增加列
可以使用 addColumn 函数给分布式数据库中的表增加新的列。
$ ID=1..6
$ x=1..6\5
$ t1=table(ID, x)
$ db=database("dfs://rangedb",RANGE, 1 4 7)
$ pt = db.createPartitionedTable(t1, `pt, `ID)
$ pt.append!(t1);
$ addColumn(pt,["price", "qty"],[DOUBLE, INT]);
增加列后,在插入新结构数据之前,仍然可以插入原来结构的数据。
$ t2=table(1 as ID, 1.2 as x)
$ pt.append!(t2)
$ select * from pt;
ID |
x |
price |
qty |
---|---|---|---|
1 |
0.2 |
||
2 |
0.4 |
||
3 |
0.6 |
||
1 |
1.2 |
||
4 |
0.8 |
||
5 |
1 |
||
6 |
1.2 |
一旦插入了新结构的数据,就不能插入原来结构的数据。
$ t3=table(1 as ID, 1.6 as x, 10.0 as price, 6 as qty)
$ pt.append!(t3)
$ select * from pt;
ID |
x |
price |
qty |
---|---|---|---|
1 |
0.2 |
||
2 |
0.4 |
||
3 |
0.6 |
||
1 |
1.2 |
||
1 |
1.6 |
10 |
6 |
4 |
0.8 |
||
5 |
1 |
||
6 |
1.2 |
$ t4=table(2 as ID, 2.2 as x)
$ pt.append!(t4);
The data to append contains fewer columns than the schema.