S3Report

S3Report is a REST method handler for data analysis.

Functionality

S3Report can generate contingency tables (a.k.a. pivot tables) from S3Resources.

Dependencies

S3Report uses ​pyvttbl to generate contingency tables. A modified version of pyvttbl is integrated into the S3 framework.

Pyvttbl requires the following Python modules:

• numpy
• matplotlib

Caveats

S3Report supports grouping and aggregation by virtual fields - however, using this without care can lead to severe scalability problems:

With large numbers of records involved it can take a long time to compute all virtual field values - and especially where this involves additional database lookups it may quickly exhaust any available bandwidth. Example calculation:

Records in the table	Number of virtual fields with DB lookups	Concurrent users	Total number of queries
1,000	1	1	1,001
1,000	5	1	5,001
30,000	5	1	150,001
30,000	5	5	750,005
30,000	5	100	15,000,100

Unless you're running on a super-computer, such a scenario would take your site beyond any reasonable response times - and users may end up waiting forever to get their report (make sure your site has a reasonable timeout for requests).

Without virtual fields, you have a very different scenario:

Records in the table	Number of virtual fields with DB lookups	Concurrent users	Total number of queries
1.000	0	1	1
30,000	0	100	100

Therefore, it is strongly recommended to minimize (better: avoid) the use of virtual fields which include additional DB lookup as rows, cols or fact parameter in reports wherever large numbers of records can be expected.

URL Methods

S3Report responds to the /report URL method, for all resources (generic method).

The following parameters are accepted:

Parameter	Explanation	required?
rows	the name of the field to be used for the table rows	yes
cols	the name of the field to be used for the table columns	no (if no cols are specified, all instance values appear in 1 column)
fact	the name of the field to be used for the instance values	no (falls back to "name" if present, otherwise to "id")
aggregate	the aggregation function	no (default: list)
table	whether to hide the pivot table (table=0) or show it (table=1)	no
chart	render as chart by default, format: chart=<type>:<dimension>	no

rows, cols and fact support the same options as list_fields:

• fields in the table
• virtual fields in the table
• fields/virtual fields in tables linked by foreign keys ($-notation)

The chart option accepts:

• type: piechart|barchart|breakdown
• dimension: rows|cols

S3Report supports a number of aggregation functions. The following functions have been tested so far:

Function	Explanation
list	a comma-separated list of all instance values
count	the number of instance values
sum	the sum of all instance values
avg	the average (mean) of all instance values

Examples

• ​http://localhost:8000/eden/org/organisation/report?rows=country&cols=sector_id&fact=name
• ​http://localhost:8000/eden/pr/person/report?rows=age_group&cols=gender&fact=id&aggregate=count

$-notation for references:

• ​http://localhost:8000/eden/org/office/report?rows=location_id$parent&cols=type&fact=name

reduced parameter list:

• ​http://localhost:8000/eden/org/office/report?rows=type&aggregate=count
• ​http://localhost:8000/eden/org/organisation/report?rows=sector_id

Report Options

Table configurations can contain a report_options item, which is a Storage object. This object is used to configure reports and report options form.

The rows, cols, facts and aggregate items are lists of available values for the user to select from.

The defaults property is a Storage object that contains the default values for the report. It can contain a value for rows, cols, fact, aggregate and totals (as described in URL Methods).

The search property is a list of S3Search widgets that will allow the report to be filtered. If no search property is specified, no filter form will be available.

Here is an example of a report_options item:

report_options=Storage(
        rows=report_fields,
        cols=report_fields,
        fact=report_fields,
        defaults=Storage(
                rows="project_id",
                cols="name",
                fact="time_actual",
                aggregate="sum",
                totals=True
        ),
        search=[
                S3SearchOptionsWidget(
                        name="project_id",
                        label = T("Project"),
                        field = "project_id",
                ),
        ],
)

All items in report_options and defaults are optional.

If fact and methods are configured like:

   report_options = Storage(
       fact = [field1, field2, field3],
       methods = [method1, method2],
       ...
   )

then S3Report will automatically provide a selection of all (mathematically) meaningful field-method-combinations. Some of these combinations may not be relevant for the use-case, though. To specify field-method-combinations instead, you can configure it like:

   report_options = Storage(
       fact = [
               (field1, method1),
               (field2, method1),
               (field2, method2),
               (field3, method1),
              ],
       ...
   )

Optionally, you can define a custom label for each combination (which will be used in the select list):

   report_options = Storage(
       fact = [
               (field1, method1, T("My Report A")),
               (field2, method1, T("My Report B")),
               (field2, method2, T("My Report C")),
               (field3, method1, T("My Report D")),
              ],
       ...
   )

Of course, you can also specify custom labels for the fields where required:

   report_options = Storage(
       fact = [
               ((T("My Label For Field1"), field1), method1, T("My Report A")),
               (field2, method1, T("My Report B")),
               (field2, method2, T("My Report C")),
               (field3, method1, T("My Report D")),
              ],
       ...
   )

Further Development

The following enhancements are currently under development:

• Support for JSON, CSV and XLS exports