PostgreSQL 建立分割槽表，SQL優化之PostgreSQL Table Partitioning

PostgreSQL中使用動態SQL-實現自動按時間建立表分割槽

declare
createOn varchar(32);
createYY varchar(4);
tableName VARCHAR(48);
isExist int;
r record;
sqlStr text;
sqlDel text;
sqlIn text;
begin

//通過以下語句給createOn變數賦值
select start_time into createOn from tech_trial_t where start_time <>'' order by start_time asc limit 1;
createYY := substr(createOn, 1,4);

select count(*) into isExist from pg_class where relname = 'tech_trial_t_y' || createYY;

if (isExist=0) then
sqlStr='create table if not exists tech_trial_t_y' || createYY || ' (like tech_trial_t_y2017 including indexes);'; 
execute sqlStr;
end if;
	
sqlStr := 'select relname from pg_class where relname like ''tech_trial_t_y20%'' and relname not like ''%_idx'';';  
 //必須排除索引，因為relname 是表格，索引，檢視等的名稱

//for 語句迴圈取值賦值
for r in execute sqlStr loop
 sqlDel := 'truncate table ' || r.relname;     
	EXECUTE sqlDel;
//直接寫 truncate table r.relname; 不能執行，貌似不能知道r.relname是什麼東東。
所以寫成字串語句執行字串語句。


 sqlIn := 'insert into ' || r.relname || ' select * from tech_trial_t_view_year tv where tv.start_time >= substr( ''' ||r.relname || ''',15,4) ||''-01-01 00:00:00'' and tv.start_time <= substr('''|| r.relname ||''',15,4) ||''-12-31 23:59:59'';';
EXECUTE sqlIn;
end loop;
return NULL;
end
 

DECLARE start_text TEXT;
DECLARE insert_statement TEXT;
BEGIN
	start_text := substr(NEW.start_time, 1 ,4);	
	insert_statement := 'INSERT INTO tech_trial_t_'
		|| start_text
		||' VALUES ($1.*)';
	EXECUTE insert_statement USING NEW;
	RETURN NULL;
	EXCEPTION
	WHEN UNDEFINED_TABLE
	THEN
		EXECUTE
			'CREATE TABLE IF NOT EXISTS tech_trial_t_'
			|| start_text
			|| '(CHECK (start_time >= '''
			|| start_text
			|| '-01-01 00:00:00'' and start_time < ''' || start_text || '-12-31 23:59:59'')) INHERITS (tech_trial_t_year)';
		RAISE NOTICE 'CREATE NON-EXISTANT TABLE tech_trial_t_year_%', start_text;
		EXECUTE
			'CREATE INDEX tech_trial_t_key_'
			|| start_text
			|| ' ON tech_trial_t_'
			|| start_text
			|| '(start_time)';
		EXECUTE insert_statement USING NEW;
    RETURN NULL;
END;

//必須保證每條插入的start_time(分割槽關鍵字）非空。
NEW表示新插入的記錄