oracle_fdw安裝及使用（無法訪問oracle存儲過程等對象）

通過oracle_fdw可以訪問oracle中的一些表和視圖，也可以進行修改，尤其是給比較復雜的系統使用非常方便。

 

（但不能使用oracle_fdw來訪問oracle的存儲過程、包、函數、序列等對象） 

 

1.安裝oracle_fdw:

 

1）編譯安裝oracle_fdw之前，需要安裝Oracle的客戶端程序;下載地址：http://www.oracle.com/technetwork/database/database-technologies/instant-client/overview/index.html

 

主要是sdk和basic：

instantclient-basic-linux.x64-18.5.0.0.0dbru.zip

instantclient-sdk-linux.x64-18.5.0.0.0dbru.zip

 

2）下載地址：http://pgxn.org/dist/oracle_fdw/

unzip oracle_fdw-2.1.0.zip

cd oracle_fdw-2.1.0

 

3）配置環境變量：

[root@fce40690-0e46-4603-e80e-ca351bda31ec ~]# cat ora-env.sh

export ORACLE_HOME=/opt/oracle/instantclient

export OCI_LIB_DIR=$ORACLE_HOME

export OCI_INC_DIR=$ORACLE_HOME/sdk/include

 

[root@fce40690-0e46-4603-e80e-ca351bda31ec ~]# cat pg-env.sh

[ -f /etc/profile ] && source /etc/profile

PGDATA=/var/lib/pgsql/11/data

export PGDATA

# If you want to customize your settings,

# Use the file below. This is not overridden

# by the RPMS.

[ -f /var/lib/pgsql/.pgsql_profile ] && source /var/lib/pgsql/.pgsql_profile

 

export PGHOME=/usr/pgsql-11/

export LD_LIBRARY_PATH=$PGHOME/lib:$LD_LIBRARY_PATH:/opt/oracle/instantclient/

export PATH=$PATH:$PGHOME/bin

 

4）編譯安裝：

make && make install

 

5）切換到postgres創建擴展

postgres=# create extension oracle_fdw;

如果出現找不到libclntsh.so.12.1等庫，則考慮將缺少的庫從/opt/oracle/instantclient/中拷貝到postgres安裝目錄的lib下面，有些情況下，指定了LD_LIBRARY_PATH目錄都會提示找不到。

postgres=# \dx
List of installed extensions
Name | Version | Schema | Description
------------+---------+------------+----------------------------------------
oracle_fdw | 1.1 | public | foreign data wrapper for Oracle access
plpgsql | 1.0 | pg_catalog | PL/pgSQL procedural language
(2 rows)

 

2.配置oracle數據庫tnsnames.ora

可以將Oracle那邊的對應文件拷貝過來即可，注意里面的IP地址：

[postgres@fce40690-0e46-4603-e80e-ca351bda31ec ~]$ cat /opt/oracle/instantclient/network/admin/tnsnames.ora

# tnsnames.ora Network Configuration File: /ora/oracle/product/11.2.0/dbhome_1/network/admin/tnsnames.ora

# Generated by Oracle configuration tools.

 

ORCL =

  (DESCRIPTION =

    (ADDRESS = (PROTOCOL = TCP)(HOST = 10.9.10.236)(PORT = 1521))

    (CONNECT_DATA =

      (SERVER = DEDICATED)

      (SERVICE_NAME = orcl)

    )

  )

 

3.創建外部表

 

1）創建server：

create server oracle_test foreign data wrapper oracle_fdw options(dbserver 'ORCL');

 

 

2）創建mapping：

create user mapping for postgres server oracle_test options (user 'oracle', password 'oracle');

 

3）創建外部表：

CREATE FOREIGN TABLE test(

id int

) SERVER oracle_test options (schema 'ORACLE', table 'TEST');

 

 

4）檢查：

postgres=# select oracle_diag();

                         oracle_diag

-------------------------------------------------------------

 oracle_fdw 2.1.0, PostgreSQL 11.2, Oracle client 18.5.0.0.0

(1 row)

 

5）查詢：

postgres=# select * from test;

 id

----

  1

(1 row)

 

6）查看外部表相關對象：

postgres=# \des
            List of foreign servers
    Name     |  Owner   | Foreign-data wrapper
-------------+----------+----------------------
 oracle_test | postgres | oracle_fdw
(1 row)

postgres=# \deu
  List of user mappings
   Server    | User name
-------------+-----------
 oracle_test | postgres
(1 row)

postgres=# \det
       List of foreign tables
 Schema |    Table    |   Server
--------+-------------+-------------
 public | test        | oracle_test
 public | test_no_fdw | oracle_test
 public | test_seq    | oracle_test
(3 rows)

 

 

4.在查詢時如果提示錯誤：ORA-12154

postgres=# select * from test;

ERROR:  connection for foreign table "test" cannot be established

DETAIL:  ORA-12154: TNS:could not resolve the connect identifier specified

 

1）確認環境變量是否在postgres用戶下設置

2）確認oracle的instantclient是否有postgres的訪問權限

 

5.外部表的一些配置選項：

Foreign table options

table (required)

The Oracle table name. This name must be written exactly as it occurs in Oracle's system catalog, so normally consist of uppercase letters only.

