在postgreSQL中启用查询缓存以提高性能

My application is very database intensive so I'm trying to reduce the load on the database. I am using PostgreSQL as rdbms and python is the programming language. To reduce the load I am already using a caching mechanism in the application. The caching type I used is a server cache, browser cache. Currently I'm tuning the PostgreSQL query cache to get it in line with the characteristics of queries being run on the server.

我的应用程序是数据库密集型的，所以我试图减少数据库的负载。我使用PostgreSQL作为rdbms, python是编程语言。为了减少负载，我已经在应用程序中使用了缓存机制。我使用的缓存类型是服务器缓存，浏览器缓存。目前，我正在调优PostgreSQL查询缓存，使其符合正在服务器上运行的查询的特征。

Questions:

问题:

Is it possible to fine tune query cache on a per database level?
是否可以对每个数据库级别的查询缓存进行微调?
Is it possible to fine tune query cache on a per table basis?
是否可以根据每个表对查询缓存进行微调?
please provide tutorial to learn query cache in PostgreSQL.
请提供在PostgreSQL中学习查询缓存的教程。

1 个解决方案

#1

-1

I developed a system for caching results, to speed-up results queried from a web-based solution. I reproduced below in essence what it did:

我开发了一个缓存结果的系统，以加速从基于web的解决方案查询的结果。我从本质上复制了它所做的:

The following are the generic caching handling tables and functions.

下面是通用缓存处理表和函数。

CREATE TABLE cached_results_headers (
  cache_id serial NOT NULL PRIMARY KEY,
  date timestamptz NOT NULL DEFAULT CURRENT_TIMESTAMP,
  last_access timestamptz NOT NULL DEFAULT CURRENT_TIMESTAMP,
  relid regclass NOT NULL,
  query text NOT NULL,
  rows int NOT NULL DEFAULT 0
  );
CREATE INDEX ON cached_results_headers (relid, md5(query));

CREATE TABLE cached_results (
  cache_id int NOT NULL,
  row_no int NOT NULL  
  );

CREATE OR REPLACE FUNCTION f_get_cached_results_header (p_cache_table text, p_source_relation regclass, p_query text, p_max_lifetime interval, p_clear_old_data interval) RETURNS cached_results_headers AS $BODY$
DECLARE
  _cache_id int;
  _rows int;
BEGIN
  IF p_clear_old_data IS NOT NULL THEN
    DELETE FROM cached_results_headers WHERE date < CURRENT_TIMESTAMP - p_clear_old_data;
  END IF;

  _cache_id := cache_id FROM cached_results_headers WHERE relid = p_source_relation AND md5(query) = md5(p_query) AND query = p_query AND date > CURRENT_TIMESTAMP - p_max_lifetime;
  IF _cache_id IS NULL THEN
    INSERT INTO cached_results_headers (relid, query) VALUES (p_source_relation, p_query) RETURNING cache_id INTO _cache_id;
    EXECUTE $$ INSERT INTO $$||p_cache_table||$$ SELECT $1, row_number() OVER (), r.r FROM ($$||p_query||$$) r $$ USING _cache_id;
    GET DIAGNOSTICS _rows = ROW_COUNT;
    UPDATE cached_results_headers SET rows = _rows WHERE cache_id = _cache_id;
  ELSE
    UPDATE cached_results_headers SET last_access = CURRENT_TIMESTAMP;
  END IF;
  RETURN (SELECT h FROM cached_results_headers h WHERE cache_id = _cache_id);
END;
$BODY$ LANGUAGE PLPGSQL SECURITY DEFINER;

The following is an example of how to use the tables and functions above, for a given view named my_view with a field key to be selected within a range of integer values. You would replace all the following with your particular needs, and replace my_view with either a table, a view, or a function. Also replace the filtering parameters as required.

下面是一个如何使用上面的表和函数的示例，用于一个名为my_view的给定视图，该视图的字段键将在一个整数值范围内选择。您将用您的特定需求替换所有以下内容，并将my_view替换为一个表、一个视图或一个函数。还可以根据需要替换过滤参数。

CREATE VIEW my_view AS SELECT ...; -- create a query with your data, with one of the integer columns in the result as "key" to filter by

CREATE TABLE cached_results_my_view (
  row my_view NOT NULL,
  PRIMARY KEY (cache_id, row_no),
  FOREIGN KEY (cache_id) REFERENCES cached_results_headers ON DELETE CASCADE
  ) INHERITS (cached_results);

CREATE OR REPLACE FUNCTION f_get_my_view_cached_rows (p_filter1 int, p_filter2 int, p_row_from int, p_row_to int) RETURNS SETOF my_view AS $BODY$
DECLARE
  _cache_id int;
BEGIN
  _cache_id := cache_id 
    FROM f_get_cached_results_header('cached_results_my_view', 'my_view'::regclass,
                                     'SELECT r FROM my_view r WHERE key BETWEEN '||p_filter1::text||' AND '||p_filter2::text||' ORDER BY key',
                                     '15 minutes'::interval, '1 day'::interval); -- cache for 15 minutes max since creation time; delete all cached data older than 1 day old

  RETURN QUERY
    SELECT (row).*
    FROM cached_results_my_view
    WHERE cache_id = _cache_id AND row_no BETWEEN p_row_from AND p_row_to
    ORDER BY row_no;
END;
$BODY$ LANGUAGE PLPGSQL;

Example: Retrieve rows from 1 to 2000 from cached my_view results filtered by key BETWEEN 30044 AND 10610679. Run a first time and the results of the query will be cached into table cached_results_my_view, and the first 2000 records will be returned. Run it again shortly after and the results will be retrieved from the table cached_results_my_view directly without executing the query.

示例:从缓存的my_view结果中检索1到2000行，这些结果由30044到106106679之间的key过滤。第一次运行，查询的结果将缓存到表cached_results_my_view中，并返回第一个2000条记录。稍后再运行它，结果将直接从表cached_results_my_view中检索，而不需要执行查询。

SELECT * FROM f_get_my_view_cached_rows(30044, 10610679, 1, 2000);

#1

-1