org.apache.drill.exec.record.metadata

Enum ColumnMetadata.StructureType

java.lang.Object

java.lang.Enum<ColumnMetadata.StructureType>

org.apache.drill.exec.record.metadata.ColumnMetadata.StructureType

All Implemented Interfaces:

Serializable, Comparable<ColumnMetadata.StructureType>

Enclosing interface:

ColumnMetadata

public static enum ColumnMetadata.StructureType
extends Enum<ColumnMetadata.StructureType>

Rough characterization of Drill types into metadata categories. Various aspects of Drill's type system are very, very messy. However, Drill is defined by its code, not some abstract design, so the metadata system here does the best job it can to simplify the messy type system while staying close to the underlying implementation.

Enum Constant Summary

Enum Constants

Enum Constant and Description
DICT Dict or repeated dict.
DYNAMIC Unknown, specified at runtime.
MULTI_ARRAY A repeated list.
PRIMITIVE Primitive column (all types except List, Map and Union.) Includes (one-dimensional) arrays of those types.
TUPLE Map or repeated map.
VARIANT Union or (non-repeated) list.

Method Summary

Modifier and Type	Method and Description
static ColumnMetadata.StructureType	valueOf(String name) Returns the enum constant of this type with the specified name.
static ColumnMetadata.StructureType[]	values() Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

PRIMITIVE

public static final ColumnMetadata.StructureType PRIMITIVE

Primitive column (all types except List, Map and Union.) Includes (one-dimensional) arrays of those types.

TUPLE

public static final ColumnMetadata.StructureType TUPLE

Map or repeated map. Also describes the row as a whole.

VARIANT

public static final ColumnMetadata.StructureType VARIANT

Union or (non-repeated) list. (A non-repeated list is, essentially, a repeated union.)

MULTI_ARRAY

public static final ColumnMetadata.StructureType MULTI_ARRAY

A repeated list. A repeated list is not simply the repeated form of a list, it is something else entirely. It acts as a dimensional wrapper around any other type (except list) and adds a non-nullable extra dimension. Hence, this type is for 2D+ arrays.

In theory, a 2D list of, say, INT would be an INT column, but repeated in to dimensions. Alas, that is not how it is. Also, if we have a separate category for 2D lists, we should have a separate category for 1D lists. But, again, that is not how the code has evolved.

DICT

public static final ColumnMetadata.StructureType DICT

Dict or repeated dict.

DYNAMIC

public static final ColumnMetadata.StructureType DYNAMIC

Unknown, specified at runtime. (Only for logical columns, not for physical columns.)

Method Detail

values

public static ColumnMetadata.StructureType[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (ColumnMetadata.StructureType c : ColumnMetadata.StructureType.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static ColumnMetadata.StructureType valueOf(String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

IllegalArgumentException - if this enum type has no constant with the specified name

NullPointerException - if the argument is null