Primary Key Lengths
Hi,
What is meant when someone says that your primary key length is too long??? This error I keep getting is really annoying me and I want to understand why it does this. Thanks everyone
Is this someone the database, one of your pals at the office, or your DBA?
If the someone is the database, what is the Oracle error number you see? Could it be ORA-01450? If the error message is ORA-01450, then you are trying to create a key with a length that is too long for the server software. I think the error message will tell you what the maximum key length is for your Oracle software version / operating system.
If it's one of your pals at the office, find some polite way to tell him to go suck an egg.
If it's your DBA, then listen to your DBA because DBAs know everything.
Similar Messages
-
Is there any restriction on the length of all Primary keys in a table
Hi all,
Is there any restriction on the length of all Primary keys in a data base table?
i have some 10 fields as primary key in a DB table and length exceeds 120 and getting a warning.
Please let me know will there be any problems in future with respect to the same?
With regards,
SumanthWell actually there are constraints like
Total of internal lengths of all primary key columns 1024 Bytes
Number of primary key columns per table 512
For other information about SAP database please refer to http://sapdb.org/sap_db_features.htm
Thanks & Regards,
Vivek Gaur
Alwayz in high spirits -
How to change (decrease) primary key column length?
Hi all,
I have plenty of data in the table and I need to decrease the primary key column from CHAR(17) to CHAR(13).
I try to use:
ALTER TABLE xx MODIFY (prmy_key (13));
but Oracle give:
ERROR at line 1:
ORA-01441: column to be modified must be empty to decrease column length
Can anyone give me advice on what is the best way to decrease column length? Thanks in advance for your help.To add to the above, I have done a simple test in the lines that I was suggesting the solution for this problem,
CREATE TABLE testA
(pk_col varchar2(20), jd date, constraint pk1 PRIMARY KEY(pk_col));
--Insert data into testA
create table testB as select * from testA;
TRUNCATE table testA;
ALTER TABLE testA modify(pk_col VARCHAR2(10));
INSERT INTO testA SELECT substr(pk_col, 1, 10), jd from testB;
DROP TABLE testB;
Select constraint_name, constraint_type, status from all_constraints
Where table_name = 'TESTA';
CONSTRAINT_NAME C STATUS
PK1 P ENABLEDAlter command is successful as the table is empty. TRUNCATE flushes the data and resets the high water mark keeping all the constraints. If we safely want to use the TRUNCATE as far as storage issues are concerned,
TRUNCATE table table_name reuse storage;
I think, this would accoplish what has been asked.
Let me know,
SriDHAR -
Deploying BMP Entity Bean with primary key calss
Hi,
I am using EJB 2.0 with and websphere studio 5.0 and database is sql server 2000.
My BMP Entity bean has a primary key class.From my client I am invoking the Entity Bean by calling it's findbyprimarykey method.
The home interface of my findbyprimarykey method returns a class of type Remote.But in the Entity Bean class,the return type is the primarykey class type.
My problem is invoking this findbyprimarykey from the client to get the remote interface so that the other business methods of the entity bean can be called.
The control goes into the ejbFindbyPrimaryKey but when it is returing from the Entity Bean class,it gives a remote exception (as the return type in Entity Bean class and Home interface are different for the findbyprimarykey method).
I think that somewhere in the deployment decriptor in my websphere,i have to specify the primarykey class type,which i am missing out and hence getting the error.
Please help me out with your advice and solution.
Thanks
Rahul PriyadarshiHi,
Sorry to disturb you again.
Even my code is also almost the same....i am pasting the code below...Please go through it and let me know if I have made any mistake..
