Question

我有一张像这样安静的桌子：

CREATE TABLE myTable (
    family text,
    names text[]
)

我可以这样搜索：

SELECT family
FROM myTable where names @> array['B0WP04'];

但我想这样做：

SELECT family
FROM myTable where names @> array['%P0%'];

这可能吗？

Answer 1

您可以使用parray_gin扩展程序https://github.com/theirix/parray_gin

据说这个扩展只能达到9.2，但我只是在9.3上安装并测试它，效果很好。

以下是如何在类似ubuntu的系统上安装它：）

# install postgresql extension network client and postgresql extension build tools
sudo apt-get install python-setuptools
easy_install pgxnclient
sudo apt-get install postgresql-server-dev-9.3

# get the extension
pgxn install parray_gin

这是我的测试

-- as a superuser: add the extension to the current database
CREATE EXTENSION parray_gin;

-- as a normal user
CREATE TABLE test (
  id    SERIAL PRIMARY KEY,
  names TEXT []
);

INSERT INTO test (names) VALUES
  (ARRAY ['nam1', 'nam2']),
  (ARRAY ['2nam1', '2nam2']),
  (ARRAY ['Hello', 'Woooorld']),
  (ARRAY ['Woooorld', 'Hello']),
  (ARRAY [] :: TEXT []),
  (NULL),
  (ARRAY ['Hello', 'is', 'it', 'me', 'you''re', 'looking', 'for', '?']);

-- double up the rows in test table, with many rows, the index is used
INSERT INTO test (names) (SELECT names FROM test);

SELECT count(*) from test; /*
 count  
--------
 997376
(1 row)
*/

现在我们有一些测试数据，这是神奇的时间：

-- http://pgxn.org/dist/parray_gin/doc/parray_gin.html
CREATE INDEX names_idx ON test USING GIN (names parray_gin_ops);

--- now it's time for some tests
EXPLAIN ANALYZE SELECT * FROM test WHERE names @> ARRAY ['is']; /*

-- WITHOUT INDEX ON NAMES
                                                 QUERY PLAN                                                 
------------------------------------------------------------------------------------------------------------
 Seq Scan on test  (cost=0.00..25667.00 rows=1138 width=49) (actual time=0.021..508.599 rows=51200 loops=1)
   Filter: (names @> '{is}'::text[])
   Rows Removed by Filter: 946176
 Total runtime: 653.879 ms
(4 rows)

-- WITH INDEX ON NAMES
                                                         QUERY PLAN                                                         
----------------------------------------------------------------------------------------------------------------------------
 Bitmap Heap Scan on test  (cost=455.73..3463.37 rows=997 width=49) (actual time=14.327..240.365 rows=51200 loops=1)
   Recheck Cond: (names @> '{is}'::text[])
   ->  Bitmap Index Scan on names_idx  (cost=0.00..455.48 rows=997 width=0) (actual time=12.241..12.241 rows=51200 loops=1)
         Index Cond: (names @> '{is}'::text[])
 Total runtime: 341.750 ms
(5 rows)

*/

EXPLAIN ANALYZE SELECT * FROM test WHERE names @@> ARRAY ['%nam%']; /*

-- WITHOUT INDEX ON NAMES
                                                 QUERY PLAN                                                 
------------------------------------------------------------------------------------------------------------
 Seq Scan on test  (cost=0.00..23914.20 rows=997 width=49) (actual time=0.023..590.093 rows=102400 loops=1)
   Filter: (names @@> '{%nam%}'::text[])
   Rows Removed by Filter: 894976
 Total runtime: 796.636 ms
(4 rows)

-- WITH INDEX ON NAMES
                                                         QUERY PLAN                                                          
-----------------------------------------------------------------------------------------------------------------------------
 Bitmap Heap Scan on test  (cost=159.73..3167.37 rows=997 width=49) (actual time=20.164..293.942 rows=102400 loops=1)
   Recheck Cond: (names @@> '{%nam%}'::text[])
   ->  Bitmap Index Scan on names_idx  (cost=0.00..159.48 rows=997 width=0) (actual time=18.539..18.539 rows=102400 loops=1)
         Index Cond: (names @@> '{%nam%}'::text[])
 Total runtime: 490.060 ms
(5 rows)

*/

最终的性能完全取决于您的数据和查询，但在我的虚拟示例中，此扩展非常有效地将查询时间缩短了一半。

Answer 2

在Radek的回答中添加一点，我试过

select family
from myTable where 
exists (select 1 from unnest(names) as name where name like '%P0%');

它也有效。我在PostgreSQL文档中搜索un()函数，但无法找到任何内容。

我并不是说它没有做任何事情，但我只是好奇un()函数应该做什么（并且很高兴我的问题得到解决）

Answer 3

在postgreSQL 9.3中，您可以：

boolean

但请记住，它可能会产生重复，因此您需要添加不同的影响。

对于早期版本：

select family
from myTable 
join lateral unnest(mytable.names) as un(name) on true
where un.name like '%P0%';

有没有办法在PostgreSQL中的多值字段中搜索部分匹配？

3 个答案: