postgreSQL | ltree

參考連接

樹狀數據存儲與查詢(非遞歸) - Use ltree extension deal tree-like data type（德哥github博文）

postgresql ltree類型（推酷）

ltree的官方介紹 

1. 安裝、數據類型介紹、操做符介紹、函數介紹 

安裝  "ltree" 索引擴展(使用超級用戶)

create extension ltree;

查看

select * from pg_extension ;
\dT

數據類型介紹

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

  樹形結構類型,一個ltree被稱爲一個path,由1或多個LABEL組成,每一個label由A-Za-z0-9_組成。ltree是由標籤和分隔符組成的字符串，好比：L1.L2.L3

•  lquery

  規則表達式,用於匹配ltree類型.

  具體參考手冊,須要注意的是%匹配的不是一個label,而是label裏的一個單詞(_爲單詞分隔符

•  ltxtquery

  通常用於全文掃描，注意，只有ltxtquery類型是符號和匹配的內容是能夠有空格隔開的,lquery和ltree不支持空格。

操做符介紹:

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

函數簡單介紹:

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',0,2)	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, i.e., longest common prefix of paths	lca(array['1.2.2.3'::ltree,'1.2.3'])	1.2

2. 樣例

2.1 推酷、德哥博客都用到的

建表

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

初始化後的數據

• 查詢：劉德華的歌曲

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