SET allow_experimental_query_cache = true 然后在需要缓存的查询后面带上: 代码语言:javascript 复制 SETTINGS use_query_cache = true 例如第一次执行,会生成查询结果缓存: 代码语言:javascript 复制 SELECT RegionID, uniq(UserID) AS u FROM hits_100m_obfuscated GROUP BY RegionID ORDER BY u DESC LIMIT...
首先从Cache设计层面来看,Elasticsearch的Cache包括Query Cache, Request Cache,Data Cache,Index Cache,从查询结果到索引扫描结果层层的Cache加速,就是因为Elasticsearch认为它的场景下存在热点数据,可能被反复查询。反观ClickHouse,只有一个面向IO的UnCompressedBlockCache和系统的PageCache,为什么呢?因为ClickHouse立足于分析查询...
Provide quick answer and avoid excessive computations if the same query is requested more than once in a short period of time. (Un)marked checkboxes refer to #43797 Requirements A setting (all settings are on query level) for tuneable cache usage with three options: - don't use cache; -...
import requests def query_clickhouse(query): response = requests.post("http://localhost:8123", json={"query": query}) return response.json()["result"] # 使用外部缓存系统 cached_result = get_from_cache("my_query") if cached_result is None: result = query_clickhouse("SELECT * FROM my_...
CompiledExpressionCacheCount已编译并保存在缓存中的表达式的数量 jemalloc.*jemalloc相关指标，需要深入理解...
system.query_log 查询执行的信息。已执行查询的信息,例如开始时间、处理持续时间、错误消息。不包含 INSERT 语句,可以在config.xml里设置query_log,可以通过setting log_queries = 0关闭,不会自动删除记录,可以设置ttl属性的表。通过SYSTEM FLUSH LOGS可以强制刷写。每个查询在 query_log 表中创建1~2行,具体取决于...
| `-- cachedir |-- chproxy |-- config | `-- config.yml |-- logs | `-- chproxy.out `-- startup.sh 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 第二步: 配置chproxy: log_debug: false # debug日志 hack_me_please: true ...
1.query_log 作用:ClickHouse开启慢sql查询 开启方法: 打开各个ClickHouse实例的users.xml文件,在默认配置最上层profile(如default)中加入: <log_queries>1</log_queries> service clickhouse-server restart 1. 2. 3. 注意:如添加该参数之后表不自动创建,需要重启clickhouse-server服务。
ast = parseQuery(parser, begin, end, "", max_query_size, settings.max_parser_depth); // 设置query的上下文,比如SETTINGS ... if (async_insert) { ... } else { // 生成interpreter实例 interpreter = InterpreterFactory::get(ast, context, SelectQueryOptions(stage).setInternal(internal)); ...
// src/Parsers/parseQuery.cppASTPtrtryParseQuery(){// 将SQL拆分为token流Tokenstokens(query_begin, all_queries_end, max_query_size);IParser::Postoken_iterator(tokens, max_parser_depth);// 将token流解析为语法树ASTPtr res;constboolparse_res = parser.parse(token_iterator, res, expected);return...