EditVendorEntityBean.....(Bean Class)
package code.beans.EditVendor;
import code.beans.dataAccess.*;
import javax.ejb.CreateException;
import javax.ejb.RemoveException;
import javax.ejb.EntityBean;
import javax.ejb.EntityContext;
import javax.ejb.EJBException;
import javax.ejb.FinderException;
import javax.ejb.ObjectNotFoundException;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import java.sql.*;
import javax.sql.*;
import java.util.*;
* Bean implementation class for Enterprise Bean: EditVendorEntity
public class EditVendorEntityBean implements javax.ejb.EntityBean {
private static Hashtable dataSources = new Hashtable();
private String username;
private int Vendor_ID;
private int Category_Id;
private String Category_Name;
private String Vendor_Name;
private String Vendor_Address1;
private String Vendor_Address2;
private String Contact_Name;
private String Home_Phone;
private String Work_Phone;
private String email;
private String faxno;
private String userloginname;
private boolean dirtyFlag = false;
private EntityContext context;
private static final String DS_NAME = "jdbc/spiPOPS";
Connection con = null;
Statement stmt = null;
PreparedStatement st = null;
ResultSet res = null;
//***********************Business Methods*********************
// Begin of Busines Methods
public void setData (String[] catname, String vendorname,String vendadd1,String vendadd2,String vendcontact,String venoff,String venres,String mailid,String venfax) {
System.out.println("in setData where Vendor Id= "+ Vendor_ID);
boolean status=false;
boolean existing=false;
ArrayList cat=new ArrayList();
try
cat=getcategorylist(this.Vendor_ID);
catch(SQLException e)
System.out.println("Could not get category list");
System.out.println("Size of cat array -->" + cat.size() + " and string array size -->" + catname.length);
if(catname.length>0)
//Removing unwanted vendor categories for a particular vendor id
for(int i=0;i<cat.size();i++)
existing=false;
String tempdata=(String)cat.get(i);
for(int j=0;j<catname.length;j++)
if(tempdata.equals(catname[j]))
existing=true;
if(!existing)
try
delvencat(this.Vendor_ID,tempdata.trim());
catch(SQLException e)
System.out.println("Could not delete record in POPS_VENDOR_CATEGORY for -->" + tempdata);
//Adding new vendor categories for a particular vendor
try
for(int i=0;i<catname.length;i++)
status=false;
String strcat=catname;
status=checkcat(this.Vendor_ID,strcat.trim());
if(!status)
insertvencat(this.Vendor_ID,strcat.trim());
catch(SQLException e)
System.out.println("Could not insert or select from POPS_VENDOR_CATEGORY table");
this.Vendor_Name =vendorname;
this.Vendor_Address1 =vendadd1;
this.Vendor_Address2 =vendadd2;
this.Contact_Name =vendcontact;
this.Work_Phone =venoff;
this.Home_Phone =venres;
this.email =mailid;
this.faxno =venfax;
dirtyFlag = true;
System.out.println("Leaving set data method");
public Vector getData() {
Vector vctRec=new Vector();
ArrayList arrdatas = new ArrayList();
arrdatas.add(""+this.Vendor_ID);
arrdatas.add(this.Vendor_Name);
arrdatas.add(this.Vendor_Address1);
arrdatas.add(this.Vendor_Address2);
arrdatas.add(this.Contact_Name);
arrdatas.add(this.Work_Phone);
arrdatas.add(this.Home_Phone);
arrdatas.add(this.email);
arrdatas.add(this.faxno);
vctRec.addElement(arrdatas);
ArrayList cat=new ArrayList();
try
System.out.println("Calling getcategorylist from getdata with vendorid-->" + this.Vendor_ID);
cat = getcategorylist(this.Vendor_ID);
catch(SQLException e)
System.out.println("Could not get datas for category list");
vctRec.addElement(cat);
ArrayList allcats=new ArrayList();
try
allcats = getallcategorylist();
catch(SQLException e)
System.out.println("Could not get datas for category list");
vctRec.addElement(allcats);
dirtyFlag = false;
System.out.println("Before return statement in getdata with vector size -->" + vctRec.size());
return vctRec;
// End of Business Methods
//**************************Entity Bean Methods*******************************
* ejbActivate
