ORACLE ---- 和PostgreSQL繼承表相似的實現方式

時間 2021-06-18

標籤數據庫 oracle code 繼承索引 get table test object 欄目 Oracle 简体版

原文原文鏈接

昨天介紹了PostgreSQL裏的繼承表，今天來繼續討論ORACLE數據庫裏有沒有相似的東西。數據庫

首先，能夠明確的說，ORACLE數據庫裏沒有繼承表這種OBJECT。
可是，和PostgreSQL的繼承表相似，不一樣Table的數據以某種方式進行關聯，共享存儲空間的角度來說，ORACLE數據庫也存在這樣的OBJECT。oracle

那就是CLUSTER。code

首先，ORACLE數據庫對「CLUSTER」是這樣定義的：繼承

CREATE CLUSTER (oracle.com)
A cluster is a schema object that contains data from one or more tables.

下面咱們來看看CLUSTER是怎樣應用的。索引

--作成CLUSTER
SQL> conn test/test@localhost:1521/pdb
接続されました。
SQL> CREATE CLUSTER object
   (object VARCHAR2(23))
SIZE 512
STORAGE (initial 100K next 50K);  2    3    4

クラスタが做成されました。

--爲CLUSTR作一個索引
SQL> CREATE INDEX idx_object ON CLUSTER object;

索引が做成されました。

--作成使用CLUSTER的第一個表
SQL> CREATE TABLE object_table
   CLUSTER object (OBJECT_TYPE)
   AS SELECT * FROM dba_objects WHERE OBJECT_TYPE = 'TABLE';  2    3

表が做成されました。

--作成使用CLUSTER的第二個表
SQL> CREATE TABLE object_index
   CLUSTER object (OBJECT_TYPE)
   AS SELECT * FROM dba_objects WHERE OBJECT_TYPE = 'INDEX';  2    3

表が做成されました。

--確認一下兩個表的狀態和定義
SQL> select count(*) from object_index;

  COUNT(*)
----------
      2898

SQL> select count(*) from object_table;

  COUNT(*)
----------
      2223

SQL> @obj
object_nameに値を入力してください: object_index
舊   1: select owner,object_name,object_type from dba_objects where object_name like upper('&object_name')
新   1: select owner,object_name,object_type from dba_objects where object_name like upper('object_index')

OWNER                OBJECT_NAME                                        OBJECT_TYPE
-------------------- -------------------------------------------------- -----------------------
TEST                 OBJECT_INDEX                                       TABLE

SQL> @obj
object_nameに値を入力してください: object_table
舊   1: select owner,object_name,object_type from dba_objects where object_name like upper('&object_name')
新   1: select owner,object_name,object_type from dba_objects where object_name like upper('object_table')

OWNER                OBJECT_NAME                                        OBJECT_TYPE
-------------------- -------------------------------------------------- -----------------------
TEST                 OBJECT_TABLE                                       TABLE

SQL> @ddl
object_typeに値を入力してください: TABLE
object_nameに値を入力してください: OBJECT_INDEX
ownerに値を入力してください: TEST
舊   1: select dbms_metadata.get_ddl('&object_type','&object_name','&owner') from dual
新   1: select dbms_metadata.get_ddl('TABLE','OBJECT_INDEX','TEST') from dual

DBMS_METADATA.GET_DDL('TABLE','OBJECT_INDEX','TEST')
--------------------------------------------------------------------------------

  CREATE TABLE "TEST"."OBJECT_INDEX"
   (    "OWNER" VARCHAR2(128),
        "OBJECT_NAME" VARCHAR2(128),
        "SUBOBJECT_NAME" VARCHAR2(128),
        "OBJECT_ID" NUMBER,
        "DATA_OBJECT_ID" NUMBER,
        "OBJECT_TYPE" VARCHAR2(23),
        "CREATED" DATE,
        "LAST_DDL_TIME" DATE,
        "TIMESTAMP" VARCHAR2(19),
        "STATUS" VARCHAR2(7),
        "TEMPORARY" VARCHAR2(1),
        "GENERATED" VARCHAR2(1),
        "SECONDARY" VARCHAR2(1),
        "NAMESPACE" NUMBER,
        "EDITION_NAME" VARCHAR2(128),
        "SHARING" VARCHAR2(18),
        "EDITIONABLE" VARCHAR2(1),
        "ORACLE_MAINTAINED" VARCHAR2(1),
        "APPLICATION" VARCHAR2(1),
        "DEFAULT_COLLATION" VARCHAR2(100),
        "DUPLICATED" VARCHAR2(1),
        "SHARDED" VARCHAR2(1),
        "CREATED_APPID" NUMBER,
        "CREATED_VSNID" NUMBER,
        "MODIFIED_APPID" NUMBER,
        "MODIFIED_VSNID" NUMBER
   ) CLUSTER "TEST"."OBJECT" ("OBJECT_TYPE")