To define a foreign table based on an arbitrary Oracle query, set this option to the query enclosed in parentheses, e.g.

OPTIONS (table '(SELECT col FROM tab WHERE val = ''string'')')
Do not set the schema option in this case.
INSERT, UPDATE and DELETE will work on foreign tables defined on simple queries; if you want to avoid that (or confusing Oracle error messages for more complicated queries), use the table option readonly.

schema (optional)

The table's schema (or owner). Useful to access tables that do not belong to the connecting Oracle user. This name must be written exactly as it occurs in Oracle's system catalog, so normally consist of uppercase letters only.

max_long (optional, defaults to "32767")

The maximal length of any LONG or LONG RAW columns in the Oracle table. Possible values are integers between 1 and 1073741823 (the maximal size of a bytea in PostgreSQL). This amount of memory will be allocated at least twice, so large values will consume a lot of memory.
If max_long is less than the length of the longest value retrieved, you will receive the error message ORA-01406: fetched column value was truncated.

readonly (optional, defaults to "false")

INSERT, UPDATE and DELETE is only allowed on tables where this option is not set to yes/on/true. Since these statements can only be executed from PostgreSQL 9.3 on, setting this option has no effect on earlier versions. It might still be a good idea to set it in PostgreSQL 9.2 and earlier on tables that you do not wish to be changed, to be prepared for an upgrade to PostgreSQL 9.3 or later.

sample_percent (optional, defaults to "100")

This option only influences ANALYZE processing and can be useful to ANALYZE very large tables in a reasonable time.

The value must be between 0.000001 and 100 and defines the percentage of Oracle table blocks that will be randomly selected to calculate PostgreSQL table statistics. This is accomplished using the SAMPLE BLOCK (x) clause in Oracle.

ANALYZE will fail with ORA-00933 for tables defined with Oracle queries and may fail with ORA-01446 for tables defined with complex Oracle views.

prefetch (optional, defaults to "200")

Sets the number of rows that will be fetched with a single round-trip between PostgreSQL and Oracle during a foreign table scan. This is implemented using Oracle row prefetching. The value must be between 0 and 10240, where a value of zero disables prefetching.

Higher values can speed up performance, but will use more memory on the PostgreSQL server.

 

但是在實際操作過程中，往往會遇到oracle中通dblink訪問其他數據庫創建的synonym（同義詞），這些同義詞包括了表、視圖、序列、包，那么是否可以通過oracle_fdw來訪問序列和包呢？

oracle_fdw的外部表可以是一個SQL語句，基於此，下面做一些實驗：

 

6.通過oracle_fdw訪問oracle的序列、包和函數等對象：

1）測試序列

oracle端：

create sequence test_id_seq

start with 1

increment by 1

nomaxvalue

nominvalue

nocycle

nocache;

 

select test_id_seq.nextval from dual;

 

pg端：

drop foreign table test_seq;

CREATE FOREIGN TABLE test_seq(

id int

) SERVER oracle_test options (table '(select test_id_seq.nextval from dual)', readonly 'yes');

 

不能配置schema名稱，SQL要用括號括起來。

但還是報錯：

postgres=# select * from test_seq;

ERROR:  error describing remote table: OCIStmtExecute failed to describe table

DETAIL:  ORA-02287: sequence number not allowed here

 

說明不能通過外部表的方式訪問序列？？？

 

測試訪問表的SQL：

drop foreign table test_seq;

CREATE FOREIGN TABLE test_seq(

id int

) SERVER oracle_test options (table '(select * from test)', readonly 'yes');

select * from test_seq;

postgres=#

 id

----

  1

(1 row)

 

測試訪問一個沒有定義為外部表的表：

drop foreign table test_no_fdw;

CREATE FOREIGN TABLE test_no_fdw(

id int

) SERVER oracle_test options (table '(select * from test2)', readonly 'yes');

select * from test_no_fdw;

postgres=#

 id

----

  1

  1

  1

(3 rows)

 

可以訪問，說明可以通過這種方式來下放表的jion，因為說明文檔中說了，兩個外部表的jion會下推到oracle端，增強效率，但是兩個表都應該是外部表。

現在又多了一種選擇。

 

2）測試函數：

#如果函數有入參怎么處理？

下面實驗一下沒有入參的函數，看看能否訪問：

實驗存儲過程：

Oracle端：

create or replace PROCEDURE firstPro

         IS

         BEGIN

         DBMS_OUTPUT.PUT_LINE('Hello World!');

         END;

 

pg端：

drop foreign table test_procdure;

CREATE FOREIGN TABLE test_procdure(

info text

) SERVER oracle_test options (table '(begin firstPro(); end;)', readonly 'yes');

select * from test_procdure;

 

postgres=# select * from test_procdure;

ERROR:  error describing remote table: OCIStmtExecute failed to describe table

DETAIL:  ORA-00907: missing right parenthesis

postgres=# \d+ test_procdure

                                 Foreign table "public.test_procdure"

 Column | Type | Collation | Nullable | Default | FDW options | Storage  | Stats target | Description

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

 info   | text |           |          |         |             | extended |              |

Server: oracle_test

FDW options: ("table" '(begin firstPro(); end;)', readonly 'yes')

 

結論是不能用。