– This document is a work in progress.
Overview
Templeton provides a REST-like web API for HCatalog and related Hadoop components. Developers can make HTTP requests to the Templeton web server to execute HCatalog DDL commands. With the REST APIs in place for HCatalog DDL commands, it is desirable to have a JAVA APIs in HCAT which can help end users to execute DDL commands without using CLI.
Design
New Classes
HCatClient
The HCatClient is an abstract class containing all the APIs permitted HCatalog DDL commands.
/**
* The abstract class HCatClient containing APIs for HCatalog DDL commands.
*/
public abstract class HCatClient {
/**
* Creates an instance of HCatClient.
*
* @param conf An instance of configuration.
* @return An instance of HCatClient.
*/
public HCatClient create(Configuration conf){
// Obtain details of implementation class and return an instance.
}
/**
* Gets the database like.
*
* @param regex The regular expression. Providing "*" would retrieve all the names
* of the databases.
* @return The list of all the database names.
* @throws HCatException
*/
public abstract List<String> getDatabaseLike(String regex) throws HCatException;
/**
* Gets the database.
*
* @param dbName The name of the database.
* @return An instance of HCatDatabaseInfo.
* @throws HCatException
*/
public abstract HCatDatabase getDatabase(String dbName) throws HCatException;
/**
* Creates the database.
*
* @param dbInfo An instance of HCatCreateDBDesc.
* @return true, if successful
* @throws HCatException
*/
public abstract boolean createDatabase(HCatCreateDBDesc dbInfo)
throws HCatException;
/**
* Deletes a database.
*
* @param dbName The name of the database to delete.
* @param ifExists Hive returns an error if the database specified does not exist,
* unless ifExists is set to true.
* @param mode This is set to either "restrict" or "cascade". Restrict will
* remove the schema if all the tables are empty. Cascade removes
* everything including data and definitions.
* @param userGroup The user group to use
* @param permissions The permissions string to use. The format is "rwxrw-r-x".
* @return true, if successful
* @throws HCatException
*/
public abstract boolean deleteDatabase(String dbName, boolean ifExists, String mode,
String userGroup, String permissions) throws HCatException;
/**
* Gets the tables like a pattern specified.
*
* @param dbName The name of the database.
* @param regex The regular expression. Providing "*" would retrieve all the names
* of the table.
* @return A list of all table names matching the specified pattern.
* @throws HCatException
*/
public abstract List<String> getTablesLike(String dbName, String regex)
throws HCatException;
/**
* Gets the table.
*
* @param dbName The name of the database.
* @param tableName The name of the table.
* @return An instance of HCatTableInfo.
* @throws HCatException
*/
public abstract HCatTable getTable(String dbName, String tableName)
throws HCatException;
/**
* Creates the table.
*
* @param createTableDesc An instance of HCatCreateTableDesc class.
* @return true, if successful.
* @throws HCatException the h cat exception
*/
public abstract boolean createTable(HCatCreateTableDesc createTableDesc)
throws HCatException;
/**
* Creates the table like an existing table.
*
* @param dbName The name of the database.
* @param existingTblName The name of the existing table.
* @param newTableName The name of the new table.
* @param ifExists the if exists
* @param isExternal Set to "true", if table has be created at a different
* location other than default.
* @param location The location for the table.
* @return true, if successful
* @throws HCatException
*/
public abstract boolean createTableLike(String dbName, String existingTblName,
String newTableName, boolean ifExists, boolean isExternal,
String location) throws HCatException;
/**
* Delete a table.
*
* @param dbName The name of the database.
* @param tableName The name of the table.
* @param ifExists Hive returns an error if the database specified does not exist,
* unless ifExists is set to true.
* @param userGroup The user group to use.
* @param permissions The permissions string to use. The format is "rwxrw-r-x".
* @return true, if successful
* @throws HCatException
*/
public abstract boolean deleteTable(String dbName, String tableName,
boolean ifExists, String userGroup, String permissions)
throws HCatException;
/**
* Renames a table.
*
* @param dbName The name of the database.
* @param oldName The name of the table to be renamed.
* @param newName The new name of the table.
* @param userGroup The user group to use.
* @param permissions The permissions string to use. The format is "rwxrw-r-x".
* @return true, if successful
* @throws HCatException
*/
public abstract boolean renameTable(String dbName, String oldName, String newName,
String userGroup, String permissions) throws HCatException;
/**
* Gets all the partitions.
*
* @param dbName The name of the database.
* @param tblName The name of the table.
* @return A list of partition names.
* @throws HCatException the h cat exception
*/
public abstract List<HCatPartition> getPartitions(String dbName, String tblName)
throws HCatException;
/**
* Gets the partition.
*
* @param dbName The database name.
