> On Sept. 29, 2014, 12:56 a.m., Matthew Hayes wrote: > > datafu-pig/src/main/java/datafu/pig/util/SelectFieldByName.java, line 49 > > <https://reviews.apache.org/r/25564/diff/2/?file=707974#file707974line49> > > > > Hmm, something just occurred to me. This does not currently provide > > the output schema. So this is one problem. But, how do we determine the > > output schema? If the output value is decided dynamically, then it can > > vary. One way to address this is to require that all the other values of > > the tuple are of the same type. Then you just take the schema form the > > first value. In your example they are all chararray. But this does limit > > the uses of this UDF. > > Russell Jurney wrote: > In practice, this is not an issue. The UDF is used this way, and you can > cast it to what you want. > > with_value_substitution = FOREACH with_group GENERATE > FLATTEN(ChooseFieldByValue(groupField, *)) AS groupValue:chararray, > *, > (int)$period AS periodSeconds:int; > > However, I don't see why I can't detect the schema of the field selected > and return that?
The schema can't be dynamic like that. I'll have to think about this some more. I don't like that we have to cast it like this. One way we can make this better is to have the UDF pick the schema that is best fit for the types provided. For example, if all the fields are of the same type, like chararray, then the resulting type is chararray. Otherwise make the type bytearray and you can cast however you want. I'd like to hear what other people think about this. How about emailing datafu dev? - Matthew ----------------------------------------------------------- This is an automatically generated e-mail. To reply, visit: https://reviews.apache.org/r/25564/#review54788 ----------------------------------------------------------- On Sept. 29, 2014, 12:20 a.m., Russell Jurney wrote: > > ----------------------------------------------------------- > This is an automatically generated e-mail. To reply, visit: > https://reviews.apache.org/r/25564/ > ----------------------------------------------------------- > > (Updated Sept. 29, 2014, 12:20 a.m.) > > > Review request for DataFu, Jonathan Coveney, Jakob Homan, Matthew Hayes, and > Sam Shah. > > > Repository: datafu > > > Description > ------- > > Example use: > group_fields = LOAD '/e8/smalldata/group_fields.txt' AS > (groupField:chararray); > with_group = CROSS group_fields, hour_rounded; > with_group = FOREACH with_group GENERATE group_fields::groupField AS > groupField, > hour_rounded::sourceNameOrIp AS sourceNameOrIp, > hour_rounded::destinationNameOrIp AS destinationNameOrIp, > ...; > with_value_substitution = FOREACH with_group GENERATE > ChooseFieldByValue(groupField, *) AS groupValue:tuple(value:chararray), *; > with_value_substitution = FOREACH with_value_substitution GENERATE > FLATTEN(groupValue) AS groupValue:chararray, > groupField, > foo, > bar, > ...; > all_success = FOREACH (GROUP with_value_substitution BY (groupField, > groupValue, day)) GENERATE > FLATTEN(group) AS (seriesType, groupValue, day), > (int)COUNT_STAR(with_value_substitution) AS connections:int; > > > Diffs > ----- > > datafu-pig/src/main/java/datafu/pig/util/SelectFieldByName.java > PRE-CREATION > datafu-pig/src/test/java/datafu/test/pig/util/SelectFieldByNameTest.java > PRE-CREATION > > Diff: https://reviews.apache.org/r/25564/diff/ > > > Testing > ------- > > This UDF was used to replace a very inefficient pig script where macros that > did many individual GROUP BY's took many minutes to plan. > > Testing: unit tests and used on real data on a cluster. > > > Thanks, > > Russell Jurney > >
