ART: sub-logarithmic decentralized range query processing with probabilistic guarantees

Range queries are important in many diverse applications. In its simplest one-dimensional form, a range query is expressed by an interval [a, b] on the real line, whereas the answer consists of all elements e in [a, b]. In this work, we focus on efficient range query processing techniques in the Apache Spark engine, which is the state-of-the-art solution for big data management and analytics. We aim at developing a Spark-based indexing scheme that supports range queries in such large-scale decentralized environments and scale well w.r.t. the number of nodes and the data items stored. Towards this goal, there have been solutions in the last few years, which however turn out to be inadequate at the envisaged scale, since the classic linear or even the logarithmic complexity (for point queries) is still too expensive, whereas range query processing is even more demanding. In this paper, we go one step further and present a solution with sub-logarithmic complexity. In particular, we present SPIS (SPark-based Interpolation Search), a tree structure that outperforms the existing Spark built-in lookup techniques. We carry out an experimental evaluation by using synthetic data sets. Our experimental results demonstrate the efficiency and scalability of the proposed approach.

Multi-dimensional data structures are applied in many real index applications, i.e. data mining, indexing multimedia data, indexing of text documents and so on. Many index structures and algorithms have been proposed. There are two major approaches to multi-dimensional indexing: data structures to indexing metric and vector spaces. R-trees, R*-trees and (B)UB-trees are representatives of the vector data structures. These data structures provide efficient processing of many types of queries, i.e. point queries, range queries and so on. As far as the vector data structures are concerned, the range query retrieves all points in defined hyper box in an n-dimensional space. The narrow range query is an important type of the range query. Its processing is inefficient in vector data structures. Moreover, the efficiency decreases as the dimension of the indexed space increases. We depict an application of the signature for more efficient processing of narrow range queries. The approach puts the signature into the multi-dimensional data structures like R-tree or UB-tree but original functionalities are preserved, i.e. the range query algorithm for general range query. The novel data structure is called the signature data structure, e.g., Signature R-tree or Signature UB-tree.

This work studies the problem of 2-dimensional searching for the 3-sided range query of the form [a, b] x (-∞, c] in both main and external memory, by considering a variety of input distributions. A dynamic linear main memory solution is proposed, which answers 3-sided queries in O(log n + t) worst case time and scales with O (log log n) expected with high probability update time, under continuous μ-random distributions of the x and y coordinates, where n is the current number of stored points and t is the size of the query output. Our expected update bound constitutes a considerable improvement over the O(log n) update time bound achieved by the classic Priority Search Tree of McCreight [23], as well as over the Fusion Priority Search Tree of Willard [30], which requires O(log n/log log n) time for all operations. Moreover, we externalize this solution, gaining O(logBn + t/B) worst case and O(logBlogn) amortized expected with high probability I/Os for query and update operations respectively, where B is the disk block size. Then, combining the Modified Priority Search Tree [27] with the Priority Search Tree [23], we achieve a query time of O(log log n + t) expected with high probability and an update time of O(log log n) expected with high probability, under the assumption that the x-coordinates are continuously drawn from a smooth distribution and the y-coordinates are continuously drawn from a more restricted class of distributions. The total space is linear. Finally, we externalize this solution, obtaining a dynamic data structure that answers 3-sided queries in O(logB log n + t/B) I/Os expected with high probability, and it can be updated in O(logB log n) I/Os amortized expected with high probability and consumes O(n/B) space, under the same assumptions.

Associations of exposure to per- and polyfluoroalkyl substances mixture with the numbers of lymph nodes in colorectal cancer patients

With the increasing popularity of the peer-to-peer (P2P) computing paradigm, many general range query schemes for distributed hash table (DHT)-based P2P systems have been proposed in recent years. Although those schemes can provide range query capability without modifying the underlying DHTs, they have the query delay depending on both the scale of the system and the size of the query space or the specific query, and thus cannot guarantee to return the query results in a bounded delay. In this paper, we propose Armada, an efficient range query processing scheme to support delay-bounded single-attribute and multiple-attribute range queries. It is the first delay-bounded general range query scheme on constant-degree DHTs, and can return the results for any range query within 2logN hops in a P2P system with N peers. Results of analysis and simulations show that the average delay in Armada is less than logN, and the average message cost of single-attribute range queries is about logN+2n 2 (n is the number of peers that intersect with the query). These results are very close to the lower bounds on delay and message cost of range queries over constant-degree DHTs.

ZNS - Efficient query processing with ZurichNoSQL

We address the problem of efficient processing of spatio-temporal range queries for moving objects whose whereabouts in time are not known exactly. The fundamental question tackled by such queries is, given a spatial region and a temporal interval, retrieve the objects that were inside the region during the given interval. As earlier works have demonstrated, when the location, time information is uncertain, syntactic constructs are needed to capture the impact of the uncertainty, along with the corresponding processing algorithms. In this work, we focus on the uncertainty model that represents the whereabouts in-between two known locations as a bead and an uncertain trajectory is represented as a necklace -- a sequence of beads. For each syntactic variant of the range query, we present the respective processing algorithms and, in addition, we propose pruning strategies that speed up the generation of the queries' answers. We also present the experimental observations that quantify the benefits of our proposed methodologies.