public void ejbActivate() {
Vendor_ID = Integer.parseInt((String)context.getPrimaryKey());
System.out.println("Inside ejbActivate Vendor_ID-->"+ Vendor_ID);
* ejbLoad
public void ejbLoad() {
System.out.println("Inside ejbLoad ********" );
try {
loadRow();
}catch (Exception ex) {
System.out.println("Failed in loadRow()");
throw new EJBException("ejbLoad: " +
ex.getMessage());
* ejbPassivate
public void ejbPassivate() {
System.out.println("Inside ejbPassivate " );
Vendor_ID = 0;
* ejbRemove
public void ejbRemove() throws javax.ejb.RemoveException {
//Empty Method
* ejbStore
public void ejbStore() {
System.out.println("Inside ejbStore " );
try {
storeRow();
}catch (Exception ex) {
System.out.println("Exception thrown in storeRow" + ex.getMessage());
throw new EJBException("ejbLoad: " +
ex.getMessage());
* getEntityContext
public javax.ejb.EntityContext getEntityContext() {
return context;
* setEntityContext
public void setEntityContext(javax.ejb.EntityContext ctx) {
System.out.println("Inside setEntityContext " );
try{
con = getConnection(DS_NAME);
System.out.println("DB Connection Created!!");
catch(Exception e){
this.context = ctx;
* unsetEntityContext
public void unsetEntityContext() {
System.out.println("Inside unsetEntityContext " );
closeDbConnection(con, res, st);
this.context = null;
* ejbCreate
//code.beans.EditVendor.EditVendorEntityKey
public code.beans.EditVendor.EditVendorEntityKey ejbCreate(String vendorid)
throws javax.ejb.CreateException {
return new EditVendorEntityKey(vendorid);
//return null;
* ejbPostCreate
public void ejbPostCreate(String vendorid) throws javax.ejb.CreateException {
//Empty
* ejbFindByPrimaryKey
//code.beans.EditVendor.EditVendorEntityKey
public code.beans.EditVendor.EditVendorEntityKey ejbFindByPrimaryKey(
code.beans.EditVendor.EditVendorEntityKey primaryKey)
throws javax.ejb.FinderException {
try {
if(selectByPrimaryKey(Integer.parseInt(primaryKey.getVendorId()))) {
System.out.println("Leaving the findbyprimarykey method from the entity bean");
return primaryKey;
//return null;
}else {
throw new ObjectNotFoundException
("Row for id " + primaryKey + " not found.");
}catch (Exception ex) {
throw new EJBException("EXCEPTION IN ejbFindByPrimaryKey :- " + ex.getMessage());
/*********************** Database Utility Routines *************************/
private boolean selectByPrimaryKey(int priKey)
throws SQLException {
System.out.println("inside selectByPrimaryKey for primary key " + priKey);
String queryStr ="SELECT VENDOR_ID FROM POPS_VENDOR WHERE VENDOR_ID = " + priKey;
System.out.println("in selectByPrimaryKey where queryString is: "+ queryStr);
stmt = con.createStatement();
ResultSet result = stmt.executeQuery(queryStr);
if(!result.next()) {
stmt.close();
System.out.println("Did not find "+priKey);
return false;
else { //Found the primaryKey
Vendor_ID = result.getInt("VENDOR_ID");
stmt.close();
return true;
private void loadRow() throws SQLException {
System.out.println("inside loadRow ...");
stmt = con.createStatement();
String queryStr = "SELECT VENDOR_NAME,VENDOR_ADDRESS1,VENDOR_ADDRESS2,CONTACT_NAME,HOME_PHONE,WORK_PHONE,EMAIL_ID,FAX_NO " +
"FROM POPS_VENDOR WHERE VENDOR_ID=" + Vendor_ID;
System.out.println("Inside loadRow()***********"+queryStr);
ResultSet result = stmt.executeQuery(queryStr);
ArrayList catadatas=new ArrayList();
if(!result.next())
throw new SQLException("No record for primary key" + Vendor_ID);
this.Vendor_ID =Vendor_ID;
this.Vendor_Name =result.getString("VENDOR_NAME");
this.Vendor_Address1 =result.getString("VENDOR_ADDRESS1");
this.Vendor_Address2 =result.getString("VENDOR_ADDRESS2");
this.Contact_Name =result.getString("CONTACT_NAME");
this.Home_Phone =result.getString("HOME_PHONE");
this.Work_Phone =result.getString("WORK_PHONE");
this.email =result.getString("EMAIL_ID");
this.faxno =result.getString("FAX_NO");
System.out.println("Leaving loadrow method with loaded datas for vendor -->" + Vendor_ID);
stmt.close();