* @param tableName The table name.
* @param partitionName The partition name, Comma separated list of col_name='value'.
* @return An instance of HCatPartitionInfo.
* @throws HCatException
*/
public abstract HCatPartition getPartition(String dbName, String tableName,
String partitionName) throws HCatException;
/**
* Adds the partition.
*
* @param partInfo An instance of HCatAddPartitionDesc.
* @return true, if successful
* @throws HCatException the h cat exception
*/
public abstract boolean addPartition(HCatAddPartitionDesc partInfo) throws HCatException;
/**
* Deletes partition.
*
* @param dbName The database name.
* @param tableName The table name.
* @param partitionName The partition name, Comma separated list of col_name='value'.
* @param ifExists Hive returns an error if the partition specified does not exist, unless ifExists is set to true.
* @param userGroup The user group to use.
* @param permissions The permissions string to use. The format is "rwxrw-r-x".
* @return true, if successful
* @throws HCatException
*/
public abstract boolean deletePartition(String dbName, String tableName,
String partitionName, boolean ifExists, String userGroup,
String permissions) throws HCatException;
/**
* List partitions by filter.
*
* @param dbName The database name.
* @param tblName The table name.
* @param filter The filter string,
* for example "part1 = \"p1_abc\" and part2 <= "\p2_test\"". Filtering can
* be done only on string partition keys.
* @return list of partitions
* @throws HCatException the h cat exception
*/
public abstract List<HCatPartition> listPartitionsByFilter(String dbName, String tblName,
String filter) throws HCatException;
/**
* Mark partition for event.
*
* @param dbName The database name.
* @param tblName The table name.
* @param partKVs the part k vs
* @param eventType the event type
* @throws HCatException the h cat exception
*/
public abstract void markPartitionForEvent(String dbName, String tblName,
Map<String, String> partKVs, PartitionEventType eventType)
throws HCatException;
/**
* Checks if is partition marked for event.
*
* @param dbName the db name
* @param tblName the tbl name
* @param partKVs the part k vs
* @param eventType the event type
* @return true, if is partition marked for event
* @throws HCatException the h cat exception
*/
public abstract boolean isPartitionMarkedForEvent(String dbName, String tblName,
Map<String, String> partKVs, PartitionEventType eventType)
throws HCatException;
/**
* Gets the delegation token.
*
* @param owner the owner
* @param renewerKerberosPrincipalName the renewer kerberos principal name
* @return the delegation token
* @throws HCatException the h cat exception
*/
public abstract String getDelegationToken(String owner, String renewerKerberosPrincipalName) throws
HCatException;
/**
* Renew delegation token.
*
* @param tokenStrForm the token str form
* @return the long
* @throws HCatException the h cat exception
*/
public abstract long renewDelegationToken(String tokenStrForm) throws HCatException;
/**
* Cancel delegation token.
*
* @param tokenStrForm the token str form
* @throws HCatException the h cat exception
*/
public abstract void cancelDelegationToken(String tokenStrForm) throws HCatException;
}
HCatCommandDesc
This is an abstract class that helps in validating user input, building valid command descriptors and queries.
/**
* The Class HCatCommandDesc contains methods which help in validating,
* building command descriptors and queries.
*/
public abstract class HCatCommandDesc{
public abstract void validateCommandDesc() throws HCatException;
abstract String buildQuery() throws HCatException;
abstract boolean isValidationComplete();
}
HCatCreateTableDesc
This class is a sub class of HCatCommandDesc and will be used by the users to create descriptor and validate it for the "create table" command.
HCatCreateDBDesc
This class is a sub class of HCatCommandDesc and will be used by the users to create descriptors and validate it for the "create database" command.
HCatAddPartitionDesc
This class is a sub class of HCatCommandDesc and will be used by the users to create descriptos and validate it for the "add partition" command.
HCatTable
This class encapsulates the table information returned the HCatClient implementation class and provides a uniform view to the user.
HCatDatabase
This class encapsulates the database information returned the HCatClient implementation class and provides a uniform view to the user.
HCatPartition
Usage
Configuration config = new Configuration();
config.add("hive-site.xml");
HCatClient client = HCatClient.create(config);
HCatCreateTableDesc desc = new HCatCreateTableDesc();
desc.setTableName("demo_table");
desc.setDatabaseName("db1");
desc.setFileFormat("rcfile");
ArrayList<HCatFieldSchema> cols = new ArrayList<HCatFieldSchema>();
cols.add(new HCatFieldSchema("col1", Type.INT, "comment1"));
cols.add(new HCatFieldSchema("col2", Type.STRING, "comment2"));
desc.setCols(cols);
//Validate
desc.validateCommandDesc();
boolean success = client.createTable(desc);