数据泵TABLE_EXISTS_ACTION参数描述

本文详细介绍了使用IMPDP导入数据库时遇到表已存在情况时,四种处理方式(忽略、追加、替换、截断)的具体效果及操作步骤。通过实测展示了不同参数设置下对现有数据的影响,提供了实际应用时的选择依据。

当使用IMPDP完成数据库导入时,如遇到表已存在时,Oracle提供给我们如下四种处理方式:
a.忽略(SKIP,默认行为);
b.在原有数据基础上继续增加(APPEND);
c.先DROP表,然后创建表,最后完成数据插入(REPLACE);
d.先TRUNCATE,再完成数据插入(TRUNCATE)。

真实感受一下这几种方式的效果,供参考。

1.IMPDP在线帮助中关于TABLE_EXISTS_ACTION参数的描述
TABLE_EXISTS_ACTION   Action to take if imported object already exists.
                      Valid keywords: (SKIP), APPEND, REPLACE and TRUNCATE.

2.Oracle官方文档中的描述
http://download.oracle.com/docs/cd/B19306_01/server.102/b14215/dp_import.htm#sthref365
Oracle官方文档是根本,需研读。

3.使用EXPDP生成一份dump文件
sec@secDB /expdp$ expdp sec/sec directory=expdp_dir dumpfile=`date +"%Y%m%d%H%M%S"`_sec.dmp logfile=`date +"%Y%m%d%H%M%S"`_sec.log

Export: Release 10.2.0.3.0 - 64bit Production on Thursday, 01 April, 2010 10:29:17

Copyright (c) 2003, 2005, Oracle.  All rights reserved.

Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bit Production
With the Partitioning, Oracle Label Security, OLAP and Data Mining Scoring Engine options
Starting "SEC"."SYS_EXPORT_SCHEMA_01":  sec/******** directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec.log
Estimate in progress using BLOCKS method...
Processing object type SCHEMA_EXPORT/TABLE/TABLE_DATA
Total estimation using BLOCKS method: 3 MB
Processing object type SCHEMA_EXPORT/USER
Processing object type SCHEMA_EXPORT/SYSTEM_GRANT
Processing object type SCHEMA_EXPORT/ROLE_GRANT
Processing object type SCHEMA_EXPORT/DEFAULT_ROLE
Processing object type SCHEMA_EXPORT/PRE_SCHEMA/PROCACT_SCHEMA
Processing object type SCHEMA_EXPORT/TABLE/TABLE
Processing object type SCHEMA_EXPORT/TABLE/INDEX/INDEX
Processing object type SCHEMA_EXPORT/TABLE/CONSTRAINT/CONSTRAINT
Processing object type SCHEMA_EXPORT/TABLE/INDEX/STATISTICS/INDEX_STATISTICS
Processing object type SCHEMA_EXPORT/TABLE/COMMENT
. . exported "SEC"."T"                                   2.259 MB   24360 rows
Master table "SEC"."SYS_EXPORT_SCHEMA_01" successfully loaded/unloaded
******************************************************************************
Dump file set for SEC.SYS_EXPORT_SCHEMA_01 is:
  /expdp/20100401102917_sec.dmp
Job "SEC"."SYS_EXPORT_SCHEMA_01" successfully completed at 10:29:20

4.分别使用四中方式真实的感知一下具体效果
用到的IMPDP语句统一汇总在这里,方便参考。
impdp system/sys directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log TABLE_EXISTS_ACTION=SKIP
impdp system/sys directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log TABLE_EXISTS_ACTION=APPEND
impdp system/sys directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log TABLE_EXISTS_ACTION=REPLACE
impdp system/sys directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log TABLE_EXISTS_ACTION=TRUNCATE

1)默认行为SKIP
sec@ora10g> select count(*) from t;

  COUNT(*)
----------
     24360

sec@secDB /expdp$ impdp system/sys directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log

Import: Release 10.2.0.3.0 - 64bit Production on Thursday, 01 April, 2010 10:50:41

Copyright (c) 2003, 2005, Oracle.  All rights reserved.

Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bit Production
With the Partitioning, Oracle Label Security, OLAP and Data Mining Scoring Engine options
Master table "SYSTEM"."SYS_IMPORT_FULL_01" successfully loaded/unloaded
Starting "SYSTEM"."SYS_IMPORT_FULL_01":  system/******** directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log
Processing object type SCHEMA_EXPORT/USER
ORA-31684: Object type USER:"SEC" already exists
Processing object type SCHEMA_EXPORT/SYSTEM_GRANT
Processing object type SCHEMA_EXPORT/ROLE_GRANT
Processing object type SCHEMA_EXPORT/DEFAULT_ROLE
Processing object type SCHEMA_EXPORT/PRE_SCHEMA/PROCACT_SCHEMA
Processing object type SCHEMA_EXPORT/TABLE/TABLE
ORA-39151: Table "SEC"."T" exists. All dependent metadata and data will be skipped due to table_exists_action of skip
Processing object type SCHEMA_EXPORT/TABLE/TABLE_DATA
Job "SYSTEM"."SYS_IMPORT_FULL_01" completed with 2 error(s) at 10:50:42

上面的行为与下面一条显示的指定“SKIP”效果是一样的,不赘述。
sec@secDB /expdp$ impdp system/sys directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log TABLE_EXISTS_ACTION=SKIP

2)APPEND方式
sec@secDB /expdp$ impdp system/sys directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log TABLE_EXISTS_ACTION=APPEND

Import: Release 10.2.0.3.0 - 64bit Production on Thursday, 01 April, 2010 10:51:32

Copyright (c) 2003, 2005, Oracle.  All rights reserved.

Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bit Production
With the Partitioning, Oracle Label Security, OLAP and Data Mining Scoring Engine options
Master table "SYSTEM"."SYS_IMPORT_FULL_01" successfully loaded/unloaded
Starting "SYSTEM"."SYS_IMPORT_FULL_01":  system/******** directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log TABLE_EXISTS_ACTION=APPEND
Processing object type SCHEMA_EXPORT/USER
ORA-31684: Object type USER:"SEC" already exists
Processing object type SCHEMA_EXPORT/SYSTEM_GRANT
Processing object type SCHEMA_EXPORT/ROLE_GRANT
Processing object type SCHEMA_EXPORT/DEFAULT_ROLE
Processing object type SCHEMA_EXPORT/PRE_SCHEMA/PROCACT_SCHEMA
Processing object type SCHEMA_EXPORT/TABLE/TABLE
ORA-39152: Table "SEC"."T" exists. Data will be appended to existing table but all dependent metadata will be skipped due to table_exists_action of append
Processing object type SCHEMA_EXPORT/TABLE/TABLE_DATA
. . imported "SEC"."T"                                   2.259 MB   24360 rows
Job "SYSTEM"."SYS_IMPORT_FULL_01" completed with 2 error(s) at 10:51:33

此时表T的记录数翻倍。
sec@ora10g> select count(*) from t;

  COUNT(*)
----------
     48720

3)REPLACE方式
sec@secDB /expdp$ impdp system/sys directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log TABLE_EXISTS_ACTION=REPLACE

Import: Release 10.2.0.3.0 - 64bit Production on Thursday, 01 April, 2010 10:54:28

Copyright (c) 2003, 2005, Oracle.  All rights reserved.

Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bit Production
With the Partitioning, Oracle Label Security, OLAP and Data Mining Scoring Engine options
Master table "SYSTEM"."SYS_IMPORT_FULL_01" successfully loaded/unloaded
Starting "SYSTEM"."SYS_IMPORT_FULL_01":  system/******** directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log TABLE_EXISTS_ACTION=REPLACE
Processing object type SCHEMA_EXPORT/USER
ORA-31684: Object type USER:"SEC" already exists
Processing object type SCHEMA_EXPORT/SYSTEM_GRANT
Processing object type SCHEMA_EXPORT/ROLE_GRANT
Processing object type SCHEMA_EXPORT/DEFAULT_ROLE
Processing object type SCHEMA_EXPORT/PRE_SCHEMA/PROCACT_SCHEMA
Processing object type SCHEMA_EXPORT/TABLE/TABLE
Processing object type SCHEMA_EXPORT/TABLE/TABLE_DATA
. . imported "SEC"."T"                                   2.259 MB   24360 rows
Job "SYSTEM"."SYS_IMPORT_FULL_01" completed with 1 error(s) at 10:54:29

sec@ora10g> select count(*) from t;

  COUNT(*)
----------
     24360

4)TRUNCATE方式
sec@secDB /expdp$ impdp system/sys directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log TABLE_EXISTS_ACTION=TRUNCATE

Import: Release 10.2.0.3.0 - 64bit Production on Thursday, 01 April, 2010 10:54:55

Copyright (c) 2003, 2005, Oracle.  All rights reserved.

Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bit Production
With the Partitioning, Oracle Label Security, OLAP and Data Mining Scoring Engine options
Master table "SYSTEM"."SYS_IMPORT_FULL_01" successfully loaded/unloaded
Starting "SYSTEM"."SYS_IMPORT_FULL_01":  system/******** directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log TABLE_EXISTS_ACTION=TRUNCATE
Processing object type SCHEMA_EXPORT/USER
ORA-31684: Object type USER:"SEC" already exists
Processing object type SCHEMA_EXPORT/SYSTEM_GRANT
Processing object type SCHEMA_EXPORT/ROLE_GRANT
Processing object type SCHEMA_EXPORT/DEFAULT_ROLE
Processing object type SCHEMA_EXPORT/PRE_SCHEMA/PROCACT_SCHEMA
Processing object type SCHEMA_EXPORT/TABLE/TABLE
ORA-39153: Table "SEC"."T" exists and has been truncated. Data will be loaded but all dependent metadata will be skipped due to table_exists_action of truncate
Processing object type SCHEMA_EXPORT/TABLE/TABLE_DATA
. . imported "SEC"."T"                                   2.259 MB   24360 rows
Job "SYSTEM"."SYS_IMPORT_FULL_01" completed with 2 error(s) at 10:54:56

sec@ora10g> select count(*) from t;

  COUNT(*)
----------
     24360

 

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转载于:http://blog.itpub.net/26179867/viewspace-707730/

`table_exists_action` 是一个常用于数据库操作中的参数或命令,尤其在涉及数据库迁移、元数据操作或数据导入导出工具中较为常见。该参数通常用于指定当目标表已经存在时应采取的操作。不同的数据库管理系统(DBMS)或框架可能对该参数的支持有所不同,但其核心用途是相似的。 在数据迁移或导入场景中,例如使用 `mysqldump` 或某些 ORM(如 SQLAlchemy、Django ORM)进行数据导入时,`table_exists_action` 可以控制程序如何处理目标数据库中已经存在的表[^1]。常见的取值包括: - **fail**:如果目标表已存在,则操作失败并抛出错误。 - **replace**:如果目标表已存在,则先删除(或截断)表,再重新创建并导入数据。 - **append**:如果目标表已存在,则直接向表中追加数据。 - **drop**:删除已存在的表并重新创建。 以下是一个可能的使用示例,假设在某个数据库迁移工具中配置了该参数: ```yaml import_config: table_exists_action: replace source_file: data.sql target_table: users ``` 在某些框架中,比如 Apache NiFi 或 Sqoop,类似的逻辑也可能存在,尽管具体参数名称可能略有不同。通常,`table_exists_action` 与 SQL 操作中的 `IF NOT EXISTS` 子句形成对比,后者用于在创建表时避免因表已存在而导致的错误[^1]。 此外,结合数据库操作中的 SQL 模式设置(如引用中提到的 `sql_mode=ONLY_FULL_GROUP_BY` 等),`table_exists_action` 的行为可能还会受到数据库全局或会话级别的 SQL 模式影响,尤其是在严格模式下(如 `STRICT_TRANS_TABLES`),数据库会更倾向于拒绝不符合预期的操作而不是自动修正或忽略错误[^1]。 ### 使用建议 - 在生产环境中使用 `table_exists_action` 时,应特别小心 `replace` 或 `drop` 操作,因为它们可能导致数据丢失。 - 对于数据导入任务,建议在执行前进行预检查,确认目标表的状态,并根据需要选择合适的 `table_exists_action` 策略。 - 如果使用的是框架或库,查阅其文档以确认支持的取值及具体行为。
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