Query Search

Query searches help you search the contents of forms attached to your topics, as well as the values of other meta-data attached to the topic. Using query searches you can search:

  1. The fields of forms
  2. Parent relationships
  3. File attachment information (but not the attached files themselves)

Query searches are defined using a simple SQL-like query language. The language consists of field specifiers and constants joined with operators.

Field specifiers

You use field specifiers to say what value from the topic you are interested in.

All meta-data in a topic is referenced according to a simple plan.

  • name - name of the topic
  • web - name of the web the topic is within
  • text - the body text of the topic
  • META:FILEATTACHMENT
    • arraysize
    • for each attachment
      • name
      • attr
      • path
      • size
      • user
      • rev
      • date
      • comment
  • META:TOPICPARENT
    • name
  • META:TOPICINFO
    • author
    • date
    • format
    • rev - topic revision (12) to match %REVINFO{'$rev'}% and FormattedSearch $rev
    • version - internal Store topic version (1.12 for rcs based Stores)
  • META:TOPICMOVED
    • by
    • date
    • from
    • to
  • META:FORM - the main form of the topic
    • name (known as the formname)
  • META:FIELD - the fields in the form.
    • arraysize
    • for each field in the form
      • name
      • title
      • value
  • META:PREFERENCE
    • arraysize
    • for each preference in the topic
      • name
      • value

See TWikiMetaData for details of what all these entries mean.

Most things at the top level of the plan - META:TOPICPARENT, META:TOPICINFO etc - are structures which are indexed by keys. For example, META:TOPICINFO has 4 entries, which are indexed by the keys author, date, format and version. META:FILEATTACHMENT, META:FIELD and META:PREFERENCE are all arrays, which means they can have any number of records under them. Arrays are indexed by numbers - for example, the first entry in the META:FIELD array is entry 0. The field specifier arraysize returns the number of items in an array, for example, attachments.arraysize returns the number of attachments.

It's a bit clumsy having to type META:FILEATTACHMENT every time you want to refer to the array of attachments in a topic, so there are some predefined aliases that make it a bit less typing:

  • attachments means the same as META:FILEATTACHMENT
  • info means the same as META:TOPICINFO
  • parent means the same as META:TOPICPARENT
  • moved means the same as META:TOPICMOVED
  • form means the same as META:FORM
  • fields means the same as META:FIELD, You can also use the name of the form (the value of form.name e.g. PersonForm)
  • preferences means the same as META:PREFERENCE

This plan is referenced using a simple syntax:

Syntax Means Examples
X refers to the field named X. info, META:TOPICMOVED, attachments, name.
X.Y refers to the entry with the key Y in the structure named X info.date, moved.by, META:TOPICPARENT.name, attachments.arraysize
X[query] refers to all the elements of the array X that match query. If query is of the form name='Y' then you can use the same X.Y syntax as is used for accessing structures. attachments[size>1024], DocumentForm[name!='Summary' AND value~'top secret'].value, DocumentForm.Summary
X[N] where X is an array and N is an integer number >= 0, gets the Nth element of the array X attachments[3]
X/Y accesses Y from the topic specified by the value of X. X must evaluate to a topic name parent.name/(form.name='ExampleForm') will evaluate to true if (1) the topic has a parent, (2) the parent topic has the main form type ExampleForm.

Note: at some point TWiki may support multiple forms in the same topic. For this reason you are recommended not to use the fields shortcut when accessing form fields, but always use the name of the form instead.

There is a shortcut for accessing form fields. If you use the name of a field (for example, LastName) in the query without a . before it, that is taken to mean "the value of the field named this". This works if and only if the field name isn't the same as of the top level entry names or their aliases described above. For example, the following expressions will all evaluate to the same thing:

  • PersonForm[name='Lastname'].value
  • Lastname
  • PersonForm.Lastname
If X would conflict with the name of an entry or alias (e.g. it's moved or maybe parent), you can prepend the name of the form followed by a dot, as shown in the last example.

Constants

You use constants for the values that you compare with fields. Constants are either strings, or numbers. Strings are always delimited by single-quotes (you can escape a quote using backslash). Numbers can be any integer or floating point number. Constants can be supplied by TWikiVariables, such as '%TOPIC%' representing the current topic name.

Operators

Field specifiers and constants are combined using operators to create queries.