private ArrayList getcategorylist(int vendor) throws SQLException{
String queryStr ="SELECT DISTINCT(VENDOR_CAT) FROM POPS_VENDOR_CATEGORY WHERE VENDOR_ID=" + vendor;
System.out.println("Query for the cat list --> " + queryStr);
stmt = con.createStatement();
ResultSet result = stmt.executeQuery(queryStr);
ArrayList catdatas=new ArrayList();
try{
while(result.next())
catdatas.add(result.getString("VENDOR_CAT"));
catch (SQLException e){
stmt.close();
System.out.println("Could not retrieve datas for Category list");
stmt.close();
System.out.println("size off array for cat -->" + catdatas.size() + " and datas ->" + catdatas);
return catdatas;
private ArrayList getallcategorylist() throws SQLException{
//String queryStr ="SELECT DISTINCT(VENDOR_CAT) FROM POPS_VENDOR_CATEGORY";
StringBuffer strquery=new StringBuffer(20);
strquery.append("SELECT DISTINCT(CATEGORY_NAME) FROM POPS_CATEGORY");
stmt = con.createStatement();
//ResultSet result = stmt.executeQuery(queryStr);
ResultSet result = stmt.executeQuery(strquery.toString());
ArrayList catdatas=new ArrayList();
try{
while(result.next())
//catdatas.add(result.getString("VENDOR_CAT"));
catdatas.add(result.getString("CATEGORY_NAME"));
catch (SQLException e){
stmt.close();
System.out.println("Could not retrieve datas for All Category list");
stmt.close();
return catdatas;
private void delvencat(int vendor,String vencat) throws SQLException {
int update=-1;
stmt = con.createStatement();
String queryStr ="DELETE FROM POPS_VENDOR_CATEGORY WHERE VENDOR_ID = " + vendor + " AND VENDOR_CAT = '" + vencat.toUpperCase() + "'";
System.out.println("Delete query --> " + queryStr);
update= stmt.executeUpdate(queryStr);
if(update!=1)
System.out.println("Did not find data to delete");
stmt.close();
private void insertvencat(int vendor,String vencat) throws SQLException {
int update=-1;
String queryStr ="INSERT INTO POPS_VENDOR_CATEGORY(VENDOR_ID,VENDOR_CAT)" +
" VALUES(" + vendor +",'" + vencat + "')";
System.out.println("Insert query --> " + queryStr);
stmt = con.createStatement();
update=stmt.executeUpdate(queryStr);
if(update!=1)
System.out.println("Could not insert records in the database");
stmt.close();
private boolean checkcat(int vendor,String catven) throws SQLException {
boolean datastatus=false;
String queryStr ="SELECT VENDOR_ID FROM POPS_VENDOR_CATEGORY WHERE VENDOR_ID = " + vendor + " AND VENDOR_CAT = '" + catven.toUpperCase() + "'";
stmt = con.createStatement();
ResultSet result = stmt.executeQuery(queryStr);
datastatus=result.next();
stmt.close();
return datastatus;
private void storeRow() throws SQLException {
System.out.println("Inside ejb store");
if (!dirtyFlag) {
System.out.println("Skipping the UPDATE because object is not dirty");
return;
CallableStatement cs=null;
try{
cs = con.prepareCall("EXEC POPS_VENDOR_UPDATE " + this.Vendor_ID + ",'" + this.Vendor_Name + "','" + this.Vendor_Address1 + "','" + this.Vendor_Address2 + "','" + this.Contact_Name + "','" + this.Work_Phone + "','" + this.Home_Phone + "','" + this.email + "','" + this.faxno +"'");
System.out.println("\n\n SQL Statement : \n " + "EXEC POPS_VENDOR_UPDATE " + this.Vendor_ID + ",'" + this.Vendor_Name + "','" + this.Vendor_Address1 + "','" + this.Vendor_Address2 + "','" + this.Contact_Name + "','" + this.Work_Phone + "','" + this.Home_Phone + "','" + this.email + "','" + this.faxno +"'");
cs.executeUpdate();
catch (SQLException e){
cs.close();
System.out. println("\n\n Error in calling stored procedure POPS_INSERT_NEW_REQUEST \n\n"+ e.getMessage() + "\n\n");
cs.close();
dirtyFlag = false;
private Connection getConnection(String dbName) throws SQLException
String configuredDataSourceName = null;
if (dbName == null) {
System.out.println("Attemp to get connection failed. The requested database name is null");
DataSource dbSource = getDataSource(dbName);
return dbSource.getConnection();
private DataSource getDataSource(String dbName)
// looking from cache;
DataSource dbSource = (DataSource) dataSources.get(dbName);
