-- First, let's get the OID of the 'public' namespace that our table lives in - you need -- to run this in the 'blogdb' database, otherwise you'll get the OID of the 'public' -- namespace for the database you're currently connected to. blogdb=# select to_regnamespace('pub...
RELSEG_SIZE requires an initdb. */#defineRELSEG_SIZE131072 存储管理器 在Postgres 中,在对表文件管理和操作时,提供了存储管理器(SMGR)的抽象,由于历史原因,早期的系统中,可能存在不同的存储系统,比如磁盘(magnetic disk)、索尼光盘(Sony WORM optical disk jukebox)、持久化主存(persistent main memory)等。 ...
postgres=# select*frompage_header(get_raw_page('t',0));lsn|checksum|flags|lower|upper|special|pagesize|version|prune_xid---+---+---+---+---+---+---+---+---1/8CA839B0|0|0|824|1792|8192|8192|4|0(1row) get_raw_page是插件实现的方法,接收两个参数,分别是表名和 page 编号...
The final merge is then performed * on-the-fly as the caller repeatedly calls tuplesort_getXXX; this * saves one cycle of writing all the data out to disk and reading it in. 相应代码: for (;;) { /* * On the first iteration, or if we have read all the runs from the * input...
postgres=# create table t as select generate_series(1,100)a; 我这里创建了一个对应的插件,并且创建了一个表。 然后可以通过 pageinspect 插件的一些函数查看表所属的 page 的数据信息: postgres=# select * from page_header(get_raw_page('t', 0)); ...
SELECT datname, temp_files AS"Temporary files",temp_bytes AS"Size of temporary files"FROM pg_stat_database ; 临时文件是按后端或会话连接存储的文件,它们可用作资源池或缓冲区。这些文件与共享资源空间分开存储。 重要提示:视图 pg_stat_database 中的 temp_files 和 temp_bytes 列收集聚合中的统计信息(...
Postgres-XL 10.1搭建 1、简介 Postgres-XL 一款开源的PG集群软件,XL代表eXtensible Lattice,即可扩展的PG“格子”之意。它是一个完全满足ACID的、开源的、可方便进行水平扩展的、多租户安全的、基于PostgreSQL的数据库解决方案。 与Pgpool
EXPLAIN (analyze): buffers on by defaultpg_stat_io: input/output statistics in bytes instead of pagespg_stat_io: WAL statisticspg_stat_get_backend_io: I/O statistics for a specific processVACUUM(verbose): visibility map informationTotal vacuum and analysis time per tableautovacuum: change the ...
Postgres' BYTEA data type can store up to 1 GB of binary data. Above that limit use Large Object (these are stored in a separate table). What are the challenges while migrating from Oracle to Postgres? In this section, we discuss some of the challenges we might face...
fasttrunmodule provides transaction unsafe function to truncate temporary tables without growing pg_class size outer temp table,不造成pg_class, pg_attribute的变更。 目前PG的temp table是会话级,每次使用都会擦写pg_class, pg_attribute,产生系统表垃圾。需要autovacuum自动回收这些垃圾。