Required. Controls over how job documents get ranked on top of
existing relevance score (determined by API algorithm). The
product of 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][goog
le.cloud.talent.v4beta1.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 < 100 characters in length.
Sample ranking expression (year + 25) * 0.25 - (freshness /
0.5)
