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Greenplum6 数据库数据库学习_外部表

来源:互联网 作者:佚名 时间:2022-07-19 11:10
学习地址 注意,以下文档可能有问题,以实际测试为准。因为版本6语法有变化。https://www.cnblogs.com/kingle-study/p/10552097.html书籍《Greenplum企业应用实战》 外部表简介 Greenplum 在数据加载上

学习地址

注意,以下文档可能有问题,以实际测试为准。因为版本6语法有变化。https://www.cnblogs.com/kingle-study/p/10552097.html书籍《Greenplum企业应用实战》

外部表简介

Greenplum 在数据加载上有一个明显的优势,就是支持数据的并发加载,gpfdisk是并发加载的工具,数据库中对应的就是外部表   所谓外部表,就是在数据库中只有表定义、没有数据,数据都存放在数据库之外的数据文件。greenplum可以对一个外部表执行正常的DML操作,当读取数据的时候,数据库从数据文件中加载数据。外部表支持在segment上并发地告诉从gpfdist导入数据,由于是从segment上导入数据,所以效率很高。

  结构图:

Greenplum6 数据库数据库学习_外部表

  外部表需要指定gpfdist的IP和端口,还要有详细的目录地址,文件名支持通配符匹配。可以编写多个gpfdist地址,但是总数不能超过总的segment数量,否则会报错。   GPDB提供两种外部表:可读外部表用于数据装载、可写外部表用于数据卸载。外部表可基于文件、亦可基于WEB,这两种都能实现可读、可写。 当一个查询使用一个常规的外部表,该外部表被认为是可重读的,因为在该查询期间数据是静态的。而对于WEB外部表,数据是不可重读的,因为在该查询的执行期间数据可能会发生变化。     可写外部表用以从数据库表中选择记录并输出到文件、命名管道或其他可执行程序。 比如,可以从GPDB中卸载数据并发送到一个可执行程序,该程序连接到其他数据库或者ETL工具并装载数据到其他地方。 可写外部表还可以用于输出到GPDB的并行MapReduce计算。     可写外部表被定义后,数据即可从数据库表中被选择并插入到该可写外部表。 可写外部表只允许INSERT操作 – SELECT、 UPDATE、 DELETE或TRUNCATE是不允许的。可写外部表输出数据到一个可执行程序,该程序要能够接受流输入数据。     在创建外部表的时候,可以指定分隔符、err表、指定允许出错的数据条数,以及源文件的编码等信息。

