Class Schema
- java.lang.Object
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- org.apache.iceberg.Schema
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- 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
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Constructor Summary
Constructors Constructor 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)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description Accessor<StructLike>
accessorForField(int id)
Returns an accessor for retrieving the data fromStructLike
.java.lang.Integer
aliasToId(java.lang.String alias)
Returns the column id for the given column alias.Types.StructType
asStruct()
Returns the underlyingstruct type
for this schema.Types.NestedField
caseInsensitiveFindField(java.lang.String name)
Returns a sub-field by name as aTypes.NestedField
.Schema
caseInsensitiveSelect(java.lang.String... names)
Creates a projection schema for a subset of columns, selected by case insensitive namesSchema
caseInsensitiveSelect(java.util.Collection<java.lang.String> names)
Creates a projection schema for a subset of columns, selected by case insensitive namesjava.util.List<Types.NestedField>
columns()
Returns a List of thecolumns
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 aTypes.NestedField
.Types.NestedField
findField(java.lang.String name)
Returns a sub-field by name as aTypes.NestedField
.Type
findType(int id)
Returns theType
of a sub-field identified by the field id.Type
findType(java.lang.String name)
Returns theType
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.lang.String... names)
Creates a projection schema for a subset of columns, selected by name.Schema
select(java.util.Collection<java.lang.String> names)
Creates a projection schema for a subset of columns, selected by name.java.lang.String
toString()
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Constructor Detail
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Schema
public Schema(java.util.List<Types.NestedField> columns, java.util.Map<java.lang.String,java.lang.Integer> aliases)
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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)
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Schema
public Schema(java.util.List<Types.NestedField> columns)
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Schema
public Schema(java.util.List<Types.NestedField> columns, java.util.Set<java.lang.Integer> identifierFieldIds)
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Schema
public Schema(int schemaId, java.util.List<Types.NestedField> columns)
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Schema
public Schema(int schemaId, java.util.List<Types.NestedField> columns, java.util.Set<java.lang.Integer> identifierFieldIds)
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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)
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Schema
public Schema(Types.NestedField... columns)
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Schema
public Schema(int schemaId, Types.NestedField... columns)
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Method Detail
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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.
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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
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asStruct
public Types.StructType asStruct()
Returns the underlyingstruct type
for this schema.- Returns:
- the StructType version of this schema.
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columns
public java.util.List<Types.NestedField> columns()
Returns a List of thecolumns
in this Schema.
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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.
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identifierFieldNames
public java.util.Set<java.lang.String> identifierFieldNames()
Returns the set of identifier field names.
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findType
public Type findType(java.lang.String name)
Returns theType
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
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findType
public Type findType(int id)
Returns theType
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
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findField
public Types.NestedField findField(int id)
Returns the sub-field identified by the field id as aTypes.NestedField
.- Parameters:
id
- a field id- Returns:
- the sub-field or null if it is not found
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findField
public Types.NestedField findField(java.lang.String name)
Returns a sub-field by name as aTypes.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
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caseInsensitiveFindField
public Types.NestedField caseInsensitiveFindField(java.lang.String name)
Returns a sub-field by name as aTypes.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
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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
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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
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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
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accessorForField
public Accessor<StructLike> accessorForField(int id)
Returns an accessor for retrieving the data fromStructLike
.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 aStructLike
row
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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
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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
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caseInsensitiveSelect
public Schema caseInsensitiveSelect(java.lang.String... names)
Creates a projection schema for a subset of columns, selected by case insensitive namesNames 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
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caseInsensitiveSelect
public Schema caseInsensitiveSelect(java.util.Collection<java.lang.String> names)
Creates a projection schema for a subset of columns, selected by case insensitive namesNames 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
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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
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toString
public java.lang.String toString()
- Overrides:
toString
in classjava.lang.Object
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