traditional data processing applications, we know the entire dataset in advance, e.g. tables stored in a database. A data stream is a data set that is produced incrementally over time, rather than being available not know when the stream ends. 3 Vasiliki Kalavri | Boston University 2020 DW DBMS SDW DSMS Database Management System • ad-hoc queries, data manipulation tasks • insertions, updates, deletions obtain the synopsis of the whole stream 30 Vasiliki Kalavri | Boston University 2020 Synopsis maintenance & Stream Query Processing Engine Synopsis for R1 Synopsis for Rr … Query Q(R1, …,

degradation. 7 ??? Vasiliki Kalavri | Boston University 2020 DSMS with load shedder 8 Synopsis Maintenance Synopsis for S1 Synopsis for Sr … Fast approximate answers … S1 S2 Sr Input Manager

entire dataset. 2 Synopsis: a lossy, compact summary of the input stream input stream synopsis maintenance component user queries approximate results ??? Vasiliki Kalavri | Boston University 2020 A

userSentPayment 4 Connecting producers to consumers • Indirectly • Producer writes to a file or database • Consumer periodically polls and retrieves new data • polling overhead, latency? • Consumer Databases • DBs keep data until explicitly deleted while MBs delete messages once consumed. • Use a database for long-term data storage! • MBs assume a small working set. If consumers are slow, throughput multiple systems • a Google Compute Engine instance can write logs to the monitoring system, to a database for later querying, and so on. • Data streaming from various processes or devices • a residential

Kalavri | Boston University 2020 ESL: Expressive Stream Language • Ad-hoc SQL queries • Updates on database tables • Continuous queries on data streams • New streams (derived) are defined as virtual views of the 10th international conference on Database Theory (ICDT’05). • Yan-Nei Law, Haixun Wang, and Carlo Zaniolo. Query languages and data models for database sequences and data streams. In Proceedings

operations 30 / 79 Output Operations (1/4) ▶ Push out DStream’s data to external systems, e.g., a database or a file system. ▶ foreachRDD: the most generic output operator • Applies a function to each stream as a table that is being continuously appended. ▶ Built on the Spark SQL engine. ▶ Perform database-like query optimizations. 56 / 79 Programming Model (1/2) ▶ Two main steps to develop a Spark

management • checkpointing state to remote and persistent storage, e.g. a distributed filesystem or a database system • Available state backends in Flink: • In-memory • File system • RocksDB State backends

persistent message queue, before it is processed by Apache Flink, which then writes the results to a database or calls a downstream system. In such a pipeline, latency can be introduced at each stage and for

context of streaming? • queries run continuously • streams are unbounded • In traditional ad-hoc database queries, the query plan is generated on- the-fly. Different plans can be used for two consecutive

PartitionOBucket级C 并DMerge-On-Rea- Mkh取 支持I量P取便于进一 步数RTransform I量h Apache Iceberg asic Data Metadata Database Table Partition Spec Manifest File TableMetadata Snapshot Current Table Version Pointer Apac2e