if (dbSource == null) { //we need to find it from JNDI
try {
Context ic = new InitialContext();
dbSource = (DataSource) ic.lookup(dbName);
dataSources.put(dbName, dbSource);
}catch (NamingException e){
return dbSource;
* User calls this function to safely close an connection
* @param connt The connection a datasource
* @param rs The resulSet inside this connection
* @param statement The statement associate with this connection
private void closeDbConnection(Connection cont,ResultSet rs,Statement statement)
if (rs != null)
try {
rs.close();
} catch (SQLException ignored) {
ignored.printStackTrace();
if (statement != null)
try {
statement.close();
} catch (SQLException ignored) {
ignored.printStackTrace();
if (cont != null)
try {
cont.close();
} catch (SQLException ignored) {
ignored.printStackTrace();
} //closeDbConnection
EditVendorEntity (Remote Interface)
package code.beans.EditVendor;
import javax.ejb.EJBObject;
import java.rmi.RemoteException;
import java.util.*;
* Remote interface for Enterprise Bean: EditVendorEntity
public interface EditVendorEntity extends javax.ejb.EJBObject {
public void setData (String[] catname, String vendorname,String vendadd1,String vendadd2,String vendcontact,String venoff,String venres,String mailid,String venfax)
throws RemoteException;
public Vector getData() throws RemoteException;
EditVendorEntityHome (Home Interface)
package code.beans.EditVendor;
import java.rmi.RemoteException;
import javax.ejb.CreateException;
import javax.ejb.FinderException;
import javax.ejb.DuplicateKeyException;
import javax.ejb.EJBHome;
import java.util.*;
* Home interface for Enterprise Bean: EditVendorEntity
public interface EditVendorEntityHome extends javax.ejb.EJBHome {
* Creates an instance from a key for Entity Bean: EditVendorEntity
public code.beans.EditVendor.EditVendorEntity create(String vendorid)
throws javax.ejb.CreateException, java.rmi.RemoteException;
* Finds an instance using a key for Entity Bean: EditVendorEntity
public code.beans.EditVendor.EditVendorEntity findByPrimaryKey(
code.beans.EditVendor.EditVendorEntityKey Vendor_ID)
throws javax.ejb.FinderException, java.rmi.RemoteException;
EditVendorEntityKey (Primary Key Class)
package code.beans.EditVendor;
* Key class for Entity Bean: EditVendorEntity
public class EditVendorEntityKey implements java.io.Serializable {
static final long serialVersionUID = 3206093459760846163L;
public String primkey;
* Creates an empty key for Entity Bean: EditVendorEntity
public EditVendorEntityKey() { }
public EditVendorEntityKey(String primarykey) {
this.primkey=primarykey;
public String getVendorId() {
return primkey;
* Returns true if both keys are equal.
public boolean equals(java.lang.Object otherKey) {
if (otherKey instanceof code.beans.EditVendor.EditVendorEntityKey) {
code.beans.EditVendor.EditVendorEntityKey o =
(code.beans.EditVendor.EditVendorEntityKey) otherKey;
return (primkey.equals(otherKey));
return false;
* Returns the hash code for the key.
public int hashCode() {
return (primkey.hashCode());
Please go through and give me your comments and solution...
Thanks in advance
Rahul -
Problem with a primary key when creating a new record in Forms
My table has a field - MDD_KEY - that is a primary key. It is updated from a sequence with a before-insert database trigger. I know this works properly as the primary key was accurately populated when I inserted 1433 records.
In Forms 6, I have a form based on that table. I have set the mdd_key as a hidden field because I assume it will be entered by the before-insert trigger. However, when I enter data into the table, and then try to save it, I get a FRM-40202: Field must be entered. - followed by - FRM-40222: Disabled item MDD_KEY failed validation.
If I set DATA Required to no, when I try to save I get an FRM-40600: Record has already been inserted - but no such record exists in the database. I know this record is unique and does NOT exist because I deliberately made it up.
