postgresql数据库支持数据库分表，但是有时会遇到，现场的数据库已经在跑了，但是新的需求，需要增加一个字段，

字段增加，分表会自动增加的，但是规则不会实时更新，规则不更新的话，分表新的字段的值就不会更新掉。

其实只需要把所有的规则修改下就可以了，但是有时规则比较多，手动修改还是有点麻烦，所以，就写了一个函数来

做这个功能，这个使用起来还是很快很方便的，这里使用到的就是游标、函数

-------------该函数只需要主表名称和时间字段，即可针对主表字段有增加、修改、删除的情况时，一键修改规则------------------------------
----------------------------定制项目有时会遇到有分表需要增加字段的情况，但是现场不会重新安装，但是----------------------------------------------------------------
create
or replace function cursor_demo (
	tabname character varying,timefield character varying
) returns refcursor as $body$ declare
	sub_tab_name varchar (1000) ; column_name_desc varchar (1000) ; declare
		fetch_sub_tab_refcursor cursor for select
			tablename
		from
			pg_tables
		where
			tablename like tabname || '_%' ; declare
				fetch_sub_column_refcursor cursor for select
					column_name
				from
					information_schema. columns
				where
					table_name = tabname ; declare
						sql_desc varchar (1000) ; declare
							value_desc varchar (1000) ; declare
								all_sql_desc varchar (2000) ; declare
									st_time varchar (100) ;
								begin
									open fetch_sub_tab_refcursor ; loop fetch fetch_sub_tab_refcursor into sub_tab_name ;
								if found then
 
								if (
									length (tabname) = (length(sub_tab_name) - 7)
								) then
 
								if (
									tabname = (
										substring (
											sub_tab_name
											from
												1 for length (tabname)
										)
									)
								) then
									st_time := substring (
										sub_tab_name
										from
											length (tabname) + 2 for length (sub_tab_name)
									) ; st_time := substring (st_time from 1 for 4) || '-' || substring (st_time from 5 for 6) ; sql_desc := 'create or replace rule insert_' || sub_tab_name || ' as on insert to ' || tabname || ' where new.' || timefield || ' >= ''' || substring (
										to_char(
											to_timestamp(st_time,'yyyy-mm-dd'),'yyyy-mm-dd'
										)
										from
											1 for 10
									) || '''::date and new.' || timefield || ' <''' || substring (
										to_char(
											to_timestamp(st_time,'yyyy-mm-dd') + interval '1 month','yyyy-mm-dd'
										)
										from
											1 for 10
									) || '''::date do instead insert into ' || sub_tab_name || '(' ; value_desc := 'values (' ; open fetch_sub_column_refcursor ; loop fetch fetch_sub_column_refcursor into column_name_desc ;
								if found then
									sql_desc := sql_desc || column_name_desc || ',' ; value_desc := value_desc || 'new.' || column_name_desc || ',' ;
								else
									exit ;
								end
								if ;
								end loop ; sql_desc := substring (
									sql_desc
									from
										1 for length (sql_desc) - 1
								) || ')' ; value_desc := substring (
									value_desc
									from
										1 for length (value_desc) - 1
								) || ');' ; all_sql_desc := sql_desc || value_desc ;  execute all_sql_desc ; close fetch_sub_column_refcursor ;
							else
 
							end
							if ;
							else
 
							end
							if ;
							else 
								exit ;
							end
							if ;
							end loop ; close fetch_sub_tab_refcursor ;  return fetch_sub_tab_refcursor ; exception
							when others then
								raise exception 'error--(%)',sqlerrm ;
							end ; $body$ language plpgsql;
 
--------调用方式----有两个参数，第一个是主表名，第二个是根据哪个字段进行分表------  
begin
;
 
select
	cursor_demo (
		'your_table_name','your_field'
	);
 
commit;