* queryString: original source text of command * context: identifies source of statement (toplevel client command, * non-toplevel client command, subcommand of a larger utility command) * params: parameters to use during execution * dest: where to send results * completionTag: points to a buf...
在PostgreSQL中,使用TRUNCATE命令清理表資料,或使用DROP TABLE刪除表時,可能出現磁碟空間未立即釋放的問題。本文將介紹該現象的原因,並提供排查和解決方案。 問題原因 PostgreSQL執行TRUNCATE和DROP TABLE操作時,系統會在事務提交時對每一個要刪除的檔案進行unlink調用。unlink調用會解除inode的引用,...
postgres=# \h drop tablespace Command: DROP TABLESPACE Description: remove a tablespace Syntax: DROP TABLESPACE [ IF EXISTS ] name 删除表空间前必须要删除该表空间下的所有数据库对象,否则无法删除。 如: postgres=# drop tablespace if exists tbs_test; ERROR: tablespace "tbs_test" is not empty 删除...
Example #2: How Does DROP IF EXISTS Command Work in PostgreSQL? The IF EXISTS is an option that checks the existence of a table. It can be seen from the above example that an error occurs when we tried to drop a table that doesn't exist. We can avoid such an error using the IF ...
command that drops/deletes the existing objects of a database permanently. Using theDROPcommand, you can drop a database, table, trigger, etc. If we talk about theDROP TABLEcommand, it drops an existing table from a database. It not only drops the table but also deletes the table’s ...
restore_command='cp /opt/buxlog/%f %p' 52.重建索引 REINDEX { INDEX | TABLE | DATABASE | SYSTEM } name [ FORCE ] INDEX 重新建立声明了的索引。 TABLE 重新建立声明的表的所有索引。如果表有个从属的"TOAST"表,那么这个表也会重新索引。
postgres-# \help <command_name> 例如,我们查看下 select 语句的语法: postgres=# \help SELECT Command: SELECT Description: retrieve rows from a table or view Syntax: [ WITH [ RECURSIVE ] with_query [, ...] ] SELECT [ ALL | DISTINCT [ ON ( expression [, ...] ) ] ] ...
可以植入到postgresql.conf中的archive_cleanup_command参数中去 关键字解析: %r:%r 会被替换为一个 32 位的十六进制数字,代表当前 PostgreSQL 服务器的最新复制位置。这确保了在清理归档日志时,只有早于当前复制位置的归档日志文件会被删除,而不会删除仍然需要进行复制的文件。
TRUNCATE cannot be used on a table that has foreign-key references from other tables, unless all such tables are also truncated in the same command. Checking validity in such cases would require table scans, and the whole point is not to do one. ...