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When running OLTP workloads, relational DBMSs with flash SSDs still suffer from the durability overhead. Heavy writes to SSD not only limit the performance but also shorten the storage lifespan. To mitigate the durability overhead, this paper proposes a new database architecture, NV-SQL. NV-SQL aims at absorbing a large fraction of writes written from DRAM to SSD by introducing NVDIMM into the memory hierarchy as a durable write cache. On the new architecture, NV-SQL makes two technical contributions. First, it proposes the re-update interval-based admission policy that determines which write-hot pages qualify for being cached in NVDIMM. It is novel in that the page hotness is based solely on pages' LSN. Second, this study finds that NVDIMM-resident pages can violate the page action consistency upon crash and proposes how to detect inconsistent pages using per-page in-update flag and how to rectify them using the redo log. NV-SQL demonstrates how the ARIES-like logging and recovery techniques can be elegantly extended to support the caching and recovery for NVDIMM data. Additionally, by placing write-intensive redo buffer and DWB in NVDIMM, NV-SQL eliminates the log-force-at-commit and WAL protocols and further halves the writes to the storage. Our NV-SQL prototype running with a real NVDIMM device outperforms the same-priced vanilla MySQL with larger DRAM by several folds in terms of transaction throughput for write-intensive OLTP benchmarks. This confirms that NV-SQL is a cost-performance efficient solution to the durability problem.

High-speed data ingestion is critical in time-series workloads that are driven by the growth of Internet of Things (IoT) applications. We observe that traditional tree-based indexes encounter severe scalability bottlenecks for time-series workloads that insert monotonically increasing timestamp keys into an index; all insertions go to a small memory region that sees extremely high contention. In this work, we present a new index design, B link -hash, that enhances a tree-based index with hash leaf nodes to mitigate the contention of monotonic insertions --- insertions go to random locations within a hash node (which is much larger than a B+-tree node) to reduce conflicts. We develop further optimizations (median approximation and lazy split) to accelerate hash node splits. We also develop structure adaptation optimizations to dynamically convert a hash node to B+-tree nodes for good scan performance. Our evaluation shows that B link -hash achieves up to 91.3× higher throughput than conventional indexes in a time-series workload that monotonically inserts timestamps into an index, while showing comparable scan performance to a well-optimized B+-tree.

Persistent memory (PM) based indexing techniques have been proposed to build fast yet persistent indexes that sit on the memory bus. Over the past decade, numerous techniques have been proposed with various assumptions and different properties (e.g., some of them were proposed before real PM became available), making it hard for researchers and practitioners to gain a comprehensive understanding of the area. In this tutorial, we give a comprehensive overview of PM indexing techniques, covering both range and hash indexes. We contrast the designs proposed before and after real PM became available, summarize the common and useful design techniques, and discuss potential future challenges and opportunities in this area.

Scalable persistent memory (PM) has opened up new opportunities for building indexes that operate and persist data directly on the memory bus, potentially enabling instant recovery, low latency and high throughput. When real PM hardware (Intel Optane Persistent Memory) first became available, previous work evaluated PM indexes proposed in the pre-Optane era. Since then, newer indexes based on real PM have appeared, but it is unclear how they compare to each other and to previous proposals, and what further challenges remain. This paper addresses these issues by analyzing and experimentally evaluating state-of-the-art PM range indexes built for real PM. We find that newer designs inherited past techniques with new improvements, but do not necessarily outperform pre-Optane era proposals. Moreover, PM indexes are often very competitive with or even outperform indexes tailored for DRAM, highlighting the potential of using a unified design for both PM and DRAM. Functionality-wise, these indexes still lack good support for variable-length keys and handling NUMA effect. Based on our findings, we distill new design principles and highlight future directions.

Data is often stored in a database management system (DBMS) but dataframe libraries are widely used among data scientists. An important but challenging problem is how to bridge the gap between databases and dataframes. To solve this problem, we present ConnectorX, a client library that enables fast and memory-efficient data loading from various databases to different dataframes. We first investigate why the loading process is slow and consumes large memory. We surprisingly find that the main overhead comes from the client-side rather than query execution or data transfer. We integrate several existing and new techniques to reduce the overhead and carefully design the system architecture and interface to make ConnectorX easy to extend to various databases and dataframes. Moreover, we propose server-side result partitioning that can be adopted by DBMSs in order to better support exporting data to data science tools. We conduct extensive experiments to evaluate ConnectorX and compare it with popular libraries. The results show that ConnectorX significantly outperforms existing solutions. ConnectorX is open sourced at: https://github.com/sfu-db/connector-x.

