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@ -15,7 +15,7 @@ |
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<sect2> |
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<title>Definitions</title> |
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<para> |
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A <emphasis>label</emphasis> of a node is a sequence of one or more words |
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A <firstterm>label</firstterm> of a node is a sequence of one or more words |
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separated by blank character '_' and containing letters and digits ( for |
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example, [a-zA-Z0-9] for C locale). The length of a label is limited by 256 |
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bytes. |
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@ -24,9 +24,9 @@ |
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Example: 'Countries', 'Personal_Services' |
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</para> |
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<para> |
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A <emphasis>label path</emphasis> of a node is a sequence of one or more |
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A <firstterm>label path</firstterm> of a node is a sequence of one or more |
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dot-separated labels l1.l2...ln, represents path from root to the node. The |
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length of a label path is limited by 65Kb, but size <= 2Kb is preferrable. |
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length of a label path is limited by 65Kb, but size <= 2Kb is preferrable. |
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We consider it's not a strict limitation (maximal size of label path for |
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DMOZ catalogue - <ulink url="http://www.dmoz.org"></ulink>, is about 240 |
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bytes!) |
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@ -85,7 +85,7 @@ |
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</listitem> |
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<listitem> |
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<para>% Don't account word separator '_' in label matching, that is |
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'Russian%' would match 'Russian_nations', but not 'Russian' |
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'Russian%' would match 'Russian_nations', but not 'Russian' |
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</para> |
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</listitem> |
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</itemizedlist> |
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@ -143,7 +143,7 @@ |
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the end of word. The meaning of modifiers are the same as for lquery. |
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</para> |
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<para> |
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Example: <literal>'Europe & Russia*@ & !Transportation'</literal> |
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Example: <literal>'Europe & Russia*@ & !Transportation'</literal> |
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</para> |
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<para> |
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Search paths contain words 'Europe' and 'Russia*' (case-insensitive) and |
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@ -164,21 +164,21 @@ |
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<itemizedlist> |
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<listitem> |
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<para> |
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<literal><,>,<=,>=,=, <></literal> |
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<literal><,>,<=,>=,=, <></literal> |
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- Have their usual meanings. Comparison is doing in the order of direct |
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tree traversing, children of a node are sorted lexicographic. |
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</para> |
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</listitem> |
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<listitem> |
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<para> |
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<literal>ltree @> ltree</literal> |
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<literal>ltree @> ltree</literal> |
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- returns TRUE if left argument is an ancestor of right argument (or |
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equal). |
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</para> |
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</listitem> |
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<listitem> |
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<para> |
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<literal>ltree <@ ltree </literal> |
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<literal>ltree <@ ltree </literal> |
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- returns TRUE if left argument is a descendant of right argument (or |
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equal). |
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</para> |
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@ -216,13 +216,13 @@ |
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<itemizedlist> |
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<listitem> |
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<para> |
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<literal>ltree[] @> ltree, ltree <@ ltree[]</literal> |
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<literal>ltree[] @> ltree, ltree <@ ltree[]</literal> |
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- returns TRUE if array ltree[] contains an ancestor of ltree. |
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</para> |
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</listitem> |
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<listitem> |
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<para> |
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<literal>ltree @> ltree[], ltree[] <@ ltree</literal> |
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<literal>ltree @> ltree[], ltree[] <@ ltree</literal> |
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- returns TRUE if array ltree[] contains a descendant of ltree. |
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</para> |
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</listitem> |
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@ -248,7 +248,7 @@ |
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</listitem> |
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<listitem> |
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<para> |
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<literal>ltree[] ?@> ltree, ltree ?<@ ltree[], ltree[] ?~ lquery, ltree[] ?@ ltxtquery</literal> |
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<literal>ltree[] ?@> ltree, ltree ?<@ ltree[], ltree[] ?~ lquery, ltree[] ?@ ltxtquery</literal> |
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- returns first element of array ltree[] satisfies corresponding condition |
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and NULL in vice versa. |
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@ -292,7 +292,7 @@ |
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</listitem> |
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<listitem> |
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<para>GiST index over ltree[]: |
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<literal>ltree[]<@ ltree, ltree @> ltree[], @, ~, ?.</literal> |
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<literal>ltree[]<@ ltree, ltree @> ltree[], @, ~, ?.</literal> |
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</para> |
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<para> |
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Example: |
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@ -418,8 +418,8 @@ |
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<title>Example</title> |
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<programlisting> |
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createdb ltreetest |
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psql ltreetest < /usr/local/pgsql/share/contrib/ltree.sql |
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psql ltreetest < ltreetest.sql |
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psql ltreetest < /usr/local/pgsql/share/contrib/ltree.sql |
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psql ltreetest < ltreetest.sql |
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</programlisting> |
