频繁更新的列不适合建立过多索引 频繁更新的列不适合建立过多索引 应用优化 应用优化 索引建立原则（二） 索引建立原则（二）  order by order by 字句中的字段， 字句中的字段， where where 子句中字段，最常用的 子句中字段，最常用的 sql sql 线实时 系统建议控制在 系统建议控制在 55 个以内。 个以内。  索引不仅能提高查询 索引不仅能提高查询 SQL SQL 性能，同时也可以提高带 性能，同时也可以提高带 where where 字句 字句 的 的 update update ， ， Delete SQL Delete SQL 性能。 性能。  Decimal Decimal 类型字段不要单独建立为索引，但覆盖索引可以 可能会有更好的性能。 可能会有更好的性能。 应用优化 应用优化 编写高效的 编写高效的 SQL SQL （一） （一）  能够快速缩小结果集的 能够快速缩小结果集的 WHERE WHERE 条件写在前面，如果有恒量条件， 条件写在前面，如果有恒量条件， 也尽量放在前面 也尽量放在前面  尽量避免使用 尽量避免使用 GROUP BY GROUP

Conversions between sys_time and local_time are usually uncontroversial, but there are a few cases where things get tricky! (Spoiler alert: it’s all Daylight Saving Time’s fault)40 sys_time and local_time Zone: Africa/Bissau Zone: Africa/Blantyre Zone: Africa/Brazzaville Zone: Africa/Bujumbura …46 Where does this data come from? • The Standard describes these facilities as interfacing with IANA database really like to avoid adding that requirement... • Find an alternate source for the data This is where we settled!48 The MSVC story for time zone data We had a few options... • Ship the entire IANA

supporting new OS versions BRACE YOURSELVES AUTUMN IS HERE nativescript-dev-appium@3.0.0 Where We Are Where We Are Continuous Integration system scales greatly Aware of issues in 10 to 30 min per app

algorithms • Efficient interoperability with coroutines • An open and extensible way to specify where, how, and when work should happen … including some standard ones: an event loop, portable access com/ericniebler/executors_demo_code_cppcon_2021.git119 DEMO TIME (with huge shoutout to Kirk Shoop)120 Where to now?121 WHAT’S TO COME P2300 “std::execution”, currently on track for C++23, brings: • the concepts

Считаем для счётчика топ-10 рефереров за неделю. SELECT Referer, count(*) AS count FROM hits WHERE CounterID = 1234 AND Date >= today() - 7 GROUP BY Referer ORDER BY count DESC LIMIT 10 Типичный

components and utilities to help simplify Qt app development • Can plug and play various UI pieces • Where: - https://github.com/Esri/arcgis-runtime-toolkit-qt • How: - Clone the repository and import the

赚钱盈利。建立一个好的平台，尽量粘住用户 代码：可能开源，可能不开源，绝大部分不开源。 数据？完全封闭。 ➔ 数据是护城河，是信息时代的石油。 互联网企业的发展模式 Web3? So-called Web3 ？ Where is the Next Stage ★ Blockchain ★ Decentralized Ledger Storage: MPT (Merkle Patricia Tree) ★ K-V

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• Environments and toolsA Modern Take on Accidental Complexity • Yak Shaving - the phenomenon where one task leads to another, which leads to another, until you end up working on something that seems

performance Avoids costly abstractions What the vendor providesA quick note on the details in this talk. Where is the process boundary? Focus on in-process interoperability.Run down of some approaches Just be