org.apache.druid.catalog.model.table

Interface TableFunction

All Known Implementing Classes:

BaseInputSourceDefn.AdHocTableFunction, BaseInputSourceDefn.PartialTableFunction, BaseTableFunction

public interface TableFunction

Representation of a SQL table function. The SQL module is not visible here. To avoid unnecessary dependencies, this class provides the information that Calcite needs, but without Calcite dependencies. Each function defines some number of arguments needed to create an external table. This same class can define a "from scratch" table, or to convert a partial table definition in the catalog into a full-defined external table.

The parameters tell Calcite the allowed parameters. Functions created from this class are most useful when used with named arguments:

 SELECT ... FROM TABLE(thisFn(foo -> "bar", answer -> 42))
 
 

 Calcite provides actual arguments as an array, with null values for arguments
 which the user did not provide. That form is not helpful for this use case.
 The caller converts those a map, with only the actual arguments set. The
 call also provides a row schema, obtained from the Calcite  EXTEND
 extension. The result is an ExternalTableSpec which the caller uses
 to create the Calcite form of an external table.

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	TableFunction.ParameterDefn
static class	TableFunction.ParameterType

Method Summary

Modifier and Type	Method and Description
ExternalTableSpec	apply(String fnName, Map<String,Object> args, List<ColumnSpec> columns, com.fasterxml.jackson.databind.ObjectMapper jsonMapper)
List<TableFunction.ParameterDefn>	parameters()

Method Detail

parameters

List<TableFunction.ParameterDefn> parameters()

apply

ExternalTableSpec apply(String fnName,
                        Map<String,Object> args,
                        List<ColumnSpec> columns,
                        com.fasterxml.jackson.databind.ObjectMapper jsonMapper)