Evaluate expected result datatypes from json

exasol / virtual-schema-common-java

Common part of all Exasol Virtual Schema

MIT License

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Evaluate expected result datatypes from json #249

Closed ckunki closed 2 years ago

ckunki commented 2 years ago

Exasol version 8 and higher provide expected data types for result set as additional JSON content.

This enables JDBC-based virtual schema adapters to

avoid deriving the result data types from the values
save one query

The current ticket therefore requests to evaluate the additional elements from json and transfer them into internal Pojos.

ckunki commented 2 years ago

How should PushDownRequest inform about whether the json actually contained an entry "selectListDataTypes" or not?

return null or empty list?
return an optional or a list
have a separate method boolean hasSelectListDataTypes()

ckunki commented 2 years ago

Data type DECIMAL has two properties precisionand scale, reflected by method DataType.createDecimal(final int precision, final int scale). If these properties are missing in JSON to parse PushDownRequest from: should the parser provide default value(s)? E.g. call DataType.createDecimal(-1, -1)?