Aim This study aimed to explore the risk factors of submucosal invasion in early colorectal cancer (ECC), so as to provide more accurate treatment strategies for ECC patients. Methods We retrospectively enrolled patients with ECC who received endoscopic or surgical treatment at the First Affiliated Hospital of Wannan Medical College, from January 2017 to December 2021. Univariate analysis and multivariate Logistic regression analysis were used to explore the risk factors of submucosal invasion in ECC. We used a receiver operating characteristic (ROC) curve to estimate the predictive value of independent risk factors for the risk of submucosal invasion in ECC. Results A total of 109 ECC patients were enrolled, among them, 46 cases (42.20%) with infiltration depth of submucosa were classified as the study group, and the remaining 63 cases without submucosal invasion were classified as the control group. Univariate analysis showed that age ≥ 65 years old, lesion diameter > 1cm, differentiation degree, lesion surface accompanied by erosion or ulceration, redness and bleeding tendency were associated with submucosal invasion of ECC (P

Modern database applications often change their schemas to keep up with the changing requirements. However, support for online and transactional schema evolution remains challenging in existing database systems. Specifically, prior work often takes ad hoc approaches to schema evolution with 'patches' applied to existing systems, leading to many corner cases and often incomplete functionality. Applications therefore often have to carefully schedule downtimes for schema changes, sacrificing availability. This paper presents Tesseract, a new approach to online and transactional schema evolution without the aforementioned drawbacks. We design Tesseract based on a key observation: in widely used multi-versioned database systems, schema evolution can be modeled as data modification operations that change the entire table, i.e., data-definition-as-modification (DDaM). This allows us to support schema almost 'for free' by leveraging the concurrency control protocol. By simple tweaks to existing snapshot isolation protocols, on a 40-core server we show that under a variety of workloads, Tesseract is able to provide online, transactional schema evolution without service downtime, and retain high application performance when schema evolution is in progress., To appear at Proceedings of the 2023 International Conference on Very Large Data Bases (VLDB 2023)

Byte-addressable persistent memory (PM) brings hash tables the potential of low latency, cheap persistence and instant recovery. The recent advent of Intel Optane DC Persistent Memory Modules (DCPMM) further accelerates this trend. Many new hash table designs have been proposed, but most of them were based on emulation and perform sub-optimally on real PM. They were also piecewise and partial solutions that side-stepped many important properties, in particular good scalability, high load factor and instant recovery.

The dioxins (DXN) are a set of pollutants encompass polychlorinated dibenzo-p-dioxin/dibenzofuran (PCDD/F), their emissions from municipal waste incineration processes (MSWI) are normally detected under steady operating conditions. However, limited studies have focused on the PCDD/F emission characteristics under a complete maintenance operating period (CMOP), which includes shut-down, cooling, maintenance, heating, startup, and normal operations. In this article, the shutdown process (SDP) starts from the normal operation, followed by shutdown, and then cooling; while the startup process (SUP) commences from heating, followed by startup, and then normal operation. The detection and analysis were conducted at the SDP and SUP stages. The PCDD/F mass and total toxic equivalent quantity (TEQ) concentrations were measured in the flue gas and bag filter fly ash (BF-FA) during a CMOP of Beijing MSWI plant. The highest PCDD/F concentrations in the flue gas were found in the "cooling" and "startup" phases; in the FA, this condition occurred in the "startup" phase. Further, the results show that the most heightened concentrations were observed for 5-6 chlorinated PCDF and 4-5 chlorinated PCDD among the 17 PCDD/F congeners in most cases. More importantly, the air pollution control devices (APCDs) which include activated carbon, lime, and BF, have high removal efficiency for PCDD/F (especially PCDD) during the "startup" phase. APCDs also easily release a considerable amount of PCDD/F because of the memory effect, which emits more PCDD/F at the "shutdown" phase than at the "startup" one. Besides, the annual PCDD/F emission in the flue gas of the MSWI plant was estimated to be 67.72 mg I-TEQ, of which the emission accounts for approx. 20% during the CMOP. Moreover, the experiment shows that the PCDD/F emissions of the MSWI plant in Beijing under unsteady conditions are more miniature than those reported earlier in other areas.

Chemo-photothermal treatment is one of the most efficient strategies for cancer therapy. However, traditional drug carriers without near-infrared absorption capacity need to be loaded with materials behaving photothermal properties, as it results in complicated synthesis process, inefficient photothermal effects and hindered NIR-mediated drug release. Herein we report a facile synthesis of a polyethylene glycol (PEG) linked liposome (PEG-liposomes) coated doxorubicin (DOX)-loaded ordered mesoporous carbon (OMC) nanocomponents (PEG-LIP@OMC/DOX) by simply sonicating DOX and OMC in PEG-liposomes suspensions. The as-obtained PEG-LIP@OMC/DOX exhibits a nanoscale size (600 ± 15 nm), a negative surface potential (−36.70 mV), high drug loading (131.590 mg/g OMC), and excellent photothermal properties. The PEG-LIP@OMC/DOX can deliver loaded DOX to human MCF-7 breast cancer cells (MCF-7) and the cell toxicity viability shows that DOX unloaded PEG-LIP@OMC has no cytotoxicity, confirming the PEG-LIP@OMC itself has excellent biocompatibility. The NIR-triggered release studies demonstrate that this NIR-responsive drug delivery system enables on-demand drug release. Furthermore, cell viability results using human MCF-7 cells demonstrated that the combination of NIR-based hyperthermal therapy and triggered chemotherapy can provide higher therapeutic efficacy than respective monotherapies. With these excellent features, we believe that this phospholipid coating based multifunctional delivery system strategy should promote the application of OMC in nanomedical applications.