io.r2dbc.spi

Interface ColumnMetadata

public interface ColumnMetadata

Represents the metadata for a column of the results returned from a query. The implementation of all methods except getName() is optional for drivers. Column metadata is optionally available as by-product of statement execution on a best-effort basis.

Method Summary

Modifier and Type	Method and Description
default Class<?>	getJavaType() Returns the primary Java type.
String	getName() Returns the name of the column.
default Object	getNativeTypeMetadata() Returns the native type descriptor that potentially exposes more metadata.
default Nullability	getNullability() Returns the nullability of column values.
default Integer	getPrecision() Returns the precision of the column.
default Integer	getScale() Returns the scale of the column.

Method Detail

getJavaType

@Nullable
default Class<?> getJavaType()

Returns the primary Java type. This type can be considered the native representation that is used to exchange values with the least loss in precision.

Implementation notes Drivers should implement this method. The method should return the actual type and refrain from returning Object.class. The default implementation returns null. Drivers may need to inspect the value and perform parts of decoding to determine the native Java type. This method should be expected to run in non-constant time.

Returns:

the primary Java type or null if the type is not available.

See Also:

Row.get(int)

getName

String getName()

Returns the name of the column.

The name does not necessarily reflect the column names how they are in the underlying tables but rather how columns are represented (e.g. aliased) in the result..

Returns:

the name of the column

getNativeTypeMetadata

@Nullable
default Object getNativeTypeMetadata()

Returns the native type descriptor that potentially exposes more metadata.

Implementation notes Drivers should implement this method if they can expose a driver-specific type metadata object exposing additional information. The default implementation returns null.

Returns:

the native type descriptor that potentially exposes more metadata or null if no native type descriptor is available.

getNullability

default Nullability getNullability()

Returns the nullability of column values.

Implementation notes Implementation of this method is optional. The default implementation returns Nullability.UNKNOWN.

Returns:

the nullability of column values.

See Also:

Nullability

getPrecision

@Nullable
default Integer getPrecision()

Returns the precision of the column.

For numeric data, this is the maximum precision. For character data, this is the length in characters. For datetime data types, this is the length in bytes required to represent the value (assuming the maximum allowed precision of the fractional seconds component). For binary data, this is the length in bytes. Returns null for data types where the column size is not applicable or if the precision cannot be provided.

Implementation notes Implementation of this method is optional. The default implementation returns null.

Returns:

the precision of the column or null if the precision is not available.

getScale

@Nullable
default Integer getScale()

Returns the scale of the column.

This is the number of digits to right of the decimal point. Returns null for data types where the scale is not applicable or if the precision cannot be provided.

Implementation notes Implementation of this method is optional. The default implementation returns null.

Returns:

the scale of the column or null if the scale is not available.