The traditional and well-established cost-based query optimizer approach enumerates different execution plans for each query, assesses each plan with costs, and selects the plan that promises the lowest costs for execution. However, the optimal execution plan is not always selected. To steer the optimizer in the right direction, many query optimizers provide configuration parameters called query optimizer hints. These hints can be set for every single query separately. To show the great potential of these hints for the optimization of analytical queries, we present results of a comprehensive and in-depth evaluation using three benchmarks and two different versions of the open-source database system PostgreSQL. In particular, we highlight that query optimizer hinting is a non-trivial challenge. To solve this challenge, we propose FASTgres , a learning-based context-aware classification strategy for hint set prediction. Compared to related work, FASTgres provides transparent and direct hint set predictions with consistent performance improvements. In our end-to-end evaluation, we demonstrate that FASTgres effectively reduces benchmark runtimes by a factor of up to 3.25x with only steering the cost-based optimizer.

In this demo, we present PostCENN , an enhanced PostgreSQL database system with an end-to-end integration of machine learning (ML) models for cardinality estimation. In general, cardinality estimation is a topic with a long history in the database community. While traditional models like histograms are extensively used, recent works mainly focus on developing new approaches using ML models. However, traditional as well as ML models have their own advantages and disadvantages. With PostCENN , we aim to combine both to maximize their potentials for cardinality estimation by introducing ML models as a novel means to increase the accuracy of the cardinality estimation for certain parts of the database schema. To achieve this, we integrate ML models as first class citizen in PostgreSQL with a well-defined end-to-end life cycle. This life cycle consists of creating ML models for different sub-parts of the database schema, triggering the training, using ML models within the query optimizer in a transparent way, and deleting ML models.

For many tasks in market research it is important to model customers and products as comparable instances. Usually, the integration of customers and products into one model is not trivial. In this paper, we will detail an approach for a combined vector space of customers and products based on word embeddings learned from receipt data. To highlight the strengths of this approach we propose four different applications: recommender systems, customer and product segmentation and purchase prediction. Experimental results on a real-world dataset with 200M order receipts for 2M customers show that our word embedding approach is promising and helps to improve the quality in these applications scenarios.