@java.lang.Override
    public com.google.protobuf.ByteString getRankingExpressionBytes() {
      java.lang.Object ref = rankingExpression_;
      if (ref instanceof java.lang.String) {
        com.google.protobuf.ByteString b =
            com.google.protobuf.ByteString.copyFromUtf8((java.lang.String) ref);
        rankingExpression_ = b;
        return b;
      } else {
        return (com.google.protobuf.ByteString) ref;
      }
    }
<pre>
Required. Controls over how job documents get ranked on top of existing
relevance score (determined by API algorithm). A combination of the
ranking expression and relevance score is used to determine job's final
ranking position.

The syntax for this expression is a subset of Google SQL syntax.

Supported operators are: +, -, *, /, where the left and right side of
the operator is either a numeric
[Job.custom_attributes][google.cloud.talent.v4.Job.custom_attributes]
key, integer/double value or an expression that can be evaluated to a
number.

Parenthesis are supported to adjust calculation precedence. The
expression must be &lt; 200 characters in length.

The expression is considered invalid for a job if the expression
references custom attributes that are not populated on the job or if the
expression results in a divide by zero. If an expression is invalid for a
job, that job is demoted to the end of the results.

Sample ranking expression
(year + 25) * 0.25 - (freshness / 0.5)
</pre>

<code>string ranking_expression = 2 [(.google.api.field_behavior) = REQUIRED];</code>

@return The bytes for rankingExpression.
java-talent/proto-google-cloud-talent-v4/src/main/java/com/google/cloud/talent/v4/SearchJobsRequest.java