Hi Gimantha,
On Thu, Mar 17, 2016 at 9:05 PM, Gimantha Bandara <[email protected]> wrote:
> Hi all,
>
> DAS 3.0.0 and DAS 3.0.1 has 5 built-in Aggregates[1][2] namely MIN, MAX,
> SUM, AVG and COUNT which can be used in interactive analytics. Sometimes
> some scenarios may require custom aggregate functions for aggregate
> calculations. For this we have introduced a new interface from
> carbon-analytics/analytics-core, which has three methods which need to be
> implemented.
>
> Interface :
> org.wso2.carbon.analytics.dataservice.core.indexing.aggregates.AggregateFunction
>
> Following are the three methods that need to be implemented.
>
> *public void process(RecordValuesContext ctx, String[] aggregateFields)
> throws AnalyticsException*;
>
> This method will get called for all the records which need to be
> aggregated. RecordValuesContext will contain the record values of the
> current record being processed. aggregateFields will contain an array of
> fields which will be used for the aggregation. The order of the
> aggregateFields will matter when we implement the logic. For example, lets
> say we are going to implement SUM aggregate. Then we know that only one
> field will be required to calculate SUM and always aggregateFields will
> contain one field name in it, which is the name of the field being SUMed.
>
> public void process(RecordValuesContext ctx, String[] aggregateFields)
> throws AnalyticsException {
> if (aggregateFields == null || aggregateFields.length == 0) {
> throw new AnalyticsException("Field to be aggregated, is
> missing");
> }
> Object value = ctx.getValue(aggregateFields[0]);
> if (value == null) {
> throw new AnalyticsException("Error while calculating SUM:
> value of the field, " +
> aggregateFields[0] + " is null");
> }
> if (value instanceof Number) {
> sum += ((Number)value).doubleValue();
> } else {
> throw new AnalyticsException("Error while calculating Average:
> Value '" + value.toString() +
> "', being aggregated is not
> numeric.");
> }
> }
>
>
What are the other details the RecordValueContext has? Is it only having
the values for the fields to be aggregated? If so, I think we can simple
have Map for this as key, value pair right? I cannot think of a case where
the aggregate function is based some different field than the field which
needs to be aggregated. Sorry, if I'm missing something..
Thanks,
Sinthuja.
>
>
>
> *public Object finish() throws AnalyticsException*
> Once the aggregation is complete for a group or for whole record set, this
> method will be called. This will return the final result of the aggregate
> function. for example, the SUM aggregate,
>
> public Number finish() throws AnalyticsException {
> return sum;
> }
>
>
>
> *public String getAggregateName()*
> This method is used to identify the Aggregate function uniquely among
> other Aggregate functions. You can return a preferred string inside this
> method.
>
> *Calling custom aggregate functions through Javascript API*
>
> var queryInfo = {
> tableName:"Students", //table name on which the aggregation is
> performed
> searchParams : {
> groupByField:"location", //grouping field if any
> query : "Grade:10" //additional filtering query
> aggregateFields:[
> {
> fields:["Height", "Weight"], //fields necessary for aggregate
> function
> aggregate:"CUSTOM_AGGREGATE", //unique name of the aggregate
> function, this is what we return using "getAggregateName" method above.
> alias:"aggregated_result" //Alias for the result of the
> aggregate function
> }]
> }
> }
>
> client.searchWithAggregates(queryInfo, function(data) {
> console.log (data["message"]);
> }, function(error) {
> console.log("error occured: " + error["message"]);
> });
>
>
> *Note that the order elements in attribute "fields" will be the same
> order of aggregateFields parameter's element order in above process method.
> That is Height will be aggregateFields[0] and Weight will be
> aggregateFields[1] in process method. Based on that order,
> "CUSTOM_AGGREGATE" should be implemented.*
>
>
>
> *Aggregates REST APIs*This is as same as the Javascript API.
>
> POST https://localhost:9443/analytics/aggregates
> {
> "tableName":"Students",
> "groupByField":"location",
> "aggregateFields":[
> {
> "fields":["Height", "Weight"],
> "aggregate":"CUSTOM_AGGREGATE",
> "alias":"aggregated_result"
> }]
> }
>
> [1]
> https://docs.wso2.com/display/DAS301/Retrieving+Aggregated+Values+of+Given+Records+via+REST+API
> [2]
> https://docs.wso2.com/display/DAS301/Retrieving+Aggregated+Values+of+Given+Records+via+JS+API
> --
> Gimantha Bandara
> Software Engineer
> WSO2. Inc : http://wso2.com
> Mobile : +94714961919
>
> _______________________________________________
> Architecture mailing list
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>
>
--
*Sinthuja Rajendran*
Associate Technical Lead
WSO2, Inc.:http://wso2.com
Blog: http://sinthu-rajan.blogspot.com/
Mobile: +94774273955
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