xml 쿼리에서 CAST가 먹네요?

<query id="getMaxAndMinValueWithinExtraVars" action="select">
    <tables>
        <table name="documents" />
        <table name="document_extra_vars" alias="extra_vars" />
    </tables>
    <columns>
        <column name="MAX(CAST(extra_vars.value as signed))" alias="max" />
        <column name="MIN(CAST(extra_vars.value as signed))" alias="min" />
    </columns>
    <conditions>
        <condition operation="in" column="documents.module_srl" var="module_srl" filter="number" />
        <condition operation="in" column="documents.category_srl" var="category_srl" filter="number" pipe="and" />
        <condition operation="in" column="documents.member_srl" var="member_srl" filter="number" pipe="and" />
        <condition operation="in" column="documents.status" var="statusList" pipe="and" />
        <condition operation="equal" column="extra_vars.module_srl" default="documents.module_srl" pipe="and" />
        <condition operation="equal" column="extra_vars.document_srl" default="documents.document_srl" pipe="and" />
        <condition operation="equal" column="extra_vars.eid" var="var_eid" notnull="notnull" pipe="and" />
    </conditions>
</query>