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<para> |
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@ -445,7 +445,7 @@ shown below: |
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</para> |
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<programlisting> |
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ltreetest=# select path from test where path <@ 'Top.Science'; |
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ltreetest=# select path from test where path <@ 'Top.Science'; |
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path |
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------------------------------------ |
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Top.Science |
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@ -481,7 +481,7 @@ ltreetest=# select path from test where path ~ '*.!pictures@.*.Astronomy.*'; |
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Full text search: |
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</para> |
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<programlisting> |
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ltreetest=# select path from test where path @ 'Astro*% & !pictures@'; |
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ltreetest=# select path from test where path @ 'Astro*% & !pictures@'; |
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path |
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------------------------------------ |
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Top.Science.Astronomy |
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@ -490,7 +490,7 @@ ltreetest=# select path from test where path @ 'Astro*% & !pictures@'; |
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Top.Hobbies.Amateurs_Astronomy |
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(4 rows) |
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ltreetest=# select path from test where path @ 'Astro* & !pictures@'; |
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ltreetest=# select path from test where path @ 'Astro* & !pictures@'; |
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path |
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------------------------------------ |
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Top.Science.Astronomy |
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@ -502,7 +502,7 @@ ltreetest=# select path from test where path @ 'Astro* & !pictures@'; |
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Using Functions: |
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</para> |
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<programlisting> |
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ltreetest=# select subpath(path,0,2)||'Space'||subpath(path,2) from test where path <@ 'Top.Science.Astronomy'; |
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ltreetest=# select subpath(path,0,2)||'Space'||subpath(path,2) from test where path <@ 'Top.Science.Astronomy'; |
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?column? |
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------------------------------------------ |
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Top.Science.Space.Astronomy |
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@ -519,7 +519,7 @@ LANGUAGE SQL IMMUTABLE; |
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</para> |
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<programlisting> |
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ltreetest=# select ins_label(path,2,'Space') from test where path <@ 'Top.Science.Astronomy'; |
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ltreetest=# select ins_label(path,2,'Space') from test where path <@ 'Top.Science.Astronomy'; |
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ins_label |
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------------------------------------------ |
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Top.Science.Space.Astronomy |
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@ -537,7 +537,7 @@ CREATE FUNCTION ins_label(ltree, ltree, text) RETURNS ltree |
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AS 'select subpath($1,0,nlevel($2)) || $3 || subpath($1,nlevel($2));' |
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LANGUAGE SQL IMMUTABLE; |
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ltreetest=# select ins_label(path,'Top.Science'::ltree,'Space') from test where path <@ 'Top.Science.Astronomy'; |
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ltreetest=# select ins_label(path,'Top.Science'::ltree,'Space') from test where path <@ 'Top.Science.Astronomy'; |
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ins_label |
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------------------------------------------ |
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Top.Science.Space.Astronomy |
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@ -606,7 +606,7 @@ ltreetest=# select ins_label(path,'Top.Science'::ltree,'Space') from test where |
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Q2: The same as Q1 but with counting of successors |
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</para> |
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<programlisting> |
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select path as parentpath , (select count(*)-1 from dmoz where path <@ |
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select path as parentpath , (select count(*)-1 from dmoz where path <@ |
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p.path) as count from dmoz p where path ~ 'Top.Adult.Arts.Animation.*{1}'; |
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parentpath | count |
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-----------------------------------+------- |
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@ -620,7 +620,7 @@ ltreetest=# select ins_label(path,'Top.Science'::ltree,'Space') from test where |
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Q3: Get all parents |
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</para> |
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<programlisting> |
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select path from dmoz where path @> 'Top.Adult.Arts.Animation' order by |
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select path from dmoz where path @> 'Top.Adult.Arts.Animation' order by |
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path asc; |
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path |
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-------------------------- |
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@ -636,8 +636,8 @@ ltreetest=# select ins_label(path,'Top.Science'::ltree,'Space') from test where |
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Q4: Get all parents with counting of children |
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</para> |
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<programlisting> |
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select path, (select count(*)-1 from dmoz where path <@ p.path) as count |
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from dmoz p where path @> 'Top.Adult.Arts.Animation' order by path asc; |
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select path, (select count(*)-1 from dmoz where path <@ p.path) as count |
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from dmoz p where path @> 'Top.Adult.Arts.Animation' order by path asc; |
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path | count |
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--------------------------+-------- |
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Top | 300273 |
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@ -753,7 +753,7 @@ ltreetest=# select ins_label(path,'Top.Science'::ltree,'Space') from test where |
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<para> |
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For ltree we store LPS in a B-tree, implemented using GiST. Each node entry is |
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represented by (left_bound, signature, right_bound), so that we could speedup |
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operations <literal><, <=, =, >=, ></literal> using left_bound, right_bound and prune branches of |
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operations <literal><, <=, =, >=, ></literal> using left_bound, right_bound and prune branches of |
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a tree using signature. |
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</para> |
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</sect2> |
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@ -768,4 +768,3 @@ ltreetest=# select ins_label(path,'Top.Science'::ltree,'Space') from test where |
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</para> |
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</sect2> |
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</sect1> |
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Tom Lane
19 years ago