Overview

A filter sets conditions for retrieving nodes and edges based on schemas and properties and is used within certain clause methods.

In UQL, filters are enclosed in curly braces {}. Filter expressions typically contain comparison operators such as =, >, <, and logical operators such as AND and OR. Each filter expression evaluates to a boolean (TRUE or FALSE) or null, validating nodes or edges only it returns TRUE.

General Filter

In this example, the filter {@user || @movie.rating > 3} specifies that the clause retrieves @user nodes or @movie nodes with a rating greater than 3:

find().nodes({@user || @movie.rating > 3}) as n
return n{*}

Simplified Filter

In this example, the filter {age} specifies that the clause retrieves nodes with an age property whose value, when subtracted by 30, is non-zero:

find().nodes({age - 30}) as n
return n{*}

The table below summarizes how different data types are evaluated as TRUE or FALSE in filters:

Inter-Step Filter

In a path template, you can use the system alias prev_n or prev_e to facilitate inter-step filtering.

This query finds 4-step outgoing transaction paths between @card nodes, ensuring that each transaction time is greater than the previous one:

n({@card}).re({@transfers}).n({@card})
  .re({@transfers.time > prev_e.time})[3]
  .n({@card}) as p
return p{*}

Any property called by prev_n or prev_e, such as the time property in the example, must be LTE-ed for acceleration.