Schema

java.lang.Object
- org.apache.iceberg.Schema

All Implemented Interfaces:

java.io.Serializable
```
public class Schema
extends java.lang.Object
implements java.io.Serializable
```
The schema of a data table.
Schema ID will only be populated when reading from/writing to table metadata, otherwise it will be default to 0.

See Also:

Serialized Form

Constructor Summary

Constructors
Constructor and Description
`Schema(int schemaId, java.util.List<Types.NestedField> columns)`
`Schema(int schemaId, java.util.List<Types.NestedField> columns, java.util.Map<java.lang.String,java.lang.Integer> aliases, java.util.Set<java.lang.Integer> identifierFieldIds)`
`Schema(int schemaId, java.util.List<Types.NestedField> columns, java.util.Set<java.lang.Integer> identifierFieldIds)`
`Schema(int schemaId, Types.NestedField... columns)`
`Schema(java.util.List<Types.NestedField> columns)`
`Schema(java.util.List<Types.NestedField> columns, java.util.Map<java.lang.String,java.lang.Integer> aliases)`
`Schema(java.util.List<Types.NestedField> columns, java.util.Map<java.lang.String,java.lang.Integer> aliases, java.util.Set<java.lang.Integer> identifierFieldIds)`
`Schema(java.util.List<Types.NestedField> columns, java.util.Set<java.lang.Integer> identifierFieldIds)`
`Schema(Types.NestedField... columns)`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`Accessor<StructLike>`	`accessorForField(int id)` Returns an accessor for retrieving the data from `StructLike`.
`java.lang.Integer`	`aliasToId(java.lang.String alias)` Returns the column id for the given column alias.
`Types.StructType`	`asStruct()` Returns the underlying `struct type` for this schema.
`Types.NestedField`	`caseInsensitiveFindField(java.lang.String name)` Returns a sub-field by name as a `Types.NestedField`.
`Schema`	`caseInsensitiveSelect(java.util.Collection<java.lang.String> names)` Creates a projection schema for a subset of columns, selected by case insensitive names
`Schema`	`caseInsensitiveSelect(java.lang.String... names)` Creates a projection schema for a subset of columns, selected by case insensitive names
`java.util.List<Types.NestedField>`	`columns()` Returns a List of the `columns` in this Schema.
`java.lang.String`	`findColumnName(int id)` Returns the full column name for the given id.
`Types.NestedField`	`findField(int id)` Returns the sub-field identified by the field id as a `Types.NestedField`.
`Types.NestedField`	`findField(java.lang.String name)` Returns a sub-field by name as a `Types.NestedField`.
`Type`	`findType(int id)` Returns the `Type` of a sub-field identified by the field id.
`Type`	`findType(java.lang.String name)` Returns the `Type` of a sub-field identified by the field name.
`java.util.Map<java.lang.String,java.lang.Integer>`	`getAliases()` Returns an alias map for this schema, if set.
`java.util.Set<java.lang.Integer>`	`identifierFieldIds()` The set of identifier field IDs.
`java.util.Set<java.lang.String>`	`identifierFieldNames()` Returns the set of identifier field names.
`java.lang.String`	`idToAlias(java.lang.Integer fieldId)` Returns the full column name in the unconverted data schema for the given column id.
`boolean`	`sameSchema(Schema anotherSchema)` Checks whether this schema is equivalent to another schema while ignoring the schema ID.
`int`	`schemaId()` Returns the schema ID for this schema.
`Schema`	`select(java.util.Collection<java.lang.String> names)` Creates a projection schema for a subset of columns, selected by name.
`Schema`	`select(java.lang.String... names)` Creates a projection schema for a subset of columns, selected by name.
`java.lang.String`	`toString()`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - Schema
```
public Schema(java.util.List<Types.NestedField> columns,
              java.util.Map<java.lang.String,java.lang.Integer> aliases)
```
  - Schema
```
public Schema(java.util.List<Types.NestedField> columns,
              java.util.Map<java.lang.String,java.lang.Integer> aliases,
              java.util.Set<java.lang.Integer> identifierFieldIds)
```
  - Schema
```
public Schema(java.util.List<Types.NestedField> columns)
```
  - Schema
```
public Schema(java.util.List<Types.NestedField> columns,
              java.util.Set<java.lang.Integer> identifierFieldIds)
```
  - Schema
```
public Schema(int schemaId,
              java.util.List<Types.NestedField> columns)
```
  - Schema
```
public Schema(int schemaId,
              java.util.List<Types.NestedField> columns,
              java.util.Set<java.lang.Integer> identifierFieldIds)
```
  - Schema
```
public Schema(int schemaId,
              java.util.List<Types.NestedField> columns,
              java.util.Map<java.lang.String,java.lang.Integer> aliases,
              java.util.Set<java.lang.Integer> identifierFieldIds)
```
  - Schema
```
public Schema(Types.NestedField... columns)
```
  - Schema
```
public Schema(int schemaId,
              Types.NestedField... columns)
```
- Method Detail
  - schemaId
```
public int schemaId()
```
    Returns the schema ID for this schema.
    Note that schema ID will only be populated when reading from/writing to table metadata, otherwise it will be default to 0.
  - getAliases
```
public java.util.Map<java.lang.String,java.lang.Integer> getAliases()
```
    Returns an alias map for this schema, if set.
    Alias maps are created when translating an external schema, like an Avro Schema, to this format. The original column names can be provided in a Map when constructing this Schema.
    
    Returns:
    
    a Map of column aliases to field ids
  - asStruct
```
public Types.StructType asStruct()
```
    Returns the underlying struct type for this schema.
    
