Analysis of Handling Processes of Record Versions in NoSQL Databases

This article investigates the handling processes versions of a record in NoSQL databases. The goal of this work is to develop a model, which enables users both to handle record versions and work with a record simultaneously. This model allows us to estimate both a time distribution for users to handle record versions and a distribution of the count of record versions. With eventual consistency (W=R=1) there is a possibility for several users to update any record simultaneously. In this case, several versions of records with the same key will be stored in database. When reading, the user obtains all versions, handles them, and saves a new version, while older versions are deleted. According to the model, the user’s time for handling the record versions consists of two parts: random handling time of each version and random deliberation time for handling a result. Record saving time and records deleting time are much less than handling time, so, they are ignored in the model. The paper offers two model variants. According to the first variant, client's handling time of one record version is calculated as the sum of random handling times of one version based on the count of record versions. This variant ignores explicitly the fact that handling time of record versions may depend on the update count, performed by the other users between the sequential updates of the record by the current client. So there is the second variant, which takes this feature into consideration. The developed models were implemented in the GPSS environment. The model experiments with different counts of clients and different ratio between one record handling time and results deliberation time were conducted. The analysis showed that despite the resemblance of model variants, a difference in change nature between average values of record versions count and handling time is significant. In the second variant dependences of the average count of record versions in database and its right bound of the confidence interval on the average deliberation time have a pronounced maximum. In the same variant an average handling time of record versions practically does not depend on the average deliberation time, but the right bound of the confidence interval of this time has a pronounced minimum