Class FileSchema

java.lang.Object

dev.hardwood.schema.FileSchema

public class FileSchema
extends Object

Root schema container representing the complete Parquet schema. Supports both flat schemas and nested structures (structs, lists).

See Also:

• File Format
• parquet.thrift

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static final class	FileSchema.Builder	Builder for constructing a FileSchema programmatically.
static final class	FileSchema.ElementBuilder	Declares the element of a LIST, or the value of a MAP: a primitive, a nested struct, a nested LIST, or a nested MAP.
static final class	FileSchema.StructBuilder	Declares the fields of a struct group.

Method Summary

Modifier and Type	Method	Description
static FileSchema.Builder	builder(String name)	Creates a builder for constructing a flat schema programmatically, for use with the writer.
static FileSchema	fromSchemaElements(List<SchemaElement> elements)	Reconstruct schema from Thrift SchemaElement list.
ColumnSchema	getColumn(int index)	Returns the column at the given zero-based index.
ColumnSchema	getColumn(FieldPath fieldPath)	Returns the column with the given field path.
ColumnSchema	getColumn(String name)	Returns the column with the given name or dot-separated path.
int	getColumnCount()	Returns the total number of leaf columns in this schema.
List<ColumnSchema>	getColumns()	Returns an unmodifiable list of all leaf columns in schema order.
SchemaNode	getField(String name)	Finds a top-level field by name in the schema tree.
String	getName()	Returns the schema name (typically "schema" or "message").
SchemaNode.GroupNode	getRootNode()	Returns the hierarchical schema tree representation.
boolean	isFlatSchema()	Returns true if this schema supports direct columnar access.
List<SchemaElement>	toSchemaElements()	Flattens this schema back into the depth-first SchemaElement list written to the file footer, the inverse of fromSchemaElements(List): the root element followed by each node in pre-order, groups carrying their child count.
String	toString()

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Method Details

getName

public String getName()

Returns the schema name (typically "schema" or "message").

getColumns

public List<ColumnSchema> getColumns()

Returns an unmodifiable list of all leaf columns in schema order.

getColumn

public ColumnSchema getColumn(int index)

Returns the column at the given zero-based index.

Parameters:

index - zero-based column index

getColumn

public ColumnSchema getColumn(String name)

Returns the column with the given name or dot-separated path.

For flat schemas, the name is the column name (e.g. "passenger_count"). For nested schemas, use the dot-separated field path (e.g. "address.zip") to avoid ambiguity when multiple nested columns share a leaf name.

Parameters:

name - column name or dot-separated field path

Throws:

IllegalArgumentException - if no column with the given name exists

getColumn

public ColumnSchema getColumn(FieldPath fieldPath)

Returns the column with the given field path.

Parameters:

fieldPath - path from schema root to leaf column

Throws:

IllegalArgumentException - if no column with the given path exists

getColumnCount

public int getColumnCount()

Returns the total number of leaf columns in this schema.

getRootNode

public SchemaNode.GroupNode getRootNode()

Returns the hierarchical schema tree representation.

getField

public SchemaNode getField(String name)

Finds a top-level field by name in the schema tree.

isFlatSchema

public boolean isFlatSchema()

Returns true if this schema supports direct columnar access. For such schemas, enabling direct columnar access without record assembly.

A schema supports columnar access if all top-level fields are primitives (no nested structs, lists, or maps) and no columns have repetition.

builder

public static FileSchema.Builder builder(String name)

Creates a builder for constructing a flat schema programmatically, for use with the writer.

Parameters:

name - the schema (message) name, conventionally "schema"

toSchemaElements

public List<SchemaElement> toSchemaElements()

Flattens this schema back into the depth-first SchemaElement list written to the file footer, the inverse of fromSchemaElements(List): the root element followed by each node in pre-order, groups carrying their child count.

fromSchemaElements

public static FileSchema fromSchemaElements(List<SchemaElement> elements)

Reconstruct schema from Thrift SchemaElement list.

toString

public String toString()

Overrides:

toString in class Object