Distributed Hash Tables (DHTs) are scalable, self‐organizing, and adaptive to underlying topology changes, thus being a promising infrastructure for hosting large‐scale distributed applications. The ever‐wider use of DHT infrastructures has found more and more applications that require support for range queries. Recently, a number of DHT‐based range query schemes have been proposed. However, most of them suffer from high query delay or imbalanced load distribution. To address these problems, in this paper we first present an efficient indexing structure called Balanced Kautz (BK) tree that uniformly maps the m‐dimensional data space onto DHT nodes, and then propose a BK tree‐based range query scheme called ERQ that processes range queries in a parallel fashion and guarantees to return the results in a bounded delay. In a DHT with N nodes, ERQ can answer any range of query in less than rmlog N(2loglog N + 1) hops in a load‐balanced manner, irrespective of the queried range, the whole space size, or the number of queried attributes. The effectiveness of our proposals is demonstrated through experiments. Copyright © 2010 John Wiley & Sons, Ltd.

Uncertain data has emerged as a key data type in many applications. New and efficient query processing techniques need to be developed due to the inherent complexity of this new type of data. In this paper, we investigate a special type of query, range queries, on uncertain data. We propose a threshold interval indexing structure that aims to balance different time consuming factors to achieve an optimal overall query performance. We also present a more efficient version of our structure which loads its primary tree into memory for faster processing. Experimental results are presented to justify the efficiency of the proposed query processing technique.

BackgroundPatient outcomes in rectal cancer with synchronous liver metastases remain heterogeneous, underscoring the need for reliable prognostic factors to guide individualized treatment strategies. This study sought to assess the influence of lymph node-related indices on the survival of rectal cancer patients with synchronous liver metastases who underwent preoperative chemoradiotherapy and to construct a novel nomogram for this patient population.MethodsData on rectal cancer patients with synchronous liver metastases who underwent preoperative chemoradiotherapy between 2010 and 2019 were retrieved from the Surveillance, Epidemiology, and End Results (SEER) database. X-tile software was employed to determine the optimal cutoff point of lymph node-related indices. The Kaplan-Meier method and log-rank test were used to assess survival differences. Cox univariate and multivariate analyses were conducted to identify the prognostic factors for overall survival (OS). We constructed a novel nomogram to predict individual survival probability. The concordance index (C-index) and calibration curve were used to determine the predictive accuracy and discriminative ability of the nomogram.ResultsA total of 547 rectal cancer patients with synchronous liver metastases were enrolled. The OS of patients with total number of lymph nodes (TLN) <7 was significantly worse than that of patients with TLN ≥7 (3-year OS rate: 46.6% vs. 62.7%; 5-year OS rate: 22.9% vs. 43.8%, P=0.001). Patients with number of positive lymph nodes (PLN) <7 had better OS than that of patients with PLN ≥7 significantly (3-year OS rate: 63.5% vs. 36.0%; 5-year OS rate: 44.1% vs. 12.6%, P<0.001). The 3-year OS rate was 49.7% for patients with number of negative lymph nodes (NLN) <11 compared with 68.6% for patients with NLN ≥11; and the 5-year OS rate was 23.9% and 53.6% for patients with NLN <11 and patients with NLN ≥11, respectively (P<0.001). Multivariate analysis showed that TLN, NLN and PLN were independent prognostic factors for OS [TLN: hazard ratio (HR) =0.571, 95% confidence interval (CI): 0.408–0.799, P=0.001; NLN: HR =0.593, 95% CI: 0.456–0.770, P<0.001; PLN: HR =1.736, 95% CI: 1.201–2.509, P=0.003]. A novel nomogram was established based on the independent prognostic factors indicated in the multivariate Cox analysis. The C-index for prognostic nomogram was 0.67 (95% CI: 0.63–0.71). The calibration plot for the probability of 3-year survival demonstrated an optimal agreement between the predicted and actual survival.ConclusionsLymph node (LN)-related indices are significant prognostic factors for OS in rectal cancer patients with synchronous liver metastases, offering insights into survival prediction and enabling personalized treatment strategies.

Significance of Extranodal Extension of Regional Lymph Nodes in Surgically Resected Non-small Cell Lung Cancer

