S3ResourceFilter

S3ResourceFilter is a class representing the DAL queries and Python filters to select the records for a resource.

Overview

S3ResourceFilters are a part of S3Resources:

They contain the queries and filters to extract the data from the database.

At the time an S3Resource gets defined, a S3ResourceFilter is automatically added to it. This default filter (so called "master query") covers:

• available records (i.e. not deleted)
• accessible records (i.e. access permitted)
• selected records by record ID and/or UID
• joined records (e.g. components)

It is possible to extend this filter during the request:

• by a URL query
• by the S3Resource.add_filter() method

S3ResourceFilters can filter for both real fields in the database table as well as virtual (computed) fields.

Design

S3ResourceFilters consist of a hierarchical set of web2py Query and S3ResourceQuery objects, where:

• Query instances represent the DAL queries ("query")
• S3ResourceQuery instances represent virtual field filters ("vfltr")

The process for the extraction of rows from the database is as follows: