CREATE TYPE table_count AS (table_name TEXT, num_rows INTEGER); CREATE OR REPLACE FUNCTION count_em_all () RETURNS SETOF table_count AS ' DECLARE the_count RECORD; t_name RECORD; r table_count%ROWTYPE; BEGIN FOR t_name IN SELECT c.relname FROM pg_catalog.pg_class c LEFT JOIN pg_...
CREATE TYPE table_count AS (table_name TEXT, num_rows INTEGER); CREATE OR REPLACE FUNCTION count_em_all () RETURNS SETOF table_count AS ' DECLARE the_count RECORD; t_name RECORD; r table_count%ROWTYPE; BEGIN FOR t_name IN SELECT c.relname FROM pg_catalog.pg_class c LEFT JOIN pg_...
akendb=# alter table aken01 set (parallel_workers =32); ALTER TABLE akendb=# explain (analyze,buffers,verbose) select count(*) from aken01; QUERY PLAN --- Finalize Aggregate (cost=535899.34..535899.35 rows=1 width=8) (actual time=6150.317..6150.318 rows=1 loops=1) Output: count...
In PostgreSQL, you can easily retrieve the row count for each table in a database. This can be particularly useful for database analysis, monitoring, or reporting. There are a couple of methods to accomplish this, using either SQL queries that interact with PostgreSQL’s system catalog or by...
CREATE OR REPLACE FUNCTION count_em_all (limitNum INTEGER) RETURNS SETOF table_count AS ' DECLARE the_count RECORD; -- 当前行数 t_name RECORD; -- 当前表名 r table_count%ROWTYPE; BEGIN -- 循环所有表,对于每个表进行相关操作。 FOR t_name IN select concat_ws(''.'',''"''||pn.nsp...
select top n * from (select top m * from table_name order by column_name ) a order by column_name desc --查询第N到M条记录。常用的分页也是这种方式。 例如常用的分页方式: declare @page int declare @row int set @page=2 --页数
[ OFFSET start [ ROW | ROWS ] ] [ FETCH { FIRST | NEXT } [ count ] { ROW | ROWS } ONLY ] [ FOR { UPDATE | NO KEY UPDATE | SHARE | KEY SHARE } [ OF table_name [, ...] ] [ NOWAIT | SKIP LOCKED ] [...] ] ...
数据库的维护操作包括VACUUM、CREATE INDEX和ALTER TABLE ADD FOREIGN KEY等操作。按需使用maintenance_work_mem设置的内存, 当有并发的创建索引和autovacuum等操作时可能造成内存消耗过度，这时需要设置参数vacuum_cost_delay（VACUUM操作比较消耗IO，设置延时是指VACUUM操作消 耗的成本大于vacuum_cost_limit后延迟10毫秒再...
CREATE[ORREPLACE]FUNCTIONname([[argmode][argname]argtype[{DEFAULT|=}default_expr][,...]])[RETURNSrettype|RETURNSTABLE(column_name column_type[,...])]{LANGUAGElang_name|TRANSFORM{FORTYPEtype_name}[,...]|WINDOW|IMMUTABLE|STABLE|VOLATILE|[NOT]LEAKPROOF|CALLEDONNULLINPUT|RETURNSNULLONNULLINPUT|...
createdatabaseperformance_test;createtabletest_tbl(idserialprimarykey,created_attimestamp,contentvarchar(512)); 生成测试数据 使用generate_series 函数生成自增 ID,使用 now() 函数生成 created_at 列,对于 content 列,使用了 repeat(md5(random()::text), 10) 生成 10 个 32 位长度的 md5 字符串。使用...