In the property palatte, the attributes of the field are:
DATA Data Type Number
Required Yes
DATABASE Database Item Yes
Primary Key Yes
Query Only No
Query Allowed Yes
Query Length 0
Insert Allowed Yes
Update Allowed Yes
Update Only if Null No
Lock Record No
I assume that my problem is that with a new record, the form wants to see the MDD_KEY populated before it saves - but that isn't going to happen until the before insert trigger fires in the database. I assume I have to populate that field within forms, but how do I do that without messing up the database trigger/sequence? I will have to load more data directly into the database - so I need the database trigger in place.
I have not used primary keys before so I am more than a little bit confused about how and when it should be populated when a new record is created in Forms.
Any help would be appreciated as I cannot enter new data into my form (works well with existing data).
Thanks
Glennhi
if u have any problem using seq then try that statemetn ur block level in ur form
PRE-INSERT trigger
select nvl(max(nvl(srno,0)),0)+1 into :srno from tablename;
Rizwan -
Hi,
I got these question in interview Plz answer them
1. Maximum number of primary keys u can use for a table?
2. Maximum number of indexes u can create?
3. Maximum number of secondary indexes?
4. Maximum number fields in a table?
5. Maximum length of primary key field?
Plz answer these questions
regards,
kumar>>1. Maximum number of primary keys u can use for a table?
16
>>2. Maximum number of indexes u can create?
>>3. Maximum number of secondary indexes?
Only 16 Primary Index and n number of secondary indexes.
>>4. Maximum number fields in a table?
249
>>5. Maximum length of primary key field?
255
Cheers,
Hakim
Mark all useful answers..Close the thread once your question has been answered. -
How to get primary keys in some order with joins?
Hi, I build BBS using BDB as backend database, forum database, topic database and post database share one environment. This BBS web application is multi-thread program. If user selects one forum, its topics will be listed in order of last reply time;selecting one topic, posts are listed in order of reply time as well.
struct forum {
UInt16 forumID;
string forumName;
string _lastPoster; // who is the last one replied in this forum
struct topic {
UInt32 topicID;
UInt16 forumID; // topic comes from this forum
string title; // topic title
UInt64 dateOfLastReply; // when last reply to this topic happen
struct post {
UInt64 postID;
UInt32 topicID; // post comes from this topic
string title; // post title as of topic
UInt64 dateOfPost; // when this post is created
I create one primary database and two secondary databases for topic, primary key is topicID, secondary key are forumID and dateOfLastReply respectively, and I want to show 1st 25 topics in latest reply time order on the 1st browser page, 2nd 25 topics on the 2nd browser page, and etc.
if using SQL, it will be: SELECT topicID FROM topic WHERE forumID=xx ORDER BY dateOfLastReply DESC
From performance perspective, I want get all topics id of one same forum, and need them come in reply time order, then retrieve topic one by one based on returned topicID, how can I do this? guess I have to use joins.
Plus, do you have any suggestion about retrieval performance given the fact that topics retrieval will happen each time browser want to request the next page, that is, 2nd 25 topics of this forum?
Is DB_DBT_MULTIPLE helpful to me?
thanks.
Edited by: tiplip on 2011-1-22 上午5:43
Edited by: tiplip on 2011-1-22 下午5:52
Edited by: tiplip on 2011-1-23 下午7:42Hi tiplip,
Bellow I will describe how you can support "SELECT * FROM table WHERE X = key ORDER BY Y" queries using Berkeley DB, which, as you suspected, should be done by using a composite index.
First of all, think of Berkeley DB as the storage engine underneath an RDBMS. In fact, Berkeley DB was the first "generic data storage library" implemented underneath MySQL. As such, Berkeley DB has API calls and access methods that can support any RDBMS query. However, since BDB is just a storage engine, your application has to provide the code that accesses the data store with an appropriate sequence of steps that will implement the behavior that you want.
If you have two indices in SQL, each on a single column (call them X and Y), and you do:
SELECT * FROM table WHERE X = key ORDER BY Y;then there are three plausible query plans:
(1) scan the whole table, ignore both indices, filter by X = key then sort by Y;
(2) use the index on Y to scan all rows in the required order, filter by X = key;
(3) use the index on X, find the matching rows, then sort by Y.
