由于某一列的数据类型都是相同的,针对于数据存储更容易进行数据压缩,每一列选择更优的数据压缩算法,大大提高了数据的压缩比重; 由于数据压缩比更好,一方面节省了磁盘空间,另一方面对于cache也有了更大的发挥空间 DBMS的功能:几乎覆盖了标准SQL的大部分语法,包括DDL和DML,以及配套的各种函数,用户管理及权限管理,数据的...
copr_cache_hit_ratio: 0.62, distsql_concurrency: 15} | data:TableFullScan_24 | 58.6 MB | N/A | | └─TableFullScan_24 | 90000.00 | 90000 | cop[tikv] | table:t2 | tikv_task:{proc max:31ms, min:0s, avg: 13ms, p80:19ms, p95:26ms, iters:181, tasks:24}, scan_detail: ...
sql="SELECT `L_ORDERKEY`, COUNT(*) AS `count(*)` FROM `lineitem` AS `lineitem` GROUP BY `L_ORDERKEY`"): rowcount =2508.0, cumulativecost=value=2.4860068E7, cpu =105038.0, memory =29796.0, io =201.0, net =4.75, id =109|
copr_cache_hit_ratio:cop task 请求的 Coprocessor Cache 缓存命中率。Coprocessor Cache 配置。 rpc_info:按照向 TiKV 发送 RPC 请求的类型统计总数量和总时间。 backoff:包含不同类型的 backoff 以及等待总耗时。 Insert Insert 算子可能包含以下执行信息: ...
/* default behavior: look it up in the catalogs */ result = get_rel_name(indexId); if (result == NULL) elog(ERROR, "cache lookup failed for index %u", indexId); } return result;}/* * Show buffer usage details. */static voidshow_buffer_usage(ExplainState *es, const BufferUsage ...
evaluated only once for each set of differentvalues of the variables from its outer context. For UNCACHEABLE SUBQUERY, thesubquery is re-evaluated for each row of the outer context. Cacheability ofsubqueries is subject to the restrictions detailed in Section 7.9.3.1, “How theQuery Cache ...
个人认为,项目上线,标志着一个项目真正的开始。从运维,到反馈,到再分析,再版本迭代,再优化… 这是一个漫长且考验耐心的过程。在这个过程中,作为数据存储的关键–>数据库的优化起到尤为重要的作用。 语文学的不好,废话也不多说,下面结合实例咱们说说MYSQL需要从哪些方面进行优化。
If the duration is long, the cache may not be hit. Create split reader cost: the duration that is taken to open a file. If the duration is long, the metadata of the file does not hit the cache. If this occurs, the I/O overhead is high. Get result cost: the duration from ...
2µs, rocksdb: {delete_skipped_count: 97368, key_skipped_count: 236847, block: {cache_hit_count: 3509}}} | keep order:false | N/A | N/A | +---+---+---+---+---+---
configure-memory-usage.md configure-placement-rules.md configure-store-limit.md configure-time-zone.md constraints.md control-execution-plan.md coprocessor-cache.md correlated-subquery-optimization.md cost-model.md credits.md daily-check.md data-type-date-and-time.md data-type-default-values.md dat...