最近在PostgreSQL的Mail List中參與討論了一個問題： ANALYZE'ing table hierarchies。

網友認為在Analyze分區表的時候，只能看到主表的analyze日期更新到最新，但是子表的日期沒有變化，他認為analyze應該是在分析主表的時候會將與之相關的子表一起更新。

為此測試了一下，發現無論主表還是子表，需要單獨的對其進行analyze才可以更新其最新的統計信息。

以下是實驗部分：

music=> create table music(id int,name text,style text);

CREATE TABLE

music=> create table rock (check(style = 'rock')) inherits(music);

CREATE TABLE

music=> create table pop (check(style = 'pop')) inherits(music);

CREATE TABLE

music=> create table classic (check(style = 'classic')) inherits(music);

CREATE TABLE

music=> ?create table jazz (check(style = 'jazz')) inherits(music);

CREATE TABLE

music=> \dS+ music

Table "eric.music"

Column | ?Type ? | Modifiers | Storage ?| Stats target | Description

--------+---------+-----------+----------+--------------+-------------

id ? ? | integer | ? ? ? ? ? | plain ? ?| ? ? ? ? ? ? ?|

name ? | text ? ?| ? ? ? ? ? | extended | ? ? ? ? ? ? ?|

style ?| text ? ?| ? ? ? ? ? | extended | ? ? ? ? ? ? ?|

Child tables: classic,

jazz,

pop,

rock

music=> create index music_pop_id on pop (id);

CREATE INDEX

music=> ?create index music_rock_id on rock (id);

CREATE INDEX

music=> create index music_jazz_id on jazz (id);

CREATE INDEX

music=> create index music_classic_id on classic (id);

CREATE INDEX

music=> ?CREATE OR REPLACE FUNCTION music_insert_trigger()

music-> ?RETURNS TRIGGER AS

music-> ?$$

music$> ?BEGIN

music$> ? ? ? IF (NEW.style = 'rock') THEN

music$> ? ? ? ? ? INSERT INTO rock VALUES (NEW.*);

music$> ? ? ? ELSEIF (NEW.style = 'pop') THEN

music$> ? ? ? ? ? INSERT INTO pop VALUES (NEW.*);

music$> ? ? ? ELSEIF (NEW.style = 'pop') THEN

music$> ? ? ? ? ? INSERT INTO pop VALUES (NEW.*);

music$> ? ? ? ELSEIF (NEW.style = 'jazz') THEN

music$> ? ? ? ? ? INSERT INTO jazz VALUES (NEW.*);

music$> ? ? ? ELSEIF (NEW.style = 'classic') THEN

music$> ? ? ? ? ? INSERT INTO classic VALUES (NEW.*);

music$> ? ? ? END IF;

music$> ? ? ? RETURN NULL;

music$> ?END;

music$> ?$$

music-> ?LANGUAGE plpgsql ;

CREATE FUNCTION

music=> CREATE TRIGGER insert_music_trigger

music-> BEFORE INSERT ON ?music

music-> FOR EACH row EXECUTE PROCEDURE music_insert_trigger() ;

CREATE TRIGGER

music=> insert into music values(2,'Have a Nice Day','pop');

INSERT 0 0

music=> insert into music values(1,'21 Gun','rock');

INSERT 0 0

music=> select * from music;

id | ? ? ?name ? ? ? | style

----+-----------------+-------

1 | 21 Gun ? ? ? ? ?| rock

2 | Have a Nice Day | pop

(2 rows)

music=> select * from pop;

id | ? ? ?name ? ? ? | style

----+-----------------+-------

2 | Have a Nice Day | pop

(1 row)

music=> select * from rock;

id | ?name ?| style

----+--------+-------

1 | 21 Gun | rock

(1 row)

music=> analyze verbose music ;

INFO: ?analyzing "eric.music"

INFO: ?"music": scanned 0 of 0 pages, containing 0 live rows and 0 dead rows; 0 rows in sample, 0 estimated total rows

INFO: ?analyzing "eric.music" inheritance tree

INFO: ?"rock": scanned 1 of 1 pages, containing 1 live rows and 0 dead rows; 1 rows in sample, 1 estimated total rows

INFO: ?"pop": scanned 1 of 1 pages, containing 1 live rows and 0 dead rows; 1 rows in sample, 1 estimated total rows

ANALYZE

music=> select relname, last_analyze from pg_stat_user_tables where relname = 'music';

relname | ? ? ? ? last_analyze

---------+-------------------------------

music ? | 2016-02-18 22:29:56.528758-08

(1 row)

music=> select relname, last_analyze from pg_stat_user_tables where relname = 'pop';

relname | last_analyze

---------+--------------

pop ? ? |

(1 row)

music=> select relname, last_analyze from pg_stat_user_tables where relname = 'rock';

relname | last_analyze

---------+--------------

rock ? ?|

(1 row)

music=> analyze verbose pop;

INFO: ?analyzing "eric.pop"

INFO: ?"pop": scanned 1 of 1 pages, containing 1 live rows and 0 dead rows; 1 rows in sample, 1 estimated total rows

ANALYZE

music=> select relname, last_analyze from pg_stat_user_tables where relname = 'rock';

relname | last_analyze

---------+--------------

rock ? ?|

(1 row)

music=> select relname, last_analyze from pg_stat_user_tables where relname = 'pop';

relname | ? ? ? ? last_analyze

---------+-------------------------------

pop ? ? | 2016-02-18 22:31:55.666556-08

(1 row)

music=> analyze verbose rock;

INFO: ?analyzing "eric.rock"

INFO: ?"rock": scanned 1 of 1 pages, containing 1 live rows and 0 dead rows; 1 rows in sample, 1 estimated total rows

ANALYZE

music=> select relname, last_analyze from pg_stat_user_tables where relname = 'rock';

relname | ? ? ? ? last_analyze

---------+-------------------------------

rock ? ?| 2016-02-18 22:34:16.526558-08

(1 row)

總結

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