postgreSQL | ltree

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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。

  • @H_301_43@

    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
    • @H_301_43@
      • 查询:与刘德华同一个区域(港台,男歌手)的歌手
      • @H_301_43@

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