语法

CREATE [READABLE] EXTERNAL [TEMPORARY | TEMP] TABLE table_name ( column_name data_type [, ...] | LIKE other_table ) LOCATION ('file://seghost[:port]/path/file' [, ...]) | ('gpfdist://filehost[:port]/file_pattern[#transform]' | ('gpfdists://filehost[:port]/file_pattern[#transform]' [, ...]) FORMAT 'TEXT' [( [HEADER] [DELIMITER [AS] 'delimiter' | 'OFF'] [NULL [AS] 'null string'] [ESCAPE [AS] 'escape' | 'OFF'] [NEWLINE [ AS ] 'LF' | 'CR' | 'CRLF'] [FILL MISSING FIELDS] )] | 'CSV' [( [HEADER] [QUOTE [AS] 'quote'] [DELIMITER [AS] 'delimiter'] [NULL [AS] 'null string'] [FORCE NOT NULL column [, ...]] [ESCAPE [AS] 'escape'] [NEWLINE [ AS ] 'LF' | 'CR' | 'CRLF'] [FILL MISSING FIELDS] )] | 'CUSTOM' (Formatter=<formatter specifications>) [ ENCODING 'encoding' ] [ [LOG ERRORS] SEGMENT REJECT LIMIT count [ROWS | PERCENT] ] CREATE [READABLE] EXTERNAL WEB [TEMPORARY | TEMP] TABLE table_name ( column_name data_type [, ...] | LIKE other_table ) LOCATION ('http://webhost[:port]/path/file' [, ...]) | EXECUTE 'command' [ON ALL | MASTER | number_of_segments | HOST ['segment_hostname'] | SEGMENT segment_id ] FORMAT 'TEXT' [( [HEADER] [DELIMITER [AS] 'delimiter' | 'OFF'] [NULL [AS] 'null string'] [ESCAPE [AS] 'escape' | 'OFF'] [NEWLINE [ AS ] 'LF' | 'CR' | 'CRLF'] [FILL MISSING FIELDS] )] | 'CSV' [( [HEADER] [QUOTE [AS] 'quote'] [DELIMITER [AS] 'delimiter'] [NULL [AS] 'null string'] [FORCE NOT NULL column [, ...]] [ESCAPE [AS] 'escape'] [NEWLINE [ AS ] 'LF' | 'CR' | 'CRLF'] [FILL MISSING FIELDS] )] | 'CUSTOM' (Formatter=<formatter specifications>) [ ENCODING 'encoding' ] [ [LOG ERRORS] SEGMENT REJECT LIMIT count [ROWS | PERCENT] ] CREATE WRITABLE EXTERNAL [TEMPORARY | TEMP] TABLE table_name ( column_name data_type [, ...] | LIKE other_table ) LOCATION('gpfdist://outputhost[:port]/filename[#transform]' | ('gpfdists://outputhost[:port]/file_pattern[#transform]' [, ...]) FORMAT 'TEXT' [( [DELIMITER [AS] 'delimiter'] [NULL [AS] 'null string'] [ESCAPE [AS] 'escape' | 'OFF'] )] | 'CSV' [([QUOTE [AS] 'quote'] [DELIMITER [AS] 'delimiter'] [NULL [AS] 'null string'] [FORCE QUOTE column [, ...]] ] [ESCAPE [AS] 'escape'] )] | 'CUSTOM' (Formatter=<formatter specifications>) [ ENCODING 'write_encoding' ] [ DISTRIBUTED BY (column [opclass], [ ... ] ) | DISTRIBUTED RANDOMLY ] CREATE WRITABLE EXTERNAL WEB [TEMPORARY | TEMP] TABLE table_name ( column_name data_type [, ...] | LIKE other_table ) EXECUTE 'command' [ON ALL] FORMAT 'TEXT' [( [DELIMITER [AS] 'delimiter'] [NULL [AS] 'null string'] [ESCAPE [AS] 'escape' | 'OFF'] )] | 'CSV' [([QUOTE [AS] 'quote'] [DELIMITER [AS] 'delimiter'] [NULL [AS] 'null string'] [FORCE QUOTE column [, ...]] ] [ESCAPE [AS] 'escape'] )] | 'CUSTOM' (Formatter=<formatter specifications>) [ ENCODING 'write_encoding' ] [ DISTRIBUTED BY (column [opclass], [ ... ] ) | DISTRIBUTED RANDOMLY ] testDB=#

创建外部表

语法

gpfdist [-d directory] [-p http_port] [-l log_file] [-t timeout] [-S] [-w time] [-v | -V] [-s] [-m max_length] [--ssl certificate_path] gpfdist -? | --help gpfdist --version

