I want to rename a Hive table if it exists, and not generate an error if it doesn't.
I need something like
ALTER TABLE IF EXISTS t1 RENAME TO t2;
but this doesn't run ("cannot recognize input near 'if' 'exists' 'rename' in alter table statement"), and neither do the variations that I've tried. This isn't covered in the docs (https://cwiki.apache.org/confluence/display/Hive/LanguageManual+DDL#LanguageManualDDL-RenameTable), maybe because it's not possible.
Does anyone know how to do this, or a workaround (e.g. try/catch, if it existed in Hive)?
I'm on Hive 1.2.
IF EXIST clause does not work in Hive CLI as of now. You can write program something like below for condition checking.
public class HiveAlterRenameTo {
private static String driverName = "org.apache.hadoop.hive.jdbc.HiveDriver";
public static void main(String[] args) throws SQLException {
// Register driver and create driver instance
Class.forName(driverName);
// get connection
Connection con = DriverManager.getConnection("jdbc:hive://localhost:10000/userdb", "", "");
// create statement
Statement stmt = con.createStatement();
// execute statement
Resultset res = stmt.executeQuery("SELECT count(*) FROM <Table_name> ;");
if (res > 0) {
// execute statement
stmt.executeQuery("ALTER TABLE employee RENAME TO emp;");
System.out.println("Table Renamed Successfully");
}
else {
System.out.println("Table Not exist");
}
con.close();
}
Related
This issue occurred in jdbc batch insert. I queried from an Oracle datasource, parsed the resultset and then inserted into another Oracle datasource. I have got the connect metadata and printed the current username along with url, both are invalid.
But when it went to batch update, I got the ora-00942 exception. I'm pretty sure all above works fine in database. Has anyone encountered this exception and can you give me some advice?
EDIT:
Ok, I got a table named photos for example in REMOTE_USER and I queried from it. It gave me a resultset, then I parse it after that INSERT it to LOCAL_USER.photos. I did query the LOCAL_USER.photos where I logon in from PL/SQL Developer. The interesting thing was I could do the select command but not the insert. Below is some part of code.
conn = datasource.getConnection(); // notice that it was target datasource
DatabaseMetaData connMetaData = conn.getMetaData();
String userName = connMetaData.getUserName();
resultSet = ds.getResultSet();
ResultSetMetaData metaData = resultSet.getMetaData();
int count = metaData.getColumnCount();
String insertSql = generateInsertSql(count, metaData, userName);
// this was generated through metaData , the output should be
// "insert into LOCAL_USER.photos(col1,col2) values(?,...)"
logger.error("insert clause is {}", insertSql);
ps = conn.prepareStatement(insertSql);
conn.setAutoCommit(false);
while (resultSet.next()) { // this was the original datasource
stageTotalNum++;
for (int i = 1; i <= count; i++) {
Object object = resultSet.getObject(i);
dealClobColumn(ps, i, object);
}
ps.addBatch();
if (stageTotalNum % 500L == 0L) {
ps.executeBatch(); // throws batchupdateexception.
ps.clearBatch();
conn.commit();
}
}
ps.executeBatch();
conn.commit();
It should be the blob type column which I didn't handle it the right way.
First I queried from original datasource then got the blob column of the resultset by
conn.getObject(index) . Next I insert the blob column into target datasource by conn.setObject. Of course that way wasn't working at all, so I changed to the following:
conn.setBlob(rs.getBlob(index)).
Although it worked fine in my own environemnt, but when the application ran in remote server, it kept annoying about the 'table or view does not exists'.The third version is:
conn.setBinaryStream(rs.getBlob(index).getBinaryStream());
Ok, this time it worked both my pc and remote server. Thanks to #codeLover's advice and link, it really hepled me and saved my time. Appreciated it!
I'm using MyBatis to create an Oracle table called User. If the table exists, it will just display the message Table User already exists and won't create it again. Currently I'm using this method.
public void createTable() {
try {
userMapper.createTable();
} catch (BadSqlGrammarException e) {
log.error("Table User already exists");
}
}
It kind of works by now. But I don't think this is a reliable way to do it, because there are multiple ways to trigger BadSqlGrammarException.
