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The above expression reach into the database for all Consultants, takes the active assignments, sums the BilledHours that has been reported after vTheStartDate and returns a list of tuples of type {Assignment,Consultant,Part1} where part1 will be the sum of hours. | The above expression reach into the database for all Consultants, takes the active assignments, sums the BilledHours that has been reported after vTheStartDate and returns a list of tuples of type {Assignment,Consultant,Part1} where part1 will be the sum of hours. | ||
'''Note on limitations''': OCL is a more expressive language than SQL. This leads to situations where something that is easy to express in ocl MAY not be correctly translated to a equivalent SQL-statement. We know that performing multiple aggregating functions like sum,min,max,avg,count(*) (in ocl it will be ->[[OCLOperators minValue|minvalue]], ->[[OCLOperators maxValue|maxvalue]], ->average, ->[[OCLOperators size|size]]) in the same tuple for different sets of data will not yield the expected results. Always do a sanity check of the numbers returned from a new expression and test it to verify its efficacy. Example of expression given wrong answer: ->collect(x|x,x.Name,x.Something->select(goodone).Value->sum,x.Something->select(badone).Value->sum ) , workaround - split it in two, one expression per aggregation, | '''Note on limitations''': OCL is a more expressive language than SQL. This leads to situations where something that is easy to express in ocl MAY not be correctly translated to a equivalent SQL-statement. We know that performing multiple aggregating functions like sum,min,max,avg,count(*) (in ocl it will be ->[[OCLOperators minValue|minvalue]], ->[[OCLOperators maxValue|maxvalue]], ->[[OCLOperators average|average]], ->[[OCLOperators size|size]]) in the same tuple for different sets of data will not yield the expected results. Always do a sanity check of the numbers returned from a new expression and test it to verify its efficacy. Example of expression given wrong answer: ->collect(x|x,x.Name,x.Something->select(goodone).Value->sum,x.Something->select(badone).Value->sum ) , workaround - split it in two, one expression per aggregation, | ||
Always remember that your SQL-server might also need indexes and other performance settings to execute your expression efficiently. | Always remember that your SQL-server might also need indexes and other performance settings to execute your expression efficiently. | ||
See also: [[OCLOperators Sqlpassthrough|Sqlpassthrough]], [[OCLOperators PSEvalValue|PSEvalValue]], [[OCLOperators PSEval|PSEval]] | See also: [[OCLOperators Sqlpassthrough|Sqlpassthrough]], [[OCLOperators PSEvalValue|PSEvalValue]], [[OCLOperators PSEval|PSEval]] | ||
Revision as of 11:05, 5 June 2023
Makes it possible to use oclPS in any OCL expression. Using this, you can "reach into" the database from OCL and action-language (EAL).
Expression template:
SomeClass.PSEvalTuples(<ps-expression>,maxfetch,offset,<dependon>)
Note! - PSEvalTuples doesn't subscribe on sets from DB. To make the operator auto-updating, provide an expression in "dependon" that, when changed, should also rerun the PSEvalTuples expression. This can, for example, be a timer.
Example:
Consultant.PSEvalTuples(self.Assignments->select(a|a.Active)->collect(a|a,a.Consultant,a.BilledHours->select(bh|bh.WorkDate>vTheStartDate).Hours->sum), 100, 0, vTheStartDate)
The result type is a Tuple.
The above expression reach into the database for all Consultants, takes the active assignments, sums the BilledHours that has been reported after vTheStartDate and returns a list of tuples of type {Assignment,Consultant,Part1} where part1 will be the sum of hours.
Note on limitations: OCL is a more expressive language than SQL. This leads to situations where something that is easy to express in ocl MAY not be correctly translated to a equivalent SQL-statement. We know that performing multiple aggregating functions like sum,min,max,avg,count(*) (in ocl it will be ->minvalue, ->maxvalue, ->average, ->size) in the same tuple for different sets of data will not yield the expected results. Always do a sanity check of the numbers returned from a new expression and test it to verify its efficacy. Example of expression given wrong answer: ->collect(x|x,x.Name,x.Something->select(goodone).Value->sum,x.Something->select(badone).Value->sum ) , workaround - split it in two, one expression per aggregation,
Always remember that your SQL-server might also need indexes and other performance settings to execute your expression efficiently.
See also: Sqlpassthrough, PSEvalValue, PSEval