PostgreSQL建表动作分析
首先，建立表：
pgsql=# create table tab10(id integer); CREATE TABLE pgsql=# select 147525::regclass; regclass ---------- tab10 (1 row) pgsql=#
查看此时的文件信息：
[pgsql@localhost 16384]$ pwd /home/pgsql/DemoDir/base/16384[pgsql@localhost 16384]$ ls -l 147525 -rw------- 1 pgsql pgsql 0 Jul 4 13:45 147525 [pgsql@localhost 16384]$
此时，文件刚刚建立好，还是一个空文件
同时，可以看到，因为建立了一个表，所以数据字典中有很多系统表被更新：
例如：pg_type。
这个确实有点超乎想象，因为我并未增加任何的新type。
pgsql=# select count(*) from pg_type; count ------- 313 (1 row) pgsql=# create table tab10(id integer); CREATE TABLE pgsql=# select count(*) from pg_type; count ------- 315 (1 row)
看看增加了什么：
pgsql=# \x Expanded display is on. pgsql=# select * from pg_type where typname='tab10'; -[ RECORD 1 ]--+------------ typname | tab10 typnamespace | 2200 typowner | 10 typlen | -1 typbyval | f typtype | c typcategory | C typispreferred | f typisdefined | t typdelim | , typrelid | 188542 typelem | 0 typarray | 188543 typinput | record_in typoutput | record_out typreceive | record_recv typsend | record_send typmodin | - typmodout | - typanalyze | - typalign | d typstorage | x typnotnull | f typbasetype | 0 typtypmod | -1 typndims | 0 typcollation | 0 typdefaultbin | typdefault | pgsql=#
pgsql=# select * from pg_type where typname='_tab10'; -[ RECORD 1 ]--+----------- typname | _tab10 typnamespace | 2200 typowner | 10 typlen | -1 typbyval | f typtype | b typcategory | A typispreferred | f typisdefined | t typdelim | , typrelid | 0 typelem | 188544 typarray | 0 typinput | array_in typoutput | array_out typreceive | array_recv typsend | array_send typmodin | - typmodout | - typanalyze | - typalign | d typstorage | x typnotnull | f typbasetype | 0 typtypmod | -1 typndims | 0 typcollation | 0 typdefaultbin | typdefault | pgsql=#
创建一个表达式后，对其他的系统表的写入，也有很多
再看和pg_depend之间的关联：
pgsql=# drop table tab10; DROP TABLE pgsql=# pgsql=# SELECT classid::regclass AS "depender object class", CASE classid WHEN 'pg_class'::regclass THEN objid::regclass::text WHEN 'pg_type'::regclass THEN objid::regtype::text WHEN 'pg_proc'::regclass THEN objid::regprocedure::text ELSE objid::text END AS "depender object identity", objsubid, refclassid::regclass AS "referenced object class", CASE refclassid WHEN 'pg_class'::regclass THEN refobjid::regclass::text WHEN 'pg_type'::regclass THEN refobjid::regtype::text WHEN 'pg_proc'::regclass THEN refobjid::regprocedure::text ELSE refobjid::text END AS "referenced object identity", refobjsubid, CASE deptype WHEN 'p' THEN 'pinned' WHEN 'i' THEN 'internal' WHEN 'a' THEN 'automatic' WHEN 'n' THEN 'normal' END AS "dependency type" FROM pg_catalog.pg_depend WHERE objid >= 16384 OR refobjid >= 16384; (No rows) pgsql=# pgsql=# create table tab10(id integer); CREATE TABLE pgsql=# SELECT classid::regclass AS "depender object class", CASE classid WHEN 'pg_class'::regclass THEN objid::regclass::text WHEN 'pg_type'::regclass THEN objid::regtype::text WHEN 'pg_proc'::regclass THEN objid::regprocedure::text ELSE objid::text END AS "depender object identity", objsubid, refclassid::regclass AS "referenced object class", CASE refclassid WHEN 'pg_class'::regclass THEN refobjid::regclass::text WHEN 'pg_type'::regclass THEN refobjid::regtype::text WHEN 'pg_proc'::regclass THEN refobjid::regprocedure::text ELSE refobjid::text END AS "referenced object identity", refobjsubid, CASE deptype WHEN 'p' THEN 'pinned' WHEN 'i' THEN 'internal' WHEN 'a' THEN 'automatic' WHEN 'n' THEN 'normal' END AS "dependency type" FROM pg_catalog.pg_depend WHERE objid >= 16384 OR refobjid >= 16384; -[ RECORD 1 ]--------------+------------- depender object class | pg_type depender object identity | tab10 objsubid | 0 referenced