启动进程

[gpadmin@mdw ~]$ nohup gpfdist -d /home/gpadmin/script/ -p 8081 -l /home/gpadmin/script/gpfdist.log & [1] 32971 [gpadmin@mdw ~]$ nohup: ignoring input and appending output to ‘nohup.out’ [gpadmin@mdw ~]$ [gpadmin@mdw ~]$ [gpadmin@mdw ~]$ [gpadmin@mdw ~]$ [gpadmin@mdw ~]$ ll total 75448 drwxrwxr-x 2 gpadmin gpadmin 4096 Apr 14 22:51 gpAdminLogs drwxrwxr-x 2 gpadmin gpadmin 41 Feb 16 16:27 gpconfig drwxr-xr-x 2 gpadmin gpadmin 195 Feb 23 21:43 greenplum-cc-web-6.4.0-gp6-rhel7-x86_64 -rw-r--r-- 1 gpadmin gpadmin 77241507 Feb 17 23:01 greenplum-cc-web-6.4.0-gp6-rhel7-x86_64.zip -rw-rw-r-- 1 gpadmin gpadmin 2733 Feb 23 20:49 initGreenplum  drwxrwxr-x 2 gpadmin gpadmin 61 Mar 15 16:33 l -rw------- 1 gpadmin gpadmin 583 Apr 15 01:15 nohup.out -rw-rw-r-- 1 gpadmin gpadmin 84 Apr 14 22:51 recov drwxrwxr-x 2 gpadmin gpadmin 25 Apr 15 01:15 script [gpadmin@mdw ~]$ jobs [1]+ Running nohup gpfdist -d /home/gpadmin/script/ -p 8081 -l /home/gpadmin/script/gpfdist.log & [gpadmin@mdw ~]$ cd script/ [gpadmin@mdw script]$ ls gpfdist.log [gpadmin@mdw script]$ more gpfdist.log [gpadmin@mdw script]$ ss -lntup|grep 8081 tcp LISTEN 0 256 [::]:8081 [::]:* users:(("gpfdist",pid=32971,fd=6)) [gpadmin@mdw script]$ [gpadmin@mdw script]$ [gpadmin@mdw script]$ vim test.txt Prague,Jan,101,4875.33 Rome,Mar,87,1557.39 Bangalore,May,317,8936.99 Beijing,Jul,411,11600.67 San Francisco,Sept,156,6846.34 Paris,Nov,159,7134.56 San Francisco,Jan,113,5397.89 Prague,Dec,333,9894.77 Bangalore,Jul,271,8320.55 Beijing,Dec,100,4248.41

创建外部表

create external table public.test ( country varchar(128), name varchar(128), id int, sale varchar(128) ) location ('gpfdist://10.10.10.101:8081/test.txt') format 'text' (delimiter ',' null as '' escape 'off') encoding 'utf8' log errors segment reject limit 3 rows; --- location 文件所在位置,可以直接是本地路径、gpfdist地址、gpfdists地址、gphdfs地址。 --- format 文本类型 --- delimiter 分隔符 --- encoding 编码 --- log errors into 错误数据表,记录错误数据,会自动创建。一般都是tablename_err格式,例如t1_err。 --- segment reject limit 错误数据的条数/百分比(rows/percent),超过设置值会报错。最小值是2。用来确保数据的完整性。 testDB=# create external table public.test testDB-# ( testDB(# country varchar(128), testDB(# name varchar(128), testDB(# id int, testDB(# sale varchar(128) testDB(# ) testDB-# location ('gpfdist://10.10.10.101:8081/test.txt') testDB-# format 'text' testDB-# (delimiter ',' null as '' escape 'off') testDB-# encoding 'utf8' testDB-# log errors segment reject limit 3 rows; CREATE EXTERNAL TABLE testDB=# testDB=# testDB=# select * from public.test; country | name | id | sale ---------------+------+-----+---------- Prague | Jan | 101 | 4875.33 Rome | Mar | 87 | 1557.39 Bangalore | May | 317 | 8936.99 Beijing | Jul | 411 | 11600.67 San Francisco | Sept | 156 | 6846.34 Paris | Nov | 159 | 7134.56 San Francisco | Jan | 113 | 5397.89 Prague | Dec | 333 | 9894.77 Bangalore | Jul | 271 | 8320.55 Beijing | Dec | 100 | 4248.41 (10 rows)

数据装载

表结构必须存在

testDB=# create table public.test_in testDB-# ( testDB(# country varchar(128), testDB(# name varchar(128), testDB(# id int, testDB(# sale varchar(128) testDB(# ) testDB-# ; NOTICE: Table doesn't have 'DISTRIBUTED BY' clause -- Using column named 'country' as the Greenplum Database data distribution key for this table. HINT: The 'DISTRIBUTED BY' clause determines the distribution of data. Make sure column(s) chosen are the optimal data distribution key to minimize skew. CREATE TABLE testDB=# insert into test_in select * from public.test; INSERT 0 10 testDB=#

如果表结构不存在,则会插入不进去

testDB=# insert into testx001 select * from public.test; ERROR: relation "testx001" does not exist LINE 1: insert into testx001 select * from public.test;
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