74 research outputs found
Weiterentwicklung analytischer Datenbanksysteme
This thesis contributes to the state of the art in analytical database systems. First, we identify and explore extensions to better support analytics on event streams. Second, we propose a novel polygon index to enable efficient geospatial data processing in main memory. Third, we contribute a new deep learning approach to cardinality estimation, which is the core problem in cost-based query optimization.Diese Arbeit trägt zum aktuellen Forschungsstand von analytischen Datenbanksystemen bei. Wir identifizieren und explorieren Erweiterungen um Analysen auf Eventströmen besser zu unterstützen. Wir stellen eine neue Indexstruktur für Polygone vor, die eine effiziente Verarbeitung von Geodaten im Hauptspeicher ermöglicht. Zudem präsentieren wir einen neuen Ansatz für Kardinalitätsschätzungen mittels maschinellen Lernens
Data Management for Data Science - Towards Embedded Analytics
The rise of Data Science has caused an influx of new usersin need of data management solutions. However, insteadof utilizing existing RDBMS solutions they are opting touse a stack of independent solutions for data storage andprocessing glued together by scripting languages. This is notbecause they do not need the functionality that an integratedRDBMS provides, but rather because existing RDBMS im-plementations do not cater to their use case. To solve theseissues, we propose a new class of data management systems:embedded analytical systems. These systems are tightlyintegrated with analytical tools, and provide fast and effi-cient access to the data stored within them. In this work,we describe the unique challenges and opportunities w.r.tworkloads, resilience and cooperation that are faced by thisnew class of systems and the steps we have taken towardsaddressing them in the DuckDB system
Flow-Loss: Learning Cardinality Estimates That Matter
Previous approaches to learned cardinality estimation have focused on
improving average estimation error, but not all estimates matter equally. Since
learned models inevitably make mistakes, the goal should be to improve the
estimates that make the biggest difference to an optimizer. We introduce a new
loss function, Flow-Loss, that explicitly optimizes for better query plans by
approximating the optimizer's cost model and dynamic programming search
algorithm with analytical functions. At the heart of Flow-Loss is a reduction
of query optimization to a flow routing problem on a certain plan graph in
which paths correspond to different query plans. To evaluate our approach, we
introduce the Cardinality Estimation Benchmark, which contains the ground truth
cardinalities for sub-plans of over 16K queries from 21 templates with up to 15
joins. We show that across different architectures and databases, a model
trained with Flow-Loss improves the cost of plans (using the PostgreSQL cost
model) and query runtimes despite having worse estimation accuracy than a model
trained with Q-Error. When the test set queries closely match the training
queries, both models improve performance significantly over PostgreSQL and are
close to the optimal performance (using true cardinalities). However, the
Q-Error trained model degrades significantly when evaluated on queries that are
slightly different (e.g., similar but not identical query templates), while the
Flow-Loss trained model generalizes better to such situations. For example, the
Flow-Loss model achieves up to 1.5x better runtimes on unseen templates
compared to the Q-Error model, despite leveraging the same model architecture
and training data
BitE : Accelerating Learned Query Optimization in a Mixed-Workload Environment
Although the many efforts to apply deep reinforcement learning to query
optimization in recent years, there remains room for improvement as query
optimizers are complex entities that require hand-designed tuning of workloads
and datasets. Recent research present learned query optimizations results
mostly in bulks of single workloads which focus on picking up the unique traits
of the specific workload. This proves to be problematic in scenarios where the
different characteristics of multiple workloads and datasets are to be mixed
and learned together. Henceforth, in this paper, we propose BitE, a novel
ensemble learning model using database statistics and metadata to tune a
learned query optimizer for enhancing performance. On the way, we introduce
multiple revisions to solve several challenges: we extend the search space for
the optimal Abstract SQL Plan(represented as a JSON object called ASP) by
expanding hintsets, we steer the model away from the default plans that may be
biased by configuring the experience with all unique plans of queries, and we
deviate from the traditional loss functions and choose an alternative method to
cope with underestimation and overestimation of reward. Our model achieves
19.6% more improved queries and 15.8% less regressed queries compared to the
existing traditional methods whilst using a comparable level of resources.Comment: This work was done when the first three author were interns in SAP
Labs Korea and they have equal contributio
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