object class | pg_class referenced object identity | tab10 refobjsubid | 0 dependency type | internal -[ RECORD 2 ]--------------+------------- depender object class | pg_type depender object identity | tab10[] objsubid | 0 referenced object class | pg_type referenced object identity | tab10 refobjsubid | 0 dependency type | internal -[ RECORD 3 ]--------------+------------- depender object class | pg_class depender object identity | tab10 objsubid | 0 referenced object class | pg_namespace referenced object identity | 2200 refobjsubid | 0 dependency type | normal pgsql=#
再看对pg_class的影响：
pgsql=# drop table tab10; DROP TABLEpgsql=# create table tab10(id integer); CREATE TABLEpgsql=# \x Expanded display is on. pgsql=# select * from pg_class where relname='tab10'; -[ RECORD 1 ]--+------- relname | tab10 relnamespace | 2200 reltype | 188562 reloftype | 0 relowner | 10 relam | 0 relfilenode | 188560 reltablespace | 0 relpages | 0 reltuples | 0 reltoastrelid | 0 reltoastidxid | 0 relhasindex | f relisshared | f relpersistence | p relkind | r relnatts | 1 relchecks | 0 relhasoids | f relhaspkey | f relhasrules | f relhastriggers | f relhassubclass | f relfrozenxid | 2017 relacl | reloptions | pgsql=#
再看对 pg_attribute的影响，生成表之后：
pgsql=# select 188563::regclass; regclass ---------- tab10 (1 row) pgsql=# \x Expanded display is on. pgsql=# select * from pg_attribute where attrelid = (select max(attrelid) from pg_attribute); -[ RECORD 1 ]-+--------- attrelid | 188563 attname | tableoid atttypid | 26 attstattarget | 0 attlen | 4 attnum | -7 attndims | 0 attcacheoff | -1 atttypmod | -1 attbyval | t attstorage | p attalign | i attnotnull | t atthasdef | f attisdropped | f attislocal | t attinhcount | 0 attcollation | 0 attacl | attoptions | -[ RECORD 2 ]-+--------- attrelid | 188563 attname | cmax atttypid | 29 attstattarget | 0 attlen | 4 attnum | -6 attndims | 0 attcacheoff | -1 atttypmod | -1 attbyval | t attstorage | p attalign | i attnotnull | t atthasdef | f attisdropped | f attislocal | t attinhcount | 0 attcollation | 0 attacl | attoptions | -[ RECORD 3 ]-+--------- attrelid | 188563 attname | xmax atttypid | 28 attstattarget | 0 attlen | 4 attnum | -5 attndims | 0 attcacheoff | -1 atttypmod | -1 attbyval | t attstorage | p attalign | i attnotnull | t atthasdef | f attisdropped | f attislocal | t attinhcount | 0 attcollation | 0 attacl | attoptions | -[ RECORD 4 ]-+--------- attrelid | 188563 attname | cmin atttypid | 29 attstattarget | 0 attlen | 4 attnum | -4 attndims | 0 attcacheoff | -1 atttypmod | -1 attbyval | t attstorage | p attalign | i attnotnull | t atthasdef | f attisdropped | f attislocal | t attinhcount | 0 attcollation | 0 attacl | attoptions | -[ RECORD 5 ]-+--------- attrelid | 188563 attname | xmin atttypid | 28 attstattarget | 0 attlen | 4 attnum | -3 attndims | 0 attcacheoff | -1 atttypmod | -1 attbyval | t attstorage | p attalign | i attnotnull | t atthasdef | f attisdropped | f attislocal | t attinhcount | 0 attcollation | 0 attacl | attoptions | -[ RECORD 6 ]-+--------- attrelid | 188563 attname | ctid atttypid | 27 attstattarget | 0 attlen | 6 attnum | -1 attndims | 0 attcacheoff | -1 atttypmod | -1 attbyval | f attstorage | p attalign | s attnotnull | t atthasdef | f attisdropped | f attislocal | t attinhcount | 0 attcollation | 0 attacl | attoptions | -[ RECORD 7 ]-+--------- attrelid | 188563 attname | id atttypid | 23 attstattarget | -1 attlen | 4 attnum | 1 attndims | 0 attcacheoff | -1 atttypmod | -1 attbyval | t attstorage | p attalign | i attnotnull | f atthasdef | f attisdropped | f attislocal | t attinhcount | 0 attcollation | 0 attacl | attoptions | pgsql=#
基本就是这些了。
