File Meta Data (Parquet Format)

코드 위치

• Line: 1106
• Link: struct FileMetaData

Structure §

/**
 * Description for file metadata
 */
struct FileMetaData {
	/** Version of this file **/
	1: required i32 version
 
	/** Parquet schema for this file.  This schema contains metadata for all the columns.
	* The schema is represented as a tree with a single root.  The nodes of the tree
	* are flattened to a list by doing a depth-first traversal.
	* The column metadata contains the path in the schema for that column which can be
	* used to map columns to nodes in the schema.
	* The first element is the root **/
	2: required list<SchemaElement> schema;
 
	/** Number of rows in this file **/
	3: required i64 num_rows
 
	/** Row groups in this file **/
	4: required list<RowGroup> row_groups
 
	/** Optional key/value metadata **/
	5: optional list<KeyValue> key_value_metadata
 
	/** String for application that wrote this file.  This should be in the format
	* <Application> version <App Version> (build <App Build Hash>).
	* e.g. impala version 1.0 (build 6cf94d29b2b7115df4de2c06e2ab4326d721eb55)
	**/
	6: optional string created_by
 
	/**
	* Sort order used for the min_value and max_value fields in the Statistics
	* objects and the min_values and max_values fields in the ColumnIndex
	* objects of each column in this file. Sort orders are listed in the order
	* matching the columns in the schema. The indexes are not necessary the same
	* though, because only leaf nodes of the schema are represented in the list
	* of sort orders.
	*
	* Without column_orders, the meaning of the min_value and max_value fields
	* in the Statistics object and the ColumnIndex object is undefined. To ensure
	* well-defined behaviour, if these fields are written to a Parquet file,
	* column_orders must be written as well.
	*
	* The obsolete min and max fields in the Statistics object are always sorted
	* by signed comparison regardless of column_orders.
	*/
	7: optional list<ColumnOrder> column_orders
 
	/** 
	* Encryption algorithm. This field is set only in encrypted files
	* with plaintext footer. Files with encrypted footer store algorithm id
	* in FileCryptoMetaData structure.
	*/
	8: optional EncryptionAlgorithm encryption_algorithm
 
	/** 
	* Retrieval metadata of key used for signing the footer. 
	* Used only in encrypted files with plaintext footer. 
	*/ 
	9: optional binary footer_signing_key_metadata
}

• version: File 의 버전
• schema
• row_groups
• key_value_metadata
• created_by
• column_orders
• encryption_algorithm
• footer_signing_key_metadata