org.apache.hadoop.hive.metastore.tools

Class SQLGenerator

java.lang.Object

org.apache.hadoop.hive.metastore.tools.SQLGenerator

public final class SQLGenerator
extends Object

Helper class that generates SQL queries with syntax specific to target DB todo: why throw MetaException?

Constructor Summary

Constructors

Constructor and Description
SQLGenerator(DatabaseProduct dbProduct, org.apache.hadoop.conf.Configuration conf)

Method Summary

Modifier and Type	Method and Description
String	addForUpdateClause(String selectStatement) Given a selectStatement, decorated it with FOR UPDATE or semantically equivalent construct.
String	addLimitClause(int numRows, String noSelectsqlQuery) Suppose you have a query "select a,b from T" and you want to limit the result set to the first 5 rows.
List<String>	createInsertValuesStmt(String tblColumns, List<String> rows) Genereates "Insert into T(a,b,c) values(1,2,'f'),(3,4,'c')" for appropriate DB
DatabaseProduct	getDbProduct()

Methods inherited from class java.lang.Object

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

Constructor Detail

SQLGenerator

public SQLGenerator(DatabaseProduct dbProduct,
                    org.apache.hadoop.conf.Configuration conf)

Method Detail

createInsertValuesStmt

public List<String> createInsertValuesStmt(String tblColumns,
                                           List<String> rows)

Genereates "Insert into T(a,b,c) values(1,2,'f'),(3,4,'c')" for appropriate DB

Parameters:

tblColumns - e.g. "T(a,b,c)"

rows - e.g. list of Strings like 3,4,'d'

Returns:

fully formed INSERT INTO ... statements

addForUpdateClause

public String addForUpdateClause(String selectStatement)
                          throws org.apache.hadoop.hive.metastore.api.MetaException

Given a selectStatement, decorated it with FOR UPDATE or semantically equivalent construct. If the DB doesn't support, return original select.

Throws:

org.apache.hadoop.hive.metastore.api.MetaException

addLimitClause

public String addLimitClause(int numRows,
                             String noSelectsqlQuery)
                      throws org.apache.hadoop.hive.metastore.api.MetaException

Suppose you have a query "select a,b from T" and you want to limit the result set to the first 5 rows. The mechanism to do that differs in different DBs. Make noSelectsqlQuery to be "a,b from T" and this method will return the appropriately modified row limiting query.

Note that if noSelectsqlQuery contains a join, you must make sure that all columns are unique for Oracle.

Throws:

org.apache.hadoop.hive.metastore.api.MetaException

getDbProduct

public DatabaseProduct getDbProduct()