Feature Proposal: Query Syntax in SEARCH Format

Motivation

Ability to use query syntax to format meta data, such as attachments.

Description and Documentation

TWiki already has a QuerySearch for VarSEARCH of type="query" and for VarIF (IfStatements). Being able to use the same query language to format the output is a logical enhancement.

The FormattedSearch has variables to render meta data, such as $formfield(), $rev(), $parent(). A new $query() variable is proposed to format any meta data available in the QuerySearch.

Examples

1. Access file comments:

Assuming the current page has a file attachment called mugshot.jpg. It is possible to get the file comment of with the following query:

%SEARCH{ "form.name='UserForm'" type="query" nonoise="on" format="   * $topic: $query(attachments[name='mugshot.jpg'].comment)" }%

This returns a bullet list with topic name and file comment of mugshot.jpg (if any).

2. Access file size:

Return the size of all .gif files attached to the current page:

%SEARCH{ "%TOPIC%" scope="topic" nonoise="on" format="$query(attachments[name~'*.gif'].size)" }%

This returns an array of file sizes, such as [625, 158] if multiple .gif files are attached, or an integer if a single file is attached.

Impact

Implementation

-- Contributors: PeterThoeny - 2010-02-09

Discussion

Outstanding issue: The query syntax supports parenthesis. The format="..." syntax for variables is $variable(...). There is an ambiguity if the query contains parenthesis, such as $query(attachments[name ~ '*.png' AND date > d2n('2010-01-01').arraysize])=. How to solve that? Options:

1. Do nothing for initial implementation, e.g. live with limitation that parenthesis cannot be used inside a $query() variable.

2. Parse properly, e.g. keep track of number of opening and closing parenthesis. This is expensive at runtime.

3. Require to escape parenthesis inside $query(), such as $query(attachments[name ~ '*.png' AND date >= d2n\('2010-01-01'\).arraysize])

4. Introduce an end token, such as $query(...#end). This is easy to implement, but is not so intuitive and looks ugly.

I favor number 1 or 3. Opinions?

-- PeterThoeny - 2010-02-09

Looks good proposal - i support this.

-- SopanShewale - 2010-02-10

I checked in the initial code and doc. For now it is 1 (do not support parenthesis in query). Doc is at http://develop.twiki.org/~twiki4/cgi-bin/view/TWiki/FormattedSearch - see $query(query-syntax)

-- PeterThoeny - 2010-02-16