transDS!

Syntax

transDS!(ds, tranFunc)

Arguments

ds is a data source or a list of data sources. It is the sole argument of all the functions in transFunc.

tranFunc is a function to be applied to ds.

Details

Apply data transforming functions to a data source or a list of data sources.

Examples

In the following example, the data type of column trade_time from the DFS table trades1 is converted into NANOTIMESTAMP and inserted into the DFS table trades2.

$ db=database("dfs://stock1",VALUE,`A`B`C`D)
$ n=200000
$ trade_time=2018.01.02T06:12:03.458+1..n
$ sym=rand(`A`B`C`D,n)
$ qty=rand(100.0,n)
$ price=rand(100.0,n)
$ t=table(trade_time,sym,qty,price)
$ trades1=db.createPartitionedTable(t,`trades1,`sym).append!(t);

$ ds=sqlDS(<select * from trades1>);

$ def convertNanotimestamp(t){
$    return select nanotimestamp(trade_time), sym, qty, price from t
$ }

$ ds.transDS!(convertNanotimestamp);

$ db=database("dfs://stock2",VALUE,`A`B`C`D)
$ t=table(1:0,`trade_time`sym`qty`price,[NANOTIMESTAMP,SYMBOL,DOUBLE,DOUBLE])
$ trades2=db.createPartitionedTable(t,`trades2,`sym);

$ mr(ds,append!{trades2},,,false);

$ exec count(*) from trades2;
200000