Abstract
This research shows a protocol to assess the computational complexity of querying relational and non-relational (NoSQL (not only Structured Query Language)) standardized electronic health record (EHR) medical information database systems (DBMS). It uses a set of three doubling-sized databases, i.e. databases storing 5000, 10,000 and 20,000 realistic standardized EHR extracts, in three different database management systems (DBMS): relational MySQL object-relational mapping (ORM), document-based NoSQL MongoDB, and native extensible markup language (XML) NoSQL eXist.The average response times to six complexity-increasing queries were computed, and the results showed a linear behavior in the NoSQL cases. In the NoSQL field, MongoDB presents a much flatter linear slope than eXist.NoSQL systems may also be more appropriate to maintain standardized medical information systems due to the special nature of the updating policies of medical information, which should not affect the consistency and efficiency of the data stored in NoSQL databases.One limitation of this protocol is the lack of direct results of improved relational systems such as archetype relational mapping (ARM) with the same data. However, the interpolation of doubling-size database results to those presented in the literature and other published results suggests that NoSQL systems might be more appropriate in many specific scenarios and problems to be solved. For example, NoSQL may be appropriate for document-based tasks such as EHR extracts used in clinical practice, or edition and visualization, or situations where the aim is not only to query medical information, but also to restore the EHR in exactly its original form.
Highlights
NoSQL ( SQL) database systems (DBMS) have recently emerged as an alternative to traditional Relational DBMS (RDMBS)
The average response times to six complexity-increasing queries were computed, and the results showed a linear behavior in the NoSQL cases
This protocol shows that pure relational object-relational mapping (ORM) systems do not seem practical for single-patient queries (Q1, Q3, and Q4) since response times are slower, probably due to a high number of relational tables performing many expensive join operations, and due to the storage system used by the specific kind of database
Summary
NoSQL ( SQL) DBMS have recently emerged as an alternative to traditional Relational DBMS (RDMBS). RDBMS have dominated the way data were stored in database systems for decades. Well-studied and understood relational algebra and calculus have guaranteed the efficiency and consistency of RDBMS1. NoSQL systems will not become substitutes for relational systems, but they could behave advantageously in certain scenarios and under several conditions. Some of these particular scenarios and conditions would occur when designing the database persistence of Electronic Health Record (EHR) systems used to manage and store medical information. In order to be interoperable and sustainable in practice, several international standards such as ISO/EN 13606, openEHR, and HL72,3,4,5 have been used to standardize EHR extracts
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