SQL> @ddl
object_typeに値を入力してください: TABLE
object_nameに値を入力してください: OBJECT_TABLE
ownerに値を入力してください: TEST
舊   1: select dbms_metadata.get_ddl('&object_type','&object_name','&owner') from dual
新   1: select dbms_metadata.get_ddl('TABLE','OBJECT_TABLE','TEST') from dual

DBMS_METADATA.GET_DDL('TABLE','OBJECT_TABLE','TEST')
--------------------------------------------------------------------------------

  CREATE TABLE "TEST"."OBJECT_TABLE"
   (    "OWNER" VARCHAR2(128),
        "OBJECT_NAME" VARCHAR2(128),
        "SUBOBJECT_NAME" VARCHAR2(128),
        "OBJECT_ID" NUMBER,
        "DATA_OBJECT_ID" NUMBER,
        "OBJECT_TYPE" VARCHAR2(23),
        "CREATED" DATE,
        "LAST_DDL_TIME" DATE,
        "TIMESTAMP" VARCHAR2(19),
        "STATUS" VARCHAR2(7),
        "TEMPORARY" VARCHAR2(1),
        "GENERATED" VARCHAR2(1),
        "SECONDARY" VARCHAR2(1),
        "NAMESPACE" NUMBER,
        "EDITION_NAME" VARCHAR2(128),
        "SHARING" VARCHAR2(18),
        "EDITIONABLE" VARCHAR2(1),
        "ORACLE_MAINTAINED" VARCHAR2(1),
        "APPLICATION" VARCHAR2(1),
        "DEFAULT_COLLATION" VARCHAR2(100),
        "DUPLICATED" VARCHAR2(1),
        "SHARDED" VARCHAR2(1),
        "CREATED_APPID" NUMBER,
        "CREATED_VSNID" NUMBER,
        "MODIFIED_APPID" NUMBER,
        "MODIFIED_VSNID" NUMBER
   ) CLUSTER "TEST"."OBJECT" ("OBJECT_TYPE")

--確認一下兩個表的存儲狀況
col OWNER for a10
col SEGMENT_NAME for a20
col SEGMENT_TYPE for a18
col SEGMENT_SUBTYPE for a10
col TABLESPACE_NAME for a10
col RETENTION for a7
set lin 200 pages 999

select OWNER,SEGMENT_NAME,SEGMENT_TYPE,SEGMENT_SUBTYPE,TABLESPACE_NAME,HEADER_FILE,HEADER_BLOCK,BLOCKS,EXTENTS,RETENTION 
from dba_segments 
where OWNER='TEST';

OWNER      SEGMENT_NAME         SEGMENT_TYPE       SEGMENT_SU TABLESPACE HEADER_FILE HEADER_BLOCK     BLOCKS    EXTENTS RETENTI
---------- -------------------- ------------------ ---------- ---------- ----------- ------------ ---------- ---------- -------
TEST       OBJECT               CLUSTER            ASSM       USERS               12          130         96         12
TEST       IDX_OBJECT           INDEX              ASSM       USERS               12          146          8          1

OK，已經能夠確認到使用CLUSTER的兩張表確實共享了存儲空間。get

固然，ORACLE數據庫的CLUSTER和PostgreSQL繼承表並非相同的東西，上面的例子只是從多張表共享物理存儲空間的角度進行了分析,至於其餘的角度，就見仁見智了。it

2021/06/18 @ Daliantable