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最近在折腾greenplum，遇到一个蛋疼的问题，那就是获取表结构，也就是建表语句。大家都知道在MySQL里面是非常easy的，show create table table_name 就搞定了，在gpdb里面就没这么容易，在查询大量资料以后终于找到了方法。那就是自己定义一个函数去获取，函数中可以嵌套python代码，非常的方便。但是资料中的代码有大量错误，在经过几番调试以后终于可以使用了。

如果没有这个函数其实也可以获取表结构，那就是只能导出这个表的结构进行查看了。导出表结构的命令是：

pg_dump -s --table=tb1_partition_range_yyyymmdd testdb > tb1_partition_range_yyyymmdd.sql

查看表结构：

[gpadmin@mdw ~]$ cat tb1_partition_range_yyyymmdd.sql ---- Greenplum Database database dump--SET statement_timeout = 0;SET client_encoding = 'UTF8';SET standard_conforming_strings = off;SET check_function_bodies = false;SET client_min_messages = warning;SET escape_string_warning = off;SET search_path = public, pg_catalog;SET default_tablespace = '';SET default_with_oids = false;---- Name: tb1_partition_range_yyyymmdd; Type: TABLE; Schema: public; Owner: gpadmin; Tablespace: --CREATE TABLE tb1_partition_range_yyyymmdd (    id numeric,    yyyymmdd date)WITH (appendonly=true, compresslevel=5) DISTRIBUTED BY (id) PARTITION BY RANGE(yyyymmdd)           (          PARTITION p20120811 START ('2012-08-11'::date) END ('2012-08-12'::date) WITH (tablename='tb1_partition_range_yyyymmdd_1_prt_p20120811', orientation=row , appendonly=true, compresslevel=5 ),           PARTITION p20120812 START ('2012-08-12'::date) END ('2012-08-13'::date) WITH (tablename='tb1_partition_range_yyyymmdd_1_prt_p20120812', orientation=row , appendonly=true, compresslevel=5 )          );ALTER TABLE public.tb1_partition_range_yyyymmdd OWNER TO gpadmin;---- Name: idx_yyyymmdd; Type: INDEX; Schema: public; Owner: gpadmin; Tablespace: --CREATE INDEX idx_yyyymmdd ON tb1_partition_range_yyyymmdd USING btree (yyyymmdd);---- Greenplum Database database dump complete--

还有一种方法就是\d table_name查看。这个只能查看字段信息啥的。

testdb=# \d+ tb1_partition_range_yyyymmddAppend-Only Table "public.tb1_partition_range_yyyymmdd"  Column  |  Type   | Modifiers | Storage | Description ----------+---------+-----------+---------+------------- id       | numeric |           | main    |  yyyymmdd | date    |           | plain   | Compression Type: zlibCompression Level: 5Block Size: 32768Checksum: tIndexes:    "idx_yyyymmdd" btree (yyyymmdd)Child tables: tb1_partition_range_yyyymmdd_1_prt_p20120811,              tb1_partition_range_yyyymmdd_1_prt_p20120812Has OIDs: noOptions: appendonly=true, compresslevel=5Distributed by: (id)Partition by: (yyyymmdd)testdb=#

总体来说还是不太方便，下面创建一个自定义的函数进行查看：

1. 创建语言

CREATE PROCEDURAL LANGUAGE plpythonu;

