SID-01721: Problem with SEARCH in nested FOREACH

Status:	Answered	TWiki version:	5.0.1	Perl version:
Category:	ForEachPlugin	Server OS:	Sun	Last update:	12 years ago

I've boiled my problem down to the following construct:

%FOREACH{"feature" in="A, B, C"}%

%FOREACH{"kind" in="X, Y, Z"}% 

$percntSEARCH{ "parent.name = 'UseCasesUnderReview' AND Feature = '$feature' AND Kind = '$kind'" type="query"}$percnt 

%NEXT{"kind"}%

%NEXT{"feature"}%

My search returns no results, although I have topics that match the query (Feature and Kind are form fields). The query string that displays in the results is correct.

Searched: parent.name = 'UseCasesUnderReview' AND Feature = 'A' AND Kind = 'X'

If I change my search's query string to substitute a constant for the $kind variable like so:

$percntSEARCH{ "parent.name = 'UseCasesUnderReview' AND Feature = '$feature' AND Kind = 'X'" type="query"}$percnt

The query gets the results I expect. The query string displayed in the result is identical to the first case which fails. If I swap the nesting around so feature is the inner loop and kind is the outer loop the problem moves from the substitution of $kind to the substitution of $feature.

Hoping someone can point out the error of my ways here.

-- John Weber - 2013-06-05

Discussion and Answer

I've been experimenting with this further and decided I really don't know how escapes and variable substitution work. I've developed this simpler example using FOREACH and CALC

| *Feature* | *Kind* |
%FOREACH{"feature" in="A, B2, C33"}% 
$percntFOREACH{"kind" in="X, Y2, Z33"}$percnt 
$percntCALCULATE{| $feature ($LENGTH($feature)) | $kind ($LENGTH($kind)) |}$percnt 
$percntNEXT{"kind"}$percnt 
%NEXT{"feature"}%

The values in the feature column display as I would expect and their reported length matches the length of the value. For the kind column, the values display as I expect but the length is always reported as 5 which is the length of the string $kind. How can I get the values from the FOREACH inner and outer variables to be evaluated consistently inside the CALCULATE?

-- John Weber - 2013-06-11

I don't use the FOREACH so I can't give you advise. One thing strikes me though that you will have a very poor performance because the SEARCH will be done repeatedly. Consider doing just one search. You could do a query search with many AND and OR, or you could use a regular expression search. Untested example:

%SEARCH{
 "META:TOPICPARENT.name.UseCasesUnderReview;META:FIELD.name=.Feature.*value=.(A|B2|C33);META:FIELD.name=.Kind.*value=.(X|Y2|Z33)"
 type="regex"
}%

Details in VarSEARCH, RegularExpression.

-- Peter Thoeny - 2013-06-18

Thanks for the suggestion. The problem is not really about search and more about how escapes are evaluated when you have nested variables like in my example. Experimenting further I came up with an example that works as I would like, but I had to create two topics:

Topic NestedForNext

| *Feature* | *Kind* |
%FOREACH{"feature" in="A, B2, C33"}% 
$percntINCLUDE{"FeatureTable" FEATURE="$feature"}$percnt 
%NEXT{"feature"}% 

Topic FeatureTable

%FOREACH{"kind" in="X, Y2, Z33"}% 
$percntCALCULATE{| %FEATURE% ($LENGTH(%FEATURE%)) | $kind ($LENGTH($kind)) |}$percnt 
%NEXT{"kind"}% 

When I tried to combine this into a single topic like so:

| *Feature* | *Kind* |
%FOREACH{"feature" in="A, B2, C33"}% 
$percntFOREACH{"kind" in="X, Y2, Z33"}$percnt 
$percntCALCULATE{| $feature ($LENGTH($feature)) | $kind ($LENGTH($kind)) |}$percnt 
$percntNEXT{"kind"}$percnt 
%NEXT{"feature"}% 

The length of the value in the Kind column is always reported as 5 which is the length of the string '$kind' even though I see the correct values for $kind displayed in the column.

If FOREACH is the problem, is there a better way to do what I'm trying to do here which doesn't require FOREACH?

-- John Weber - 2013-06-20

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