Operator Meaning
= Left-hand side (LHS) exactly matches the value on the Right-hand side (RHS). Numbers and strings can be compared.
!= Inverse of =.
~ wildcard match ('*' will match any number of characters, '?' will match any single character e.g. "PersonForm.Surname ~ '*Smit?'") Note: Surname ~ 'Smith' is the same as Surname = 'Smith'
< LHS is less that RHS. If both sides are numbers, the order is numeric. Otherwise it is alphabetic (applies to all comparison operators)
> >
>=
<=
lc(x) Converts x to lower case, Use for caseless comparisons.
uc(x) Converts x to UPPER CASE. Use for caseless comparisons.
d2n(x) Converts a date (expressed in one of the formats that TWiki can parse) to a number of seconds since 1st Jan 1970. This is the format dates are stored in inside TWiki, and you have to convert a string date using d2n before you can compare it with - for example - the date an attachment was uploaded. Times without a timezone are assumed to be in server local time. If you have date fields in your forms, note that they are not stored in TWiki's internal format, but are stored as text strings. You should still use d2n to convert them to numbers for comparisons, though.
NOT Invert the result of the subquery
AND Combine two subqueries
OR Combine two subqueries
() Bracketed subquery

IDEA! The same operators are supported for %IF statements.

Putting it all together

When a query is applied to a topic, the goal is to reduce to a TRUE or FALSE value that indicates whether the topic matches that query or not. If the query returns TRUE, then the topic is included in the search results.

A query matches if the query returns one or more values when it is applied to the topic. So if I have a very simple query, such as "attachments", then this will return TRUE for all topics that have one or more attachments. If I write "attachments[size>1024 AND name ~ '*.gif']" then it will return TRUE for all topics that have at least one attachment larger than 1024 bytes with a name ending in .gif.

Gotcha

  • Remember that in the query language, TWiki topic names are constants. You cannot write Main.JohnSmith/UserForm.FirstName because Main.JohnSmith will be interpreted as a form field name. If you want to refer to topics you must enclose the topic name in single quotes i.e. 'Main.JohnSmith'/UserForm.FirstName

Examples

Query examples

  • attachments[name='purdey.gif'] - true if there is an attachment call purdey.gif on the topic
  • attachments[name~'*.gif'].arraysize > 3 - true if there are at least 4 .gif files attached to the topic
  • (fields[name='Firstname'].value='Emma' OR fields[name='Firstname'].value='John') AND fields[name='Lastname'].value='Peel' - true for 'Emma Peel' and 'John Peel' but not 'Robert Peel' or 'Emma Thompson'
  • (Firstname='Emma' OR Firstname='John') AND Lastname='Peel' - shortcut form of the previous query
  • HistoryForm[name='Age'].value>2 - true if the topic has a HistoryForm, and the form has a field called Age with a value > 2
  • HistoryForm.Age > 2 - shortcut for the previous query
  • preferences[name='FaveColour' AND value='Tangerine'] - true if the topic has the given preference setting and value
  • Person/(ClothesForm[name='Headgear'].value ~ '*Bowler*' AND attachments[name~'*hat.gif' AND date < d2n('2007-01-01')]) - true if the form attached to the topic has a field called Person that has a value that is the name of a topic, and that topic contains the form ClothesForm, with a field called Headgear, and the value of that field contains the string 'Bowler', and the topic also has at least one attachment that has a name matching *hat.gif and a date before 1st Jan 2007. (Phew!)

Search examples

Find all topics that are children of this topic in the current web

%SEARCH{"parent.name = '%TOPIC%'" web="%WEB%" type="query"}%
Find all topics that have an attachment called 'grunge.gif'
%SEARCH{"attachments[name='grunge.gif']" type="query"}%
Find all topics that have form ColourForm where the form field 'Shades' is 'green' or 'yellow' but not 'brown'
%SEARCH{"(lc(Shades)='green' OR lc(Shades)='yellow') AND NOT(lc(Shades) ~ 'brown')" type="query"}%
Find all topics that have PNG attachments that have been added since 26th March 2007
%SEARCH{"attachments[name ~ '*.png' AND date >= d2n('2007-03-26')]"}%
Find all topics that have a field 'Threat' set to 'Amber' and 'cold virus' somewhere in the topic text.
%SEARCH{"Threat='Amber' AND text ~ '*cold virus*'"}%

Related Topics: IfStatements, SearchHelp, VarIF, VarGET, VarSET, VarSEARCH, FormattedSearch, TWiki:TWiki.QuerySearchPatternCookbook

Topic revision: r7 - 2011-04-04 - TWikiContributor
 
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