There are cases where (1) would be fastest, because it has all of the columns from one scan (the other query plans will do random lookups on the primary for each row). This assumes that the data can fit into memory and the sort is fast.
Query plan (2) will be fastest if the selectivity is moderate to high, looking up rows in the main table is fast, and sorting the rows is very slow for some reason (e.g., some complex collation).
Query plan (3) will be fastest if the selectivity is small (only a small percentage of the rows in the table matches). This should be the best case for us, making it the best choice in a Berkeley DB key/value application.
The optimal plan would result from having a composite index on (X, Y), which can return just the desired rows in the desired order. Of course, it does cost additional time and space to maintain that index. But note that you could have this index instead of a simple index on X: it can be used in any query the simple index could be used in.
Records in Berkeley DB are (key, value) pairs. Berkeley DB supports only a few logical operations on records. They are:
* Insert a record in a table.
* Delete a record from a table.
* Find a record in a table by looking up its key.
* Update a record that has already been found.
Notice that Berkeley DB never operates on the value part of a record. Values are simply payload, to be stored with keys and reliably delivered back to the application on demand. Both keys and values can be arbitrary byte strings, either fixed-length or variable-length.
So, in case of a "SELECT * FROM X WHERE id=Y ORDER BY Z" query, our suggestion, from Berkeley DB's point of view, would be for you to use a composite index (as it would be in SQL), where a string created as X_Y should do the trick, as explained in the following scenario.
Primary:
X Y
1 10 abc
2 10 aab
3 20 bbc
4 10 bba
5 20 bac
6 30 cbaSecondary:
10_aab 2
10_abc 1
10_bba 4
20_bac 5
20_bbc 3
30_cba 6If the query looks like this:
'SELECT * FROM primarydb WHERE X = 10 ORDER by Y'the application can run a cursor on the secondary and begin the loop with the DB_SET_RANGE flag on 10. When iterating with DB_NEXT, this will return:
2 10 aab
1 10 abc
4 10 bbcThe application must check for the end of the range inside the loop, in this case it should stop when it hits 20_bac.
As in SQL, retrieving by a secondary key is remarkably similar to retrieving by a primary key and the Berkeley DB call will look similar to its primary equivalent.
tiplip wrote:
Plus, do you have any suggestion about retrieval performance given the fact that topics retrieval will happen each time browser want to request the next page, that is, 2nd 25 topics of this forum?As you are concerned about the performance, I think this would be the fastest solution. Of course, you can tune the performance at a later time, after you have the functionality in place. What I think you should do first is to increase the cache size and test with a bigger database page size, and maybe to configure the transactional subsystem (in case you use one).
If you are not very familiar with how to implement the above in BDB, please read the Guide to Oracle Berkeley DB for SQL Developers, available at: http://www.oracle.com/technetwork/articles/seltzer-berkeleydb-sql-086752.html
You will also need to be familiar with the following documentation:
Related documentation pages:
Secondary indexes - http://download.oracle.com/docs/cd/E17076_01/html/programmer_reference/am_second.html
Cursor operations - http://download.oracle.com/docs/cd/E17076_01/html/programmer_reference/am_cursor.html#am_curget
DBcursor->get() - http://download.oracle.com/docs/cd/E17076_01/html/api_reference/C/dbcget.html
DB_SET_RANGE - http://download.oracle.com/docs/cd/E17076_01/html/api_reference/C/dbcget.html#dbcget_DB_SET_RANGE
If my answer helps you with your question, please go ahead and rate it as Helpful or Correct, and the forum thread as answered. For each unrelated question, please create a new forum thread.
Good luck with building your forum application,
Bogdan Coman
PS: If you are a BDB licensed customer, you can also use My Oracle Support (https://support.oracle.com) to visit the KM note 1210173.1, that discusses the same topic. -
Primary key in master detail form
i have a situation where i need to access the value of primary key (primary key is hidden) in a master-detail form.
i need to access the primary key in the javascript onClick event of the button. i'm using the following code in the ...before displaying the form event :-
htp.p('<script language="JavaScript1.3">
<!--
function getField(form,fieldName)
var objName = "";
var tmp = "";
var dAction = "";
var sel_idx = 0;
var cnