org.apache.hadoop.hive.metastore.txn.jdbc.queries

Class GetOpenTxnTypeAndLockHandler

java.lang.Object

org.apache.hadoop.hive.metastore.txn.jdbc.queries.GetOpenTxnTypeAndLockHandler

All Implemented Interfaces:

ParameterizedQuery, QueryHandler<TxnType>, org.springframework.jdbc.core.ResultSetExtractor<TxnType>

public class GetOpenTxnTypeAndLockHandler
extends Object
implements QueryHandler<TxnType>

Constructor Summary

Constructors

Constructor and Description
GetOpenTxnTypeAndLockHandler(SQLGenerator sqlGenerator, long txnId)

Method Summary

Modifier and Type	Method and Description
TxnType	extractData(ResultSet rs)
String	getParameterizedQueryString(DatabaseProduct databaseProduct) Note that by definition select for update is divorced from update, i.e.
org.springframework.jdbc.core.namedparam.SqlParameterSource	getQueryParameters() An SqlParameterSource instance containing the required parameters for the query string.

Methods inherited from class java.lang.Object

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

Constructor Detail

GetOpenTxnTypeAndLockHandler

public GetOpenTxnTypeAndLockHandler(SQLGenerator sqlGenerator,
                                    long txnId)

Method Detail

getParameterizedQueryString

public String getParameterizedQueryString(DatabaseProduct databaseProduct)
                                   throws MetaException

Note that by definition select for update is divorced from update, i.e. you executeQuery() to read and then executeUpdate(). One other alternative would be to actually update the row in TXNS but to the same value as before thus forcing db to acquire write lock for duration of the transaction. SELECT ... FOR UPDATE locks the row until the transaction commits or rolls back. Second connection using `SELECT ... FOR UPDATE` will suspend until the lock is released.

Specified by:

getParameterizedQueryString in interface ParameterizedQuery

Parameters:

databaseProduct - A DatabaseProduct instance representing the type of the underlying HMS dabatabe.

Returns:

the txnType wrapped in an Optional

Throws:

MetaException - Thrown if the query string cannot be assembled.

getQueryParameters

public org.springframework.jdbc.core.namedparam.SqlParameterSource getQueryParameters()

Description copied from interface: ParameterizedQuery

An SqlParameterSource instance containing the required parameters for the query string. If the query is not parameterized, this method can either return null or an empty SqlParameterSource.

Specified by:

getQueryParameters in interface ParameterizedQuery

Returns:

Returns the SqlParameterSource containing the parameters for the query.

extractData

public TxnType extractData(ResultSet rs)
                    throws SQLException,
                           org.springframework.dao.DataAccessException

Specified by:

extractData in interface org.springframework.jdbc.core.ResultSetExtractor<TxnType>

Throws:

SQLException

org.springframework.dao.DataAccessException