As it does with other functions and operators, Teradata Database performs implicit conversion of types that are compatible with LOBs according to the rules of precedence. If you define a UDF that declares a LOB type parameter, you can call the UDF and pass a compatible argument.
IF the UDF declares this parameter type … | THEN you can call the UDF and pass this argument type … |
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CLOB |
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BLOB |
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In some cases, implicit conversions of types that are compatible with LOBs have performance consequences.
For example, suppose a UDF declares a BLOB parameter. If you call the UDF and pass in a VARBYTE column, Teradata Database converts the VARBYTE value into a temporary BLOB and passes it to the UDF. Because Teradata Database stores the temporary BLOB on disk, the performance cost of the conversion is significant.
A solution is to create an overloaded function that explicitly declares a VARBYTE argument.