ClickHouse是俄罗斯的Yandex于2016年开源的列式存储数据库(DBMS),使用C++语言编写,主要用于在线分析处理查询(OLAP),能够使用SQL查询实时生成分析数据报告。 OLAP(On-Line Analytical Processing)翻译为联机分析处理,专注于分析处理,从对数据库操作来看,OLAP是对数据的查询; OLTP(on-line transactio
case T_HashJoin: /* try not to be too chatty about this in text mode */ if (es->format != EXPLAIN_FORMAT_TEXT || (es->verbose && ((Join *) plan)->inner_unique)) ExplainPropertyBool("Inner Unique", ((Join *) plan)->inner_unique, es); break; default: break; } /* quals,...
Join method – The method (e.g., hash, sort-merge, etc.) used to join tables with each other. Join type – The type of join (e.g., outer, anti, semi, etc.). Join order – The order in which the tables are joined to each other. Partition pruning – Are...
Flink SQL> EXPLAIN ESTIMATED_COST, CHANGELOG_MODE, PLAN_ADVICE, JSON_EXECUTION_PLAN > SELECT * > FROM alan_ticker2 > MATCH_RECOGNIZE( > PARTITION BY symbol > ORDER BY rowtime > MEASURES > C.price AS lastPrice, > C.rowtime AS rowtime > ONE ROW PER MATCH > AFTER MATCH SKIP PAST LAST ...
1.正在使用所有可用的并行工作进程（max_parallel_workers）。这是一种可能的解释，因为即使使用您显示的...
private static final ConcurrentMap<Class<?>, ExtensionLoader<?>> EXTENSION_LOADERS = new ConcurrentHashMap<>(64); private ExtensionLoader(Class<?> type) { this.type = type; objectFactory = (type == ExtensionFactory.class ? null : ExtensionLoader.getExtensionLoader(ExtensionFactory.class).getAdaptive...
@lysu we don't need to bind different next() functions. we only need to add a if statement in the next() function for every operator to record the executor statistics. and these executor statistics can also be reused in the trace statement. zz-jason added sig/execution and removed compon...
In this article, I'll describe several ways to do this in PostgreSQL 8.4. PostgreSQL 8.4 syntax is much richer than that of MySQL. The former can use the analytic functions, recursive CTE's and proprietary syntax extensions, all of which can be used for this task. Let's create a sample...
{1,\}\)$/\1\t\2/p' rockyou-withcount.txt >ry $ # The following are shell functions to build commands. They will be explained $ # below using examples (I can not express myself well in this language). $ counta() { LC_ALL=C awk 'BEGIN { FS = "\t"; p = 0; a = 0 }...
Has a number of different meanings used to indicate partition elimination may also indicate an actual filter step where one row source is filtering another functions such as min may introduce filter steps into query plans In this example there are 2 filter steps. The first is effectively like a...