Purpose: Adequate lymph node analysis is critical for appropriate staging in colorectal cancer. The aim of this study is to determine whether 12 or more nodes recovered in stage III rectal cancer results in improved oncologic outcomes. Methods: Two hundred and forty-eight patients with stage III rectal cancer from 1995 through 2004 were reviewed. They were categorized into 2 subgroups by the number of nodes retrieved (＜12 and ≥12), and oncologic outcomes in terms of 5-year overall and disease-free survival were analyzed for all patients, patients with American Joint Committee on Cancer (AJCC) N1 disease (N=145), and those with AJCC N2 (N=103). Results: Five-year overall and disease-free survival was 79.0% and 58.4%, respectively. There was no significant difference in clincopathologic features between ＜12 retrieval group and ≥12 group. Although there was significant difference in overall survival and disease-free survival between the number (＜12 and ≥12) of lymph nodes removed in N2 disease (P=0.043; P=0.022) in univariate analysis, the total number of lymph nodes retrieved was not a prognostic factor affecting survival in multivariate analysis. The N2 stage and lateral margin involvement were prognostic factors affecting survival in multivariate analysis. Conclusion: This study showed that the total number of lymph nodes analyzed for stage III rectal cancer is not a prognostic factor on overall or disease-free survival in multivariate analysis. (J Korean Surg Soc 2009;77:262-266)

In Asia, esophageal squamous cell carcinoma (ESCC) accounts for more than 90% of esophageal cancer cases and can be treated with minimally invasive esophagectomy (MIE); however, MIE has certain technical limitations in resecting lymph nodes. The advantages of robot-assisted minimally invasive esophagectomy (RAMIE) surgery, such as the high-definition three-dimensional (3D) vision and the presence of the EndoWrist, facilitates movement in challenging anatomical regions. However, few studies have compared the postoperative outcomes between RAMIE with MIE for the lymph node dissection of patients with ESCC. We identified 285 patients with ESCC who underwent surgical resection between January 2019 and April 2023. Of these patients, 270 met the screening criteria and were enrolled in our study. These patients were then divided into two groups according to the thoracic approach: MIE (n=168) or RAMIE cohort (n=102). The aim of this study was to investigate the possible advantages in terms of postoperative outcomes of RAMIE over MIE for thoracic lymph node dissection. Most patients were male (97.4%). According to the pathological-stage of esophageal cancer, 5 (1.9%), 99 (37.1%), 72 (27.0%), 82 (30.7%), and 9 (3.4%) patients were pathological-stage 0, I, II, III, and IV, respectively. The number of regional lymph node resections in the RAMIE cohort was significantly higher than that in the MIE group for the following regions: the left tracheobronchial lymph nodes (106tbL) (P<0.001), paratracheal lymph nodes [106pre] (P=0.011), the sub-longitudinal lymph nodes [107] (P<0.001), the left main bronchial lymph nodes [109L] (P<0.001), the right main bronchial lymph nodes [109R] (P<0.001), the sub-thoracic periesophageal lymph nodes [110] (P=0.004), and the supradiaphragmatic lymph nodes [111] (P<0.001). By comparing MIE cohort with RAMIE cohort, the transthoracic approach with RAMIE yielded a greater total number of thoracic lymph nodes dissected [MIE: mean 20.82, standard deviation (SD) 9.45; RAMIE: mean 26.07, SD 9.28; P<0.001] and a greater total number of lymph node groups that underwent thoracic lymph node dissection (MIE: mean 5.28, SD 1.94; RAMIE: mean 7.29, SD 1.77; P<0.001). Our study shows that RAMIE may be more effective than MIE in terms of the number thoracic lymph nodes dissected and the extent of dissection. Moreover, RAMIE may be not associated with additional surgical complications.

BACKGROUND: The question of what constitutes adequate lymphadenectomy in colorectal cancer has been discussed for several generations without a definitive conclusion being reached. METHODS: Review of the literature. RESULTS: Our guidelines recommend the radical en-bloc resection of the tumor-bearing bowel with central ligation of its vessels, although evidence supporting this is limited. The resection includes a systematic lymphadenectomy of the lymphatic drainage along its arterial blood supply, and should be performed with a no-touch technique. The lymphatic dissection determines the extent of bowel resection, which should include – depending on the tumor infiltration depth (pT) – a 5–10 cm resection margin proximally and distally. The lymph node status (pN) is one of the most important prognostic factors. The calculation of the total number of resected lymph nodes and the lymph node ratio allows greater accuracy in tumor staging and a more precise estimation of prognosis. The total number of lymph nodes can be influenced by the surgeon, the patient, and the pathologist. CONCLUSIONS: New studies exist, which show that only small subgroups of patients receive a prognostic benefit from radical lymphadenectomy. Because we cannot yet identify these patients pre- or intraoperatively, we continue to perform radical lymphadenectomy.

Despite their widespread utilization, little is known about the quality of pathologists' assistants' services. Pathologists' assistants' performance was compared with pathology residents' performance using the metrics of lymph node retrieval and tissue resubmission rates. Lymph node retrieval was calculated by retrospective review of surgical pathology reports from a sample of axillary dissection, mastectomy, and colorectal specimens. Tissue resubmission rates were calculated by retrospective review of a sample of general surgical pathology reports. Pathologists' assistants retrieved a significantly greater total number of lymph nodes compared with pathology residents; however, there was no difference in the total number of positive lymph nodes retrieved. Cases for which pathologists' assistants performed the gross examination had a significantly decreased resubmission rate compared with those performed by residents. In this setting, the gross examination performance of pathologists' assistants was equivalent to or superior to that of pathology residents. These results provide the first information available relating to pathologists' assistants' performance in surgical pathology.