磨砺技术珠矶,践行数据之道,追求卓越价值
回到上一级页面:PostgreSQL基础知识与基本操作索引页 回到*页面:PostgreSQL索引页
[作者 高健@博客园 luckyjackgao@gmail.com]
由于数据少,执行计划中没有使用Index Scan
postgres=# CREATE TABLE items (
postgres(# itemid serial NOT NULL PRIMARY KEY,
postgres(# itemname text NOT NULL,
postgres(# tags hstore);
NOTICE: CREATE TABLE will create implicit sequence "items_itemid_seq" for serial column "items.itemid"
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "items_pkey" for table "items"
CREATE TABLE
postgres=#
postgres=# INSERT INTO items (itemname, tags) VALUES ('item1', 'color => red, category => stuff');
INSERT 0 1
postgres=#
postgres=# INSERT INTO items (itemname, tags) VALUES ('item2', 'color => green, category => manager');
INSERT 0 1
postgres=#
postgres=# CREATE INDEX hstoreidx ON items USING gist(tags);
CREATE INDEX
postgres=#
postgres=# SELECT itemname FROM items WHERE tags @> 'color=>red';
itemname
----------
item1
(1 row)
postgres=# SELECT itemname FROM items WHERE tags @> 'color=>green';
itemname
----------
item2
(1 row)
postgres=# SELECT itemname FROM items WHERE tags @> 'color=>blue';
itemname
----------
(0 rows)
postgres=# EXPLAIN SELECT itemname FROM items WHERE tags @> 'color=>red';
QUERY PLAN
------------------------------------------------------
Seq Scan on items (cost=0.00..1.02 rows=1 width=32)
Filter: (tags @> '"color"=>"red"'::hstore)
(2 rows)
postgres=#
postgres=# SELECT itemname FROM items WHERE tags ? 'color';
itemname
----------
item1
item2
(2 rows)
postgres=# EXPLAIN SELECT itemname FROM items WHERE tags ? 'color';
QUERY PLAN
------------------------------------------------------
Seq Scan on items (cost=0.00..1.02 rows=1 width=32)
Filter: (tags ? 'color'::text)
(2 rows)
postgres=#
本文转自健哥的数据花园博客园博客,原文链接:http://www.cnblogs.com/gaojian/p/3351469.html,如需转载请自行联系原作者