2. 创建函数（代码如下）：

vim get_table_structure.sql

create or replace function get_table_structure(tablename text)    returns textas $$    try:        table_name = tablename.lower().split('.')[1]        talbe_schema=tablename.lower().split('.')[0]    except (IndexError):        return 'Please in put "tableschema.table_name"'    get_table_oid="select oid,reloptions,relkind from pg_class where oid='%s'::regclass"%(tablename)    try:        rv_oid=plpy.execute(get_table_oid,5)        if not rv_oid:            return 'Did not find any relation named"'+tablename +'".'    except (Error):        return 'Did not find any relation named"'+tablename +'".'    table_oid=rv_oid[0]['oid']    rv_reloptions=rv_oid[0]['reloptions']    rv_relkind=rv_oid[0]['relkind']    create_sql="";    table_kind='table';    if rv_relkind !='r' and rv_relkind !='v':        plpy.error('%s is not table or view'%(tablename));    elif rv_relkind=='v':        get_view_def="select pg_get_viewdef(%s,'t') as viewdef;" % (table_oid)        rv_viewdef=plpy.execute(get_view_def);        create_sql='create view %s as \n' % (tablename)        create_sql += rv_viewdef[0]['viewdef']+'\n';        table_kind='view'    else:        get_columns="select a.attname,pg_catalog.format_type(a.atttypid,a.atttypmod),\       (select substring(pg_catalog.pg_get_expr(d.adbin,d.adrelid) for 128) \        from pg_catalog.pg_attrdef d where d.adrelid=a.attrelid and d.adnum=a.attnum and a.atthasdef) \        as default,a.attnotnull as isnull from pg_catalog.pg_attribute \        a where a.attrelid= %s and a.attnum >0 and not a.attisdropped order by a.attnum;" % (table_oid);        rv_columns=plpy.execute(get_columns)                    get_table_distribution1="select attrnums from pg_catalog.gp_distribution_policy t where localoid = '" + table_oid + "' "        rv_distribution1=plpy.execute(get_table_distribution1,500)        rv_distribution2=''        if rv_distribution1 and rv_distribution1[0]['attrnums']:            get_table_distribution2="select attname from pg_attribute where attrelid='"+table_oid+"' and attnum in (" + str(rv_distribution1[0]['attrnums']).strip('{').strip('}').strip('[').strip(']')+")"            rv_distribution2=plpy.execute(get_table_distribution2,500)            create_sql='create table %s (\n' % (tablename)        get_index="select pg_get_indexdef(indexrelid) as indexdef from pg_index where indrelid=%s" % (table_oid);        rv_index=plpy.execute(get_index);                get_parinfo1="select attname as columnname from pg_attribute where attnum =(select paratts[0] from pg_partition where parrelid=%s) and attrelid=%s;"%(table_oid,table_oid);        get_parinfo2=""" select pp.parrelid,prl.parchildrelid,case when pp.parkind='h'::"char" then 'hash'::text when pp.parkind='r'::"char" then 'range'::text when pp.parkind='l'::"char" then 'list'::text else null::text end as partitiontype,pg_get_partition_rule_def(prl.oid,true) as partitionboundary from pg_partition pp,pg_partition_rule prl where pp.paristemplate=false and pp.parrelid = %s and prl.paroid = pp.oid order by prl.parname; """ % (table_oid)        v_par_parent=plpy.execute(get_parinfo1);        v_par_info=plpy.execute(get_parinfo2);        max_column_len=10        max_type_len=4        max_modifiers_len=4        max_default_len=4        for i in rv_columns:            if i['attname']:                if max_column_len < i['attname'].__len__():                    max_column_len=i['attname'].__len__()            if i['format_type']:                if max_type_len < i['format_type'].__len__():                    max_type_len=i['format_type'].__len__()            if i['default']:                if max_type_len < i['default'].__len__():                    max_default_len=i['default'].__len__()        first=True        for i in rv_columns:            if first==True:                split_char=' ';                first=False            else:                split_char=',';            if i['attname']:                create_sql += " " + split_char + i['attname'].ljust(max_column_len+6)+''            else:                create_sql += "" + split_char + ' '.ljust(max_column_len+6)            if i['format_type']:                create_sql += ' ' + i['format_type'].ljust(max_type_len +2)            else:                create_sql += ' ' + ' '.ljust(max_type_len+2)            if i['isnull'] and i['isnull']:                create_sql += ' ' + ' not null '.ljust(8)            if i['default']:                create_sql += ' default ' + i['default'].ljust(max_default_len+6)            create_sql += "\n"        create_sql += ")"         if rv_reloptions:            create_sql +=" with ("+str(rv_reloptions).strip('{').strip('}').strip('[').strip(']') +")\n"            create_sql = create_sql.replace("'",'')        if rv_distribution2:            create_sql += 'Distributed by ('            for i in rv_distribution2:                create_sql += i['attname'] + ','            create_sql =create_sql.strip(',')+')'        elif rv_distribution1:            create_sql += 'Distributed randomly\n'        if v_par_parent:            partitiontype=v_par_info[0]['partitiontype'];            create_sql +='\nPARTITION BY '+ partitiontype + "("+v_par_parent[0]['columnname']+")\n(\n";            for i in v_par_info:                create_sql +=" " +i['partitionboundary']+',\n';            create_sql=create_sql.strip(',\n');            create_sql+="\n)"        create_sql+=";\n\n"        for i in rv_index:            create_sql += i['indexdef']+';\n'                get_table_comment="select 'comment on %s %s is '''|| COALESCE (description,'')|| '''' as comment from pg_description where objoid=%s and objsubid=0;" % (table_kind,tablename,table_oid)        get_column_comment="select 'comment on column %s.'||b.attname ||' is ''' || COALESCE(a.description,'')|| ''' ' as comment from pg_catalog.pg_description a,pg_catalog.pg_attribute b where objoid=%s and a.objoid=b.attrelid and a.objsubid=b.attnum;" % (tablename,table_oid)        rv_table_comment=plpy.execute(get_table_comment);        rv_column_comment=plpy.execute(get_column_comment);        for i in rv_table_comment:            create_sql += i['comment']+';\n'        for i in rv_column_comment:            create_sql +=i['comment']+';\n'        return create_sql;$$ LANGUAGE plpythonu;

3. 进行测试

testdb=# SELECT get_table_structure('public.tb1_partition_range_yyyymmdd');                                                get_table_structure                                                ------------------------------------------------------------------------------------------------------------------- create table public.tb1_partition_range_yyyymmdd (                                                                   id               numeric                                                                                          ,yyyymmdd         date                                                                                            ) with (appendonly=true, compresslevel=5)                                                                          Distributed by (id)                                                                                                PARTITION BY range(yyyymmdd)                                                                                       (                                                                                                                   PARTITION p20120811 START ('2012-08-11'::date) END ('2012-08-12'::date) WITH (appendonly=true, compresslevel=5),   PARTITION p20120812 START ('2012-08-12'::date) END ('2012-08-13'::date) WITH (appendonly=true, compresslevel=5)   );                                                                                                                                                                                                                                    CREATE INDEX idx_yyyymmdd ON tb1_partition_range_yyyymmdd USING btree (yyyymmdd);                                  原文出处：http://www.cnblogs.com/gomysql/p/6007013.html