Postgres2015全國用戶大會將於11月20至21日在北京麗亭華苑酒店召開。本次大會嘉賓陣容強大，國內頂級PostgreSQL數據庫專家將悉數到場，並特邀歐洲、俄羅斯、日本、美國等國家和地區的數據庫方面專家助陣:
- Postgres-XC項目的發起人鈴木市一(SUZUKI Koichi)
- Postgres-XL的項目發起人Mason Sharp
- pgpool的作者石井達夫(Tatsuo Ishii)
- PG-Strom的作者海外浩平(Kaigai Kohei)
- Greenplum研發總監姚延棟
- 周正中(德哥), PostgreSQL中國用戶會創始人之一
- 汪洋，平安科技數據庫技術部經理
- ……
| 2015年度PG大象會報名地址：http://postgres2015.eventdove.com/PostgreSQL中國社區： http://postgres.cn/PostgreSQL專業1羣： 3336901（已滿）PostgreSQL專業2羣： 100910388PostgreSQL專業3羣： 150657323 |
 |
其中index-by table是不限元素個數，支持字符串或INT下標。
用法舉例：DECLARE
-- Associative array indexed by string:
TYPE population IS TABLE OF NUMBER -- Associative array type
INDEX BY VARCHAR2(64); -- indexed by string
city_population population; -- Associative array variable
i VARCHAR2(64); -- Scalar variable
BEGIN
-- Add elements (key-value pairs) to associative array:
city_population('Smallville') := 2000;
city_population('Midland') := 750000;
city_population('Megalopolis') := 1000000;
-- Change value associated with key 'Smallville':
city_population('Smallville') := 2001;
-- Print associative array:
i := city_population.FIRST; -- Get first element of array
WHILE i IS NOT NULL LOOP
DBMS_Output.PUT_LINE
('Population of ' || i || ' is ' || city_population(i));
i := city_population.NEXT(i); -- Get next element of array
END LOOP;
END;
/
Result:
Population of Megalopolis is 1000000
Population of Midland is 750000
Population of Smallville is 2001
Example 5-2 defines a type of associative array indexed by PLS_INTEGER and a function that returns an associative array of that type.
Example 5-2 Function Returns Associative Array Indexed by PLS_INTEGER
DECLARE
TYPE sum_multiples IS TABLE OF PLS_INTEGER INDEX BY PLS_INTEGER;
n PLS_INTEGER := 5; -- number of multiples to sum for display
sn PLS_INTEGER := 10; -- number of multiples to sum
m PLS_INTEGER := 3; -- multiple
FUNCTION get_sum_multiples (
multiple IN PLS_INTEGER,
num IN PLS_INTEGER
) RETURN sum_multiples
IS
s sum_multiples;
BEGIN
FOR i IN 1..num LOOP
s(i) := multiple * ((i * (i + 1)) / 2); -- sum of multiples
END LOOP;
RETURN s;
END get_sum_multiples;
BEGIN
DBMS_OUTPUT.PUT_LINE (
'Sum of the first ' || TO_CHAR(n) || ' multiples of ' ||
TO_CHAR(m) || ' is ' || TO_CHAR(get_sum_multiples (m, sn)(n))
);
END;
/
Result:
Sum of the first 5 multiples of 3 is 45
在PostgreSQL plpgsql函數中對應的用法：
PostgreSQL中不需要指定數組長度，可以存儲任意個元素。
但是不能使用字符串下標。
postgres=# create table t1(id int,info text);
CREATE TABLE
postgres=# do language plpgsql $$
declare
v _t1; -- _t1表示t1表的數組類型
v1 t1;
begin
v1.id := 10;
v1.info := 'abc';
v[1] := v1;
v[2] := '(11,"hello")';
v1.id := 100;
v1.info := 'i am digoal';
v[3] := v1;
foreach v1 in array v loop
raise notice '%, %, %', v1, v1.id, v1.info;
end loop;
end;
$$;
NOTICE: 00000: (10,abc), 10, abc
LOCATION: exec_stmt_raise, pl_exec.c:3074
NOTICE: 00000: (11,hello), 11, hello
LOCATION: exec_stmt_raise, pl_exec.c:3074
NOTICE: 00000: (100,"i am digoal"), 100, i am digoal
LOCATION: exec_stmt_raise, pl_exec.c:3074
DO
如果要存儲非結構化數據，可以使用jsonb或者hstore和數組的組合。
不過目前在plpgsql中只能對非結構化數據一次性賦值，不能部分賦值。例如：
postgres=# do language plpgsql $$
declare
v1 hstore := '';
ky text;
begin
v1 := v1 || '"a"=>1'::hstore;
v1 := v1 || hstore('b', '2'); -- 另一種hstore value寫法
v1 := v1 || '"b"=>100'::hstore; -- 覆蓋或修改b的值
foreach ky in array akeys(v1) loop
raise notice '%, %', ky, v1->ky; -- hstore->key 獲取指定key的value
end loop;
end;
$$;
NOTICE: 00000: a, 1
LOCATION: exec_stmt_raise, pl_exec.c:3074
NOTICE: 00000: b, 100
LOCATION: exec_stmt_raise, pl_exec.c:3074
DO
LOCATION: exec_stmt_raise, pl_exec.c:3074
NOTICE: 00000: b, 100
LOCATION: exec_stmt_raise, pl_exec.c:3074
DO