Apart from catching the exception, I also thought about checking if table exists or not first, but I cannot find a way to achieve it without calling a procedure.
Is there an elegant and correct way to check if table exists using Mybatis and Oracle?
I found a way to achieve this.
Add the following text to mybatis mapper file
<select id="checkTableExists" resultType="int">
<![CDATA[
SELECT COUNT(*) FROM user_tables WHERE table_name = 'CHECKSTATUS_LOG'
]]>
</select>
Declare it in the mapper class(along with createTable method, of course)
public interface CheckStatusLogMapper {
void createTable();
int checkTableExists();
}
Then you can use it like this
public void createTableIfNotExists) {
boolean b = checkTableExists();
if(!b) {
checkStatusLogMapper.createTable();
}
}
I am executing multiple queries concurrently and retrieving the results. But, the queries belong to multiple tables so, when resultset is retrieved, it is difficult to identify that a resultset belong to which table.
Can anyone help here as to how to identify the table names for each query resultset?
I tried below code but table name is blank!!!!
public static void getColumnNames(ResultSet rs) throws SQLException {
if (rs == null) {
return;
}
// get result set meta data
ResultSetMetaData rsMetaData = rs.getMetaData();
int numberOfColumns = rsMetaData.getColumnCount();
// get the column names; column indexes start from 1
for (int i = 1; i < numberOfColumns + 1; i++) {
String columnName = rsMetaData.getColumnName(i);
// Get the name of the column's table name
String tableName = rsMetaData.getTableName(i);
System.out.println("column name=" + columnName + " table=" + tableName + "");
}
}
I am calling this method like this:
jdbcTemplate.query(sql, new ResultSetExtractor<ResultSet>() {
#Override
public ResultSet extractData(ResultSet resultSet) throws SQLException,
DataAccessException {
getColumnNames(resultSet);
return resultSet;
}
});
Please advise, what is done wrong here? :(
You're not doing anything wrong here. The problem is caused by the method itself in connection with your DBMS or your JDBC driver, respectively.
See this doc please. 'table name or "" if not applicable' suggests that in your case the DBMS/driver does not provide the required information, causing the method to return an empty string.
I'm afraid, you'll have to find another way to detect which query the result originated from.
This query is returning the record with Min Create time Stamp for the Person Pers_ID when I run it in SQL Developer and the same query is not returning any value from Java JDBC connection.
Can you please help?
select PERS_ID,CODE,BEG_DTE
from PRD_HIST H
where PERS_ID='12345'
and CODE='ABC'
and CRTE_TSTP=(
select MIN(CRTE_TSTP)
from PRD_HIST S
where H.PERS_ID=S.PERS_ID
and PERS_ID='12345'
and EFCT_END_DTE is null
)
Java Code
public static List<String[]> getPersonwithMinCreateTSTP(final String PERS_ID,final String Category,final Connection connection){
final List<String[]> personRecords = new ArrayList<String[]>();
ResultSet resultSet = null;
Statement statement = null;
String PersID=null;
String ReportCode=null;
String effBegDate=null;
try{
statement = connection.createStatement();
final String query="select PERS_ID,CODE,EFCT_BEG_DTE from PRD_HIST H where PERS_ID='"+PERS_ID+"'and CODE='"+Category+"'and CRTE_TSTP=(select MIN(CRTE_TSTP) from PRD_HIST S where H.PERS_ID=S.PERS_ID and PERS_ID='"+PERS_ID+"' and EFCT_END_DTE is null)";
if (!statement.execute(query)) {
//print error
}
resultSet = statement.getResultSet();
while (resultSet.next()) {
PersID=resultSet.getString("PERS_ID");
ReportCode=resultSet.getString("CODE");
effBegDate=resultSet.getString("EFCT_BEG_DTE");
final String[] personDetails={PersID,ReportCode,effBegDate};
personRecords.add(personDetails);
}
} catch (SQLException sqle) {
CTLoggerUtil.logError(sqle.getMessage());
}finally{ // Finally is added to close the connection and resultset
try {
if (resultSet!=null) {
resultSet.close();
}if (statement!=null) {
statement.close();
}
} catch (SQLException e) {
//print error
}
}
return personRecords;
}
Print out your SQL SELECT statement from your java program and paste it into SQL*Plus and see what is happening. It's likely you're not getting your variables set to what you think you are. In fact, you're likely to see the error when you print out the SELECT statement without even running it - lower case values when upper is needed, etc.
