation to the data. The data is the content, not de container. DML affects content, DDL affects the container. ALTER TABLE is a DDL operation. Now, I know that _some_ databases offer some level of support to include DLL operations within a transaction, but its far from being common, and most of the implementations are quite recent.
- mathnode 13y agoTransactional DDL is a dangerous game with any DBMS. You must know the idioms of the systems you use, and use them accordingly. You would be a fool otherwise.
- Dylan16807 13y agoIsn't ALTER TABLE a fundamentally slow and blocking action anyway? It's easy enough to make a new table and swap it in. Transactions for row-level actions are far more important.
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- daigoba66 13y ago> RavenDB uses a weak form of isolation called "snapshot isolation". ... Index updates are not Atomic. If MVCC (http://en.wikipedia.org/wiki/Multiversion_concurrency_control http://en.wikipedia.org/wiki/Multiversion_concurrency_contro...) is "weak", then are they claiming read/write locks are better? Also, to nitpick, RavenDB's reads/writes in the document storage engine are entirely atomic. A lucene index is maintained in a secondary store which is eventually consistent. But as a document store supports ACID transactions.
- voidmain 13y agoAs we disclaim on the page itself, we aren't experts on all of these databases, so it's possible that we've made a mistake. We are relying on the documentation of other products (but on the specific documented claims rather than whether they throw around the term "ACID"). 'Snapshot isolation' is a level of isolation guarantee, not an implementation technique. It means that a transaction will read values consistently at one point in history and then write values at a later point, even though the read values may change in between. To give a classic example, pure snapshot isolation doesn't allow you to soundly transfer $100 from Alice's account to Bob's account. FoundationDB uses MVCC and optimistic concurrency, but provides serializable isolation. Besides this, and the asynchronous indexing that you mention, RavenDB uses an "XA" type technique for cross-node transactions which relies on the durability of an external transaction coordinator. Various public statements of the developers lead me to think that they don't find this arrangement more trustworthy than I do. "Local" transactions on a single document don't qualify as ACID transactions; that's one of the primary messages of the page you are linking to.
- brettinlj 13y agoIt would be nice to see a "NewSQL" database like Clustrix in this comparison. From my understanding of their white papers the transactions are ACID.
- voidmain 13y agoWe have been told by people who should know that Clustrix does not provide serializable transactions, but since this claim is unspecific and not based on publically available information we haven't put it on the page.
- brettinlj 13y agoApparently as per their docs (http://docs.clustrix.com/plugins/viewsource/viewpagesrc.action?pageId=1769594 http://docs.clustrix.com/plugins/viewsource/viewpagesrc.acti...) this is true specific to end-user transactions: "Note: serializable isolation not currently available to end user transactions." The Serializeable isolation level is used for data moves within the cluster according to the table referencing isolation levels and row visibility rules.
- hardwaresofton 13y agoWhat about RethinkDB?
- utopkara 13y agoFrom RethinkDB FAQ (http://www.rethinkdb.com/faq/ http://www.rethinkdb.com/faq/) "RethinkDB is not a good choice if you need full ACID support or strong schema enforcement — in this case you are better off using a relational database such as MySQL or PostgreSQL."
- lafar6502 13y agoheh, this applies to all 'new' databases - if you aren't sure which one to choose, you're usually better off staying with a relational. You'll be bleeding edge in few years when SQL is forgotten and then re-discovered.
- hardwaresofton 13y agoYes, but I was more thinking where was the mention -- while it's not particularly good for ACID properties I like rethinkdb, as a nosql DB
- lafar6502 13y agoI'm afraid there were more 'databases' created in last 2 years than in all earlier history of human civilization. This suggests authors of some of these products have yet to discover what ACID means and how many problems they didn't even think of have already been solved many years ago.
- lsh123 13y agoWe use MySQL-Galera and it has full ACID guarantees in cluster/multi-site/DR environment. Unfortunately the article is not a complete overview of the existing DBs landscape and has too much marketing in other places as well.
- voidmain 13y agoI know very little about Galera replication, but its FAQ states that it provides only snapshot isolation. You are certainly correct that we have not provided a complete overview of the DB market! That is a very ambitious project. We built this page largely to call out the use of "ACID" terminology by vendors that don't actually provide it.
- lsh123 13y agoI personally think that "provides only snapshot isolation" and "provides ACID transactions on a single machine, but sharding, caching, and failover will likely violate them as you try to scale" are very different statements. The different isolation modes does not violate ACID transactions and only describe the semantic in more details. I would make a claim that majority of applications can use any isolation mode with ACID transactions as long as application developers understand what exactly going on.
- voidmain 13y agoIsolation levels describe the degree of compliance with the I in ACID. Full compliance is called serializable isolation. Are there valuable uses for lower degrees of isolation? Yes, and a good database should allow applications to selectively reduce isolation. But the inability to support serializable isolation greatly limits the power and composability of a system. Galera looks like an extremely useful tool, and a big improvement on usual (and extremely dangerous) ad hoc failover. Besides the limited isolation level, though, it only really solves failover. Typical large scale database deployments will sacrifice even more ACID properties by sharding (which loses A, C, and I for shard-spanning transactions) and frequently by incoherent caching (which sacrifices isolation for reads that use the cache).
- hugofirth 13y agoAm I wrong in thinking that [Neo4j](http://www.neo4j.org/ http://www.neo4j.org/) supports fully ACID compliant transactions?
- gizmogwai 13y agoBy default, Neo4J is not ACID compliant as it works mainly in memory, which fails the Durability part of ACID. I am not event sure that if you would configure it to be in sync with its stored replica, it would pass ACID test due to how Java handle the files internally.
- hugofirth 13y agoFair enough - my experience with Neo is at this point shallow at best. I had seen it in the feature spec is all. Should they be claiming they are if they aren't however?
- bradwestness 13y agoMaking no mention of Microsoft SQL Server seems like a pretty big oversight.
- rblatz 13y agoDidn't you get the memo? By modern they meant not MS.
- bunderbunder 13y agoAll the more peculiar, then, that they list RavenDB.
- ape4 13y agoI'd never use Microsoft SQL Server since it doesn't run my preferred OS: Linux.
- rpedela 13y agoI thought PostgreSQL's replication was ACID-compliant?
- zafirk 13y agoGoogle Cloud Datastore - https://developers.google.com/datastore/ https://developers.google.com/datastore/ and Google Cloud SQL https://developers.google.com/cloud-sql/faq https://developers.google.com/cloud-sql/faq
- SCdF 13y agoWorth mentioning (if it's not obvious) that this is written by the FoundationDb guys, on their site, and so will clearly show a bias toward their product (surprise!, it does!). There is still some interesting information here, but there are some notable missing players here (MSSQL) who I presume are missing because not including them paints Foundation in a better light.
- webmaven 13y agoFirebird should be added to the ACID compliant list as well: http://www.firebirdsql.org/file/documentation/papers_presentations/html/paper-fbent-acid.html http://www.firebirdsql.org/file/documentation/papers_present...
- lvca 13y agoOrientDB (www.orientdb.org) Graph Database supports ACID transactions since the first version. It has SQL, Document Database features and it's distributed. Did FoundationDB inspire to OrientDB?