postgreSQL | ltree

参考链接

树状数据存储与查询(非递归) - Use ltree extension deal tree-like data type（德哥github博文）

postgresql ltree类型（推酷）

ltree的官方介绍

1. 安装、数据类型介绍、操作符介绍、函数介绍

安装 "ltree" 索引扩展(使用超级用户)

create extension ltree;

查看

select * from pg_extension ;
\dT

数据类型介绍

• ltree (目前只支持A-Z,a-z,0-9,_作为label的合法字符)

  树形结构类型,一个ltree被称为一个path,由1或多个LABEL组成,每个label由A-Za-z0-9_组成。ltree是由标签和分隔符组成的字符串，比如：L1.L2.L3

• lquery

  规则表达式,用于匹配ltree类型.

  具体参考手册,需要注意的是%匹配的不是一个label,而是label里的一个单词(_为单词分隔符

• ltxtquery

  一般用于全文扫描，注意，只有ltxtquery类型是符号和匹配的内容是可以有空格隔开的,lquery和ltree不支持空格。

操作符介绍:

Operator	Returns	Description
ltree @> ltree	boolean	is left argument an ancestor of right (or equal)?
ltree <@ ltree	boolean	is left argument a descendant of right (or equal)?
ltree ~ lquery	boolean	does ltree match lquery?
lquery ~ ltree	boolean	does ltree match lquery?
ltree ? lquery[]	boolean	does ltree match any lquery in array?
lquery[] ? ltree	boolean	does ltree match any lquery in array?
ltree @ ltxtquery	boolean	does ltree match ltxtquery?
ltxtquery @ ltree	boolean	does ltree match ltxtquery?
ltree || ltree	ltree	concatenate ltree paths
ltree || text	ltree	convert text to ltree and concatenate
text || ltree	ltree	convert text to ltree and concatenate
ltree[] @> ltree	boolean	does array contain an ancestor of ltree?
ltree <@ ltree[]	boolean	does array contain an ancestor of ltree?
ltree[] <@ ltree	boolean	does array contain a descendant of ltree?
ltree @> ltree[]	boolean	does array contain a descendant of ltree?
ltree[] ~ lquery	boolean	does array contain any path matching lquery?
lquery ~ ltree[]	boolean	does array contain any path matching lquery?
ltree[] ? lquery[]	boolean	does ltree array contain any path matching any lquery?
lquery[] ? ltree[]	boolean	does ltree array contain any path matching any lquery?
ltree[] @ ltxtquery	boolean	does array contain any path matching ltxtquery?
ltxtquery @ ltree[]	boolean	does array contain any path matching ltxtquery?
ltree[] ?@> ltree	ltree	first array entry that is an ancestor of ltree; NULL if none
ltree[] ?<@ ltree	ltree	first array entry that is a descendant of ltree; NULL if none
ltree[] ?~ lquery	ltree	first array entry that matches lquery; NULL if none
ltree[] ?@ ltxtquery	ltree	first array entry that matches ltxtquery; NULL if none

函数简单介绍:

Function	Return Type	Description	Example	Result
subltree(ltree,int start,int end)	ltree	subpath of ltree from position start to position end-1 (counting from 0)	subltree('Top.Child1.Child2',1,2)	Child1
subpath(ltree,int offset,int len)	ltree	subpath of ltree starting at position offset,length len. If offset is negative,subpath starts that far from the end of the path. If len is negative,leaves that many labels off the end of the path.	subpath('Top.Child1.Child2',2)	Top.Child1
subpath(ltree,int offset)	ltree	subpath of ltree starting at position offset,extending to end of path. If offset is negative,subpath starts that far from the end of the path.	subpath('Top.Child1.Child2',1)	Child1.Child2
nlevel(ltree)	integer	number of labels in path	nlevel('Top.Child1.Child2')	3
index(ltree a,ltree b)	integer	position of first occurrence of b in a; -1 if not found	index('0.1.2.3.5.4.5.6.8.5.6.8','5.6')	6
index(ltree a,ltree b,int offset)	integer	position of first occurrence of b in a,searching starting at offset; negative offsetmeans start -offset labels from the end of the path	index('0.1.2.3.5.4.5.6.8.5.6.8','5.6',-4)	9
text2ltree(text)	ltree	cast text to ltree	-	-
ltree2text(ltree)	text	cast ltree to text	-	-
lca(ltree,ltree,...)	ltree	lowest common ancestor,i.e.,longest common prefix of paths (up to 8 arguments supported)	lca('1.2.2.3','1.2.3.4.5.6')	1.2
lca(ltree[])	ltree	lowest common ancestor,longest common prefix of paths	lca(array['1.2.2.3'::ltree,'1.2.3'])	1.2

2. 样例

2.1 推酷、德哥博客都用到的

建表

create table public.test(
id serial,song ltree not null);

初始化后的数据

• 查询：刘德华的歌曲

• 查询：与刘德华同一个区域（港台，男歌手）的歌手