Apache Hawq-使用中遇到的問題和解決方法

\df 查看函數列表
\df+ 查看自定義函數

\dc 查看轉換
\dc+

\l 查看數據庫列表

\d table 查看表信息
\d+ table 查看表詳細信息

select * from information_schema.schemata;

1. HAWQ空值問題:
   HAWQ導入數據時，默認情況下空值必須使用"\N"來表示

2.hawq load導入csv數據時，數據文件200G，啟用一個gpfdist節點，花費時間1個小時40分鐘，報錯。
原因可能是內存不足。

drop table t1;
create table t1(id int, mac varchar(20), year int) 
with (appendonly=true,orientation=parquet,compresstype=snappy, bucketnum=18)
distributed by(mac)
PARTITION BY RANGE (year)
( START (2001)INCLUSIVE END (2003)EXCLUSIVE EVERY (1),
  DEFAULT PARTITION extra );

```

ALTER TABLE t1 SPLIT DEFAULT PARTITION
START (2003) INCLUSIVE
END (2004) EXCLUSIVE
INTO (PARTITION y2003, default partition);

報錯：

NOTICE: exchanged partition "extra" of relation "t1" with relation "pg_temp_689110"
NOTICE: dropped partition "extra" for relation "t1"
ERROR: bucketnum requires a numeric value

解決方法： 去掉指定的bucketnum

set default_hash_table_bucket_number=9;
drop table t1;
create table t1(id int, mac varchar(20), year int)
with (appendonly=true,orientation=parquet,compresstype=snappy)
distributed by(mac)
PARTITION BY RANGE (year)
( START (2001)INCLUSIVE END (2003)EXCLUSIVE EVERY (1),
DEFAULT PARTITION extra );

ALTER TABLE t1 SPLIT DEFAULT PARTITION
START (2003) INCLUSIVE
END (2004) EXCLUSIVE
INTO (PARTITION y2003, default partition);
set default_hash_table_bucket_number=18;