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Questions tagged [consistency]

In database systems, a consistent transaction is one that does not violate any integrity constraints during its execution. If a transaction leaves the database in an illegal state, it is aborted and an error is reported.

Consistency is one of the ACID properties that ensures that any changes to values in an instance are consistent with changes to other values in the same instance. A consistency constraint is a predicate on data which serves as a precondition, post-condition, and transformation condition on any transaction.

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C++ ensuring a float size of 4 bytes

I need a cross-architecture way to ensure that a float will be 4 bytes (as is on 32-bit windows). For instance, in the structs I'm creating, I'm using __int32 instead of int to ensure an integer value that is 4 bytes long. How could I do this with a…
Qix - MONICA WAS MISTREATED
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What is the difference between Sequential Consistency and Eventual Consistency?

There are two definitions I found on the Internet: Sequential consistency -- the result of any execution is the same as if the operations of all the processors were executed in some sequential order, and the operations of each individual processor…
Sergey
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Hazelcast: Questions regarding multi-node consistency

(I could not find a good source explaining this, so if it is available elsewhere, you could just point me to it) Hazelcast replicates data across all nodes in clusters. So, if data is changed in one of the nodes, does the node update its own copy…
gammay
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Is it possible to run a Neo4j cluster with strong consistency?

The docs of Neo4j state that when running in HA mode, you get eventual consistency. This is a quote from that page: All updates will however propagate from the master to other slaves eventually so a write from one slave may not be immediately…
falconizer
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How can MySQL Cluster 7.3 achieve 99,999% Availability? Antithesis to CAP Theorem

According to the "Guide to Scaling Web Databases with MySQL Cluster", MySQL Cluster 7.3 can acchieve 99,999% availability while using synchronous update replication. This would be a antithesis to the CAP Theorem since it states that perfect…
NorRen
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Combining Neo4J and MongoDB : Consistency

I am experimenting a lot these days, and one of the things I wanted to do is combine two popular NoSQL databases, namely Neo4j and MongoDB. Simply because I feel they complement eachother perfectly. The first class citizens in Neo4j, the relations,…
Pieter-Jan
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Google Cloud Storage not strongly consistent, returning 404 until 500ms after a resumable upload completes

I am making a file uploader using Cloud Storage which is experiencing non-consistent behaviour which seems contrary to the documentation. When you upload an object to Cloud Storage, and you receive a success response, the object is immediately…
scipilot
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Can pseudo "lock" objects be used in the Amazon S3 API?

I'm thinking about using "lock" S3 objects in order to prevent simultaneous identical operations on a given S3 object. But I have great doubts about the validity of this technical solution. More precisely, at the beginning of an operation on an…
Azzip
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Choosing a NoSQL database for storing events in a CQRS designed application

I am looking for a good, up to date and "decision helping" explanation on how to choose a NoSQL database engine for storing all the events in a CQRS designed application. I am currently a newcomer to all things around NoSQL (but learning): please be…
Yonn Trimoreau
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"Official" docker backup strategy - what about consistency?

The suggested strategy to manage and backup data in docker looks something like this: docker run --name mysqldata -v /var/lib/mysql busybox true docker run --name mysql --volumes-from mysqldata mysql docker run --volumes-from mysqldata -v…
S1lentSt0rm
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Controling eventual AppEngine datastory consistency during testing

I have an AppEngine app written in Go, and I'm trying to improve my tests. Part of the tests that I need to run are a series of create, update, delete queries on the same object. However given that the datastore is eventually consistent (these…
JohnGB
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One table DAO vs multiple table DAO

I am designing some "blocks" of data in JSF and I am getting my data from a Java bean per block. My problem is that my blocks get their data from more than one table. For example: A block that describes personal data of a customer consists…
Stefanos Kargas
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Transaction with Cassandra data model

According to the CAP theory, Cassandra can only have eventually consistency. To make things worse, if we have multiple reads and writes during one request without proper handling, we may even lose the logical consistency. In other words, if we do…
aXqd
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Are dynamodb update expressions strongly consistent?

Suppose that a given table already contains the following key value pair: { "id": "one", "num": 5000 } If I write an update expression such as "ADD num :val" to add values as necessary can I expect this to be consistent in case of parallel…
codejammer
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What exactly is the difference between REQUEST_PLUS and STATEMENT_PLUS ScanConsistency in Couchbase?

I couldn't understand the different between a request and a statement and how consistency is related to each of them.
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