If you still can't see it, post the actual query from your java code here.
I came here with similar problem - just thought I'd post my solution for others following - I hadn't run "COMMIT" after the inserts I'd made (via sqlplus) - doh!
The database table has records but the JDBC client can't retrieve the records.
Means the JDBC client doesn't have the select privileges. Please run the below query on command line:
grant all on emp to hr;
Is there any way I can get resultset object from one of jdbctemplate query methods?
I have a code like
List<ResultSet> rsList = template.query(finalQuery, new RowMapper<ResultSet>() {
public ResultSet mapRow(ResultSet rs, int rowNum) throws SQLException {
return rs;
}
}
);
I wanted to execute my sql statement stored in finalQuery String and get the resultset. The query is a complex join on 6 to 7 tables and I am select 4-5 columns from each table and wanted to get the metadata of those columns to transform data types and data to downstream systems.
If it is a simple query and I am fetching form only one table I can use RowMapper#mapRow and inside that maprow method i can call ResultsetExtractor.extractData to get list of results; but in this case I have complex joins in my query and I am trying to get resultset Object and from that resultset metadata...
The above code is not good because for each result it will return same resultset object and I dont want to store them in list ...
Once more thing is if maprow is called for each result from my query will JDBCTemplate close the rs and connection even though my list has reference to RS object?
Is there any simple method like jdbcTemplate.queryForResultSet(sql) ?
Now I have implemented my own ResultSet Extractor to process and insert data into downstream systems
sourceJdbcTemplate.query(finalQuery, new CustomResultSetProcessor(targetTable, targetJdbcTemplate));
This CustomResultSetProcessor implements ResultSetExtractor and in extractData method I am calling 3 different methods 1 is get ColumnTypes form rs.getMetaData() and second is getColumnTypes of target metadata by running
SELECT NAME, COLTYPE, TBNAME FROM SYSIBM.SYSCOLUMNS WHERE TBNAME ='TABLENAME' AND TABCREATOR='TABLE CREATOR'
and in 3rd method I am building the insert statement (prepared) form target columntypes and finally calling that using
new BatchPreparedStatementSetter()
{
#Override
public void setValues(PreparedStatement insertStmt, int i) throws SQLException{} }
Hope this helps to others...
Note that the whole point of Spring JDBC Template is that it automatically closes all resources, including ResultSet, after execution of callback method. Therefore it would be better to extract necessary data inside a callback method and allow Spring to close the ResultSet after it.
If result of data extraction is not a List, you can use ResultSetExtractor instead of RowMapper:
SomeComplexResult r = template.query(finalQuery,
new ResultSetExtractor<SomeComplexResult>() {
public SomeResult extractData(ResultSet) {
// do complex processing of ResultSet and return its result as SomeComplexResult
}
});
Something like this would also work:
Connection con = DataSourceUtils.getConnection(dataSource); // your datasource
Statement s = con.createStatement();
ResultSet rs = s.executeQuery(query); // your query
ResultSetMetaData rsmd = rs.getMetaData();
Although I agree with #axtavt that ResultSetExtractor is preferred in Spring environment, it does force you to execute the query.
The code below does not require you to do so, so that the client code is not required to provide the actual arguments for the query parameters:
public SomeResult getMetadata(String querySql) throws SQLException {
Assert.hasText(querySql);
DataSource ds = jdbcTemplate.getDataSource();
Connection con = null;
PreparedStatement ps = null;
try {
con = DataSourceUtils.getConnection(ds);
ps = con.prepareStatement(querySql);
ResultSetMetaData md = ps.getMetaData(); //<-- the query is compiled, but not executed
return processMetadata(md);
} finally {
JdbcUtils.closeStatement(ps);
DataSourceUtils.releaseConnection(con, ds);
}
}