Greenplum6 数据库数据库学习_外部表

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》

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:

　　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。

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=# 

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

[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 ~]$ lltotal 75448drwxrwxr-x 2 gpadmin gpadmin     4096 Apr 14 22:51 gpAdminLogsdrwxrwxr-x 2 gpadmin gpadmin       41 Feb 16 16:27 gpconfigdrwxr-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 recovdrwxrwxr-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]$ lsgpfdist.log[gpadmin@mdw script]$ more gpfdist.log [gpadmin@mdw script]$ ss -lntup|grep 8081tcp    LISTEN     0      256    [::]:8081               [::]:*                   users:(("gpfdist",pid=32971,fd=6))[gpadmin@mdw script]$ [gpadmin@mdw script]$ [gpadmin@mdw script]$ vim test.txtPrague,Jan,101,4875.33Rome,Mar,87,1557.39Bangalore,May,317,8936.99Beijing,Jul,411,11600.67San Francisco,Sept,156,6846.34Paris,Nov,159,7134.56San Francisco,Jan,113,5397.89Prague,Dec,333,9894.77Bangalore,Jul,271,8320.55Beijing,Dec,100,4248.41

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.testtestDB-# (testDB(# country va����,����rchar(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 TABLEtestDB=#        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)

表结构必须存在

testDB=# create  table public.test_intestDB-# (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 TABLEtestDB=# insert into  test_in select * from  public.test;INSERT 0 10testDB=# 

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 existLINE 1: insert into testx001 select * from  public.test;