rows Data Stream Management System • continuous queries • sequential data access, high-rate append-only updates Data Warehouse • complex, offline analysis • large and relatively static and Data persistent relations streams Data Access random sequential, single-pass Updates arbitrary append-only Update rates relatively low high, bursty Processing Model query-driven / pull-based data-driven collection of IP addresses accessing a web server 12 With some practical value for use-cases with append-only data It preserves all history without the option to discard old events Vasiliki Kalavri |

New streams (derived) are defined as virtual views in SQL • Semantics are equivalent to having an append-only table to which new tuples are continuously added. 34 Vasiliki Kalavri | Boston University itemID, start_price, start_time FROM OpenAuction WHERE start_price > 1000 Derived stream as an append- only table. 35 Vasiliki Kalavri | Boston University 2020 User-Defined Aggregates (UDAs) Constructs operations for each new arriving tuple: 1. Append the encoded new tuple to IN, 2. Copy IN to TAPE, and compute F(IN) − OUT 3. Return the result obtained in 2 and append it to OUT. Non-blocking 46 Vasiliki

updates the result. 57 / 79 Programming Model (2/2) 58 / 79 Output Modes ▶ Three output modes: 1. Append: only the new rows appended to the result table since the last trigger will be written to the external can be updated in place, such as a MySQL table. 59 / 79 Output Modes ▶ Three output modes: 1. Append: only the new rows appended to the result table since the last trigger will be written to the external can be updated in place, such as a MySQL table. 59 / 79 Output Modes ▶ Three output modes: 1. Append: only the new rows appended to the result table since the last trigger will be written to the external

approach and durably store all events in a sequential (possibly partitioned) log • A log is an append-only sequence of records on disk • a producer generates messages by simply appending them to the