Analyzing and understanding the characteristics of the incoming workload is crucial in unraveling trends and tuning the performance of a database system. In this work, we present Oracle Workload Intelligence (WI), a tool for workload modeling and mining, as our attempt to infer the processes that generate a given workload. WI consists of two main functionalities. First, WI derives a model that captures the main characteristics of the workload without overfitting, which makes it likely to generalize well to unseen instances of the workload. Such a model provides insights into the most frequent code paths in the application that drives the workload, and also enables optimizations inside the database system that target sequences of query statements. Second, WI can compare the models of different snapshots of the workload to detect whether the workload has changed. Such changes might indicate new trends, regressions, problems, or even security issues. We demonstrate the effectiveness of WI with an experimental study on synthetic workloads and customer-provided application benchmarks.

Given a replicated database, a divergent design tunes the indexes in each replica differently in order to specialize it for a specific subset of the workload. Empirical studies have shown that this specialization brings significant performance gains compared to the common practice of having the same indexes in all replicas. However, reaping the benefits of divergent designs requires the development of new tuning tools for database administrators, and the existing tools unfortunately suffer from severe shortcomings: they assume a fixed number of replicas and a known workload distribution, and ignore the possibility of replica failures and the subsequent effect on load imbalance.

Healthcare systems around the world are facing the challenge of information overload in caring for patients in an affordable, safe and high-quality manner in a system with limited healthcare resources and increasing costs. To alleviate this problem, we develop an integrative healthcare analytics system called GEMINI which allows point of care analytics for doctors where real-time usable and relevant information of their patients are required through the questions they asked about the patients they are caring for. GEMINI extracts data of each patient from various data sources and stores them as information in a patient profile graph. The data sources are complex and varied consisting of both structured data (such as, patients' demographic data, laboratory results and medications) and unstructured data (such as, doctors' notes). Hence, the patient profile graph provides a holistic and comprehensive information of patients' healthcare profile, from which GEMINI can infer implicit information useful for administrative and clinical purposes, and extract relevant information for performing predictive analytics. At the core, GEMINI keeps interacting with the healthcare professionals as part of a feedback loop to gather, infer, ascertain and enhance the self-learning knowledge base. We present a case study on using GEMINI to predict the risk of unplanned patient readmissions.

Sorting is a fundamental operation in data processing. While the problem of sorting flat data records has been extensively studied, there is very little work on sorting hierarchical data such as XML documents. Existing hierarchy-aware sorting approaches for hierarchical data are based on creating sorted subtrees as initial sorted runs and merging sorted subtrees to create the sorted output using either explicit pointers or absolute node key comparisons for merging subtrees. In this paper, we propose SliceSort, a novel, level-wise sorting technique for hierarchical data that avoids the drawbacks of subtree-based sorting techniques. Our experimental performance evaluation shows that SliceSort outperforms the state-of-art approach, HErMeS, by up to a factor of 27%.

Index tuning; i.e., selecting indexes that are appropriate for the workload to obtain good system performance, is a crucial task for database administrators. Administrators rely on automated index advisors for this task, but existing advisors work either offline, requiring a-priori knowledge of the workload, or online, taking the administrator out of the picture and assuming total control of the index tuning task. Semi-automatic index tuning is a new paradigm that achieves a middle ground: the advisor analyzes the workload online and provides recommendations tailored to the current workload, and the administrator is able to provide feedback to refine future recommendations. In this demonstration we present Kaizen, an index tuning tool that implements semi-automatic tuning.

Many applications often require finding a set of items of interest with respect to some aggregation constraints. For example, a tourist might want to find a set of places of interest to visit in a city such that the total expected duration is no more than six hours and the total cost is minimized. We refer to such queries as SAC queries for ``set-based with aggregation constraints'' queries. The usefulness of SAC queries is evidenced by the many variations of SAC queries that have been studied which differ in the number and types of constraints supported. In this paper, we make two contributions to SAC query evaluation. We first establish the hardness of evaluating SAC queries with multiple count constraints and presented a novel, pseudo-polynomial time algorithm for evaluating a non-trivial fragment of SAC queries with multiple sum constraints and at most one of either count, group-by, or content constraint. We also propose a heuristic approach for evaluating general SAC queries. The effectiveness of our proposed solutions is demonstrated by an experimental performance study.

One useful feature that is missing from today's database systems is an explain capability that enables users to seek clarifications on unexpected query results. There are two types of unexpected query results that are of interest: the presence of unexpected tuples, and the absence of expected tuples (i.e., missing tuples). Clearly, it would be very helpful to users if they could pose follow-up why and why-not questions to seek clarifications on, respectively, unexpected and expected (but missing) tuples in query results. While the why questions can be addressed by applying established data provenance techniques, the problem of explaining the why-not questions has received very little attention. There are currently two explanation models proposed for why-not questions. The first model explains a missing tuple t in terms of modifications to the database such that t appears in the query result wrt the modified database. The second model explains by identifying the data manipulation operator in the query evaluation plan that is responsible for excluding t from the result. In this paper, we propose a new paradigm for explaining a why-not question that is based on automatically generating a refined query whose result includes both the original query's result as well as the user-specified missing tuple(s). In contrast to the existing explanation models, our approach goes beyond merely identifying the "culprit" query operator responsible for the missing tuple(s) and is useful for applications where it is not appropriate to modify the database to obtain missing tuples.

It has recently been asserted that the usability of a database is as important as its capability. Understanding the database schema, the hidden relationships among attributes in the data all play an important role in this context. Subscribing to this viewpoint, in this paper, we present a novel data-driven approach, called Query By Output (QBO), which can enhance the usability of database systems. The central goal of QBO is as follows: given the output of some query Q on a database D, denoted by Q(D), we wish to construct an alternative query Q′ such that Q(D) and Q′ (D) are instance-equivalent. To generate instance-equivalent queries from Q(D), we devise a novel data classification-based technique that can handle the at-least-one semantics that is inherent in the query derivation. In addition to the basic framework, we design several optimization techniques to reduce processing overhead and introduce a set of criteria to rank order output queries by various notions of utility. Our framework is evaluated comprehensively on three real data sets and the results show that the instance-equivalent queries we obtain are interesting and that the approach is scalable and robust to queries of different selectivities.