    Returns:
    
    the StructType version of this schema.
  - columns
```
public java.util.List<Types.NestedField> columns()
```
    Returns a List of the columns in this Schema.
  - identifierFieldIds
```
public java.util.Set<java.lang.Integer> identifierFieldIds()
```
    The set of identifier field IDs.
    Identifier is a concept similar to primary key in a relational database system. It consists of a unique set of primitive fields in the schema. An identifier field must be at root, or nested in a chain of structs (no maps or lists). A row should be unique in a table based on the values of the identifier fields. Optional, float and double columns cannot be used as identifier fields. However, Iceberg identifier differs from primary key in the following ways:
    - Iceberg does not enforce the uniqueness of a row based on this identifier information. It is used for operations like upsert to define the default upsert key.
    - A nested field in a struct can be used as an identifier. For example, if there is a "last_name" field inside a "user" struct in a schema, field "user.last_name" can be set as a part of the identifier field.
    Returns:
    
    the set of identifier field IDs in this schema.
  - identifierFieldNames
```
public java.util.Set<java.lang.String> identifierFieldNames()
```
    Returns the set of identifier field names.
  - findType
```
public Type findType(java.lang.String name)
```
    Returns the Type of a sub-field identified by the field name.
    
    Parameters:
    
    name - a field name
    
    Returns:
    
    a Type for the sub-field or null if it is not found
  - findType
```
public Type findType(int id)
```
    Returns the Type of a sub-field identified by the field id.
    
    Parameters:
    
    id - a field id
    
    Returns:
    
    a Type for the sub-field or null if it is not found
  - findField
```
public Types.NestedField findField(int id)
```
    Returns the sub-field identified by the field id as a Types.NestedField.
    
    Parameters:
    
    id - a field id
    
    Returns:
    
    the sub-field or null if it is not found
  - findField
```
public Types.NestedField findField(java.lang.String name)
```
    Returns a sub-field by name as a Types.NestedField.
    The result may be a top-level or a nested field.
    
    Parameters:
    
    name - a String name
    
    Returns:
    
    a Type for the sub-field or null if it is not found
  - caseInsensitiveFindField
```
public Types.NestedField caseInsensitiveFindField(java.lang.String name)
```
    Returns a sub-field by name as a Types.NestedField.
    The result may be a top-level or a nested field.
    
    Parameters:
    
    name - a String name
    
    Returns:
    
    the sub-field or null if it is not found
  - findColumnName
```
public java.lang.String findColumnName(int id)
```
    Returns the full column name for the given id.
    
    Parameters:
    
    id - a field id
    
    Returns:
    
    the full column name in this schema that resolves to the id
  - aliasToId
```
public java.lang.Integer aliasToId(java.lang.String alias)
```
    Returns the column id for the given column alias. Column aliases are set by conversions from Parquet or Avro to this Schema type.
    
    Parameters:
    
    alias - a full column name in the unconverted data schema
    
    Returns:
    
    the column id in this schema, or null if the column wasn't found
  - idToAlias
```
public java.lang.String idToAlias(java.lang.Integer fieldId)
```
    Returns the full column name in the unconverted data schema for the given column id. Column aliases are set by conversions from Parquet or Avro to this Schema type.
    
    Parameters:
    
    fieldId - a column id in this schema
    
    Returns:
    
    the full column name in the unconverted data schema, or null if one wasn't found
  - accessorForField
```
public Accessor<StructLike> accessorForField(int id)
```
    Returns an accessor for retrieving the data from StructLike.
    Accessors do not retrieve data contained in lists or maps.
    
    Parameters:
    
    id - a column id in this schema
    
    Returns:
    
    an Accessor to retrieve values from a StructLike row
  - select
```
public Schema select(java.lang.String... names)
```
    Creates a projection schema for a subset of columns, selected by name.
    Names that identify nested fields will select part or all of the field's top-level column.
    
    Parameters:
    
    names - String names for selected columns
    
    Returns:
    
    a projection schema from this schema, by name
  - select
```
public Schema select(java.util.Collection<java.lang.String> names)
```
    Creates a projection schema for a subset of columns, selected by name.
    Names that identify nested fields will select part or all of the field's top-level column.
    
    Parameters:
    
    names - a List of String names for selected columns
    
    Returns:
    
    a projection schema from this schema, by name
  - caseInsensitiveSelect
```
public Schema caseInsensitiveSelect(java.lang.String... names)
```
    Creates a projection schema for a subset of columns, selected by case insensitive names
    Names that identify nested fields will select part or all of the field's top-level column.
    
    Parameters:
    
    names - a List of String names for selected columns
    
    Returns:
    
    a projection schema from this schema, by names
  - caseInsensitiveSelect
```
public Schema caseInsensitiveSelect(java.util.Collection<java.lang.String> names)
```
    Creates a projection schema for a subset of columns, selected by case insensitive names
    Names that identify nested fields will select part or all of the field's top-level column.
    
    Parameters:
    
    names - a List of String names for selected columns
    
    Returns:
    
    a projection schema from this schema, by names
  - sameSchema
```
public boolean sameSchema(Schema anotherSchema)
```
    Checks whether this schema is equivalent to another schema while ignoring the schema ID.
    
    Parameters:
    
    anotherSchema - another schema
    
    Returns:
    
    true if this schema is equivalent to the given schema
  - toString
```
public java.lang.String toString()
```
    Overrides:
    
    toString in class java.lang.Object

Class Schema

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

Schema

Schema

Schema

Schema

Schema

Schema

Schema

Schema

Schema

Method Detail

schemaId

getAliases

asStruct

columns

identifierFieldIds

identifierFieldNames

findType

findType

findField

findField

caseInsensitiveFindField

findColumnName

aliasToId

idToAlias

accessorForField

select

select

caseInsensitiveSelect

caseInsensitiveSelect

sameSchema

toString