public void setExpr(String expr) {
        this.expr = expr;
    }
<p>
Defines one or more numeric expressions that can be used to sort results or specify search or filter criteria.
You can also specify expressions as return fields.
</p>
<p>
You specify the expressions in JSON using the form <code>{"EXPRESSIONNAME":"EXPRESSION"}</code>. You can define
and use multiple expressions in a search request. For example:
</p>
<p>
<code> {"expression1":"_score*rating", "expression2":"(1/rank)*year"} </code>
</p>
<p>
For information about the variables, operators, and functions you can use in expressions, see <a href=
"http://docs.aws.amazon.com/cloudsearch/latest/developerguide/configuring-expressions.html#writing-expressions"
>Writing Expressions</a> in the <i>Amazon CloudSearch Developer Guide</i>.
</p>

@param expr
       Defines one or more numeric expressions that can be used to sort results or specify search or filter
       criteria. You can also specify expressions as return fields. </p>
       <p>
       You specify the expressions in JSON using the form <code>{"EXPRESSIONNAME":"EXPRESSION"}</code>. You can
       define and use multiple expressions in a search request. For example:
       </p>
       <p>
       <code> {"expression1":"_score*rating", "expression2":"(1/rank)*year"} </code>
       </p>
       <p>
       For information about the variables, operators, and functions you can use in expressions, see <a href=
       "http://docs.aws.amazon.com/cloudsearch/latest/developerguide/configuring-expressions.html#writing-expressions"
       >Writing Expressions</a> in the <i>Amazon CloudSearch Developer Guide</i>.
aws-java-sdk-cloudsearch/src/main/java/com/amazonaws/services/cloudsearchdomain/model/SearchRequest.java