Graph simulation has recently received a surge of attention in graph processing and analytics. In real-life applications, e.g. social science, biology, and chemistry, many graphs are composed of a series of evolving graphs (i.e., temporal graphs). While most of the existing graph generators focus on static graphs, the temporal information of the graphs is ignored. In this paper, we focus on simulating temporal graphs, which aim to reproduce the structural and temporal properties of the observed real-life temporal graphs. In this paper, we first give an overview of the existing temporal graph generators, including recently emerged learning-based approaches. Most of these learning-based methods suffer from one of the limitations: low efficiency in training or slow generating, especially for temporal random walk-based methods. Therefore, we propose an efficient learning-based approach to generate graph snapshots, namely temporal graph autoencoder (TGAE). Specifically, we propose an attention-based graph encoder to encode temporal and structural characteristics on sampled ego-graphs. And we proposed an ego-graph decoder that can achieve a good trade-off between simulation quality and efficiency in temporal graph generation. Finally, the experimental evaluation is conducted among our proposed TGAE and representative temporal graph generators on real-life temporal graphs and synthesized graphs. It is reported that our proposed approach outperforms the state-of-the-art temporal graph generators by means of simulation quality and efficiency.

Most large enterprises build predefined data pipelines and execute them periodically to process operational data using SQL queries for various tasks. A key issue in minimizing the overall makespan of these pipelines is the efficient scheduling of concurrent queries within the pipelines. Existing tools mainly rely on simple heuristic rules due to the difficulty of expressing the complex features and mutual influences of queries. The latest reinforcement learning (RL) based methods have the potential to capture these patterns from feedback, but it is non-trivial to apply them directly due to the large scheduling space, high sampling cost, and poor sample utilization. Motivated by these challenges, we propose BQSched, a non-intrusive Scheduler for Batch concurrent Queries via reinforcement learning. Specifically, BQSched designs an attention-based state representation to capture the complex query patterns, and proposes IQ-PPO, an auxiliary task-enhanced proximal policy optimization (PPO) algorithm, to fully exploit the rich signals of Individual Query completion in logs. Based on the RL framework above, BQSched further introduces three optimization strategies, including adaptive masking to prune the action space, scheduling gain-based query clustering to deal with large query sets, and an incremental simulator to reduce sampling cost. To our knowledge, BQSched is the first non-intrusive batch query scheduler via RL. Extensive experiments show that BQSched can significantly improve the efficiency and stability of batch query scheduling, while also achieving remarkable scalability and adaptability in both data and queries. For example, across all DBMSs and scales tested, BQSched reduces the overall makespan of batch queries on TPC-DS benchmark by an average of 34% and 13%, compared with the commonly used heuristic strategy and the adapted RL-based scheduler, respectively. The source code of BQSched is available at https://github.com/chxu2000/BQSched.

Graph generation plays an essential role in understanding the formation of complex network structures across various fields, such as biological and social networks. Recent studies have shifted towards employing deep learning methods to grasp the topology of graphs. Yet, most current graph generators fail to adequately capture the community structure, which stands out as a critical and distinctive aspect of graphs. Additionally, these generators are generally limited to smaller graphs because of their inefficiencies and scaling challenges. This paper introduces the Community-Preserving Graph Adversarial Network (CPGAN), designed to effectively simulate graphs. CPGAN leverages graph convolution networks within its encoder and maintains shared parameters during generation to encapsulate community structure data and ensure permutation invariance. We also present the Scalable Community-Preserving Graph Attention Network (SCPGAN), aimed at enhancing the scalability of our model. SCPGAN considerably cuts down on inference and training durations, as well as GPU memory usage, through the use of an ego-graph sampling approach and a short-pipeline autoencoder framework. Tests conducted on six real-world graph datasets reveal that CPGAN manages a beneficial balance between efficiency and simulation quality when compared to leading-edge baselines. Moreover, SCPGAN marks substantial strides in model efficiency and scalability, successfully increasing the size of generated graphs to the 10 million node level while maintaining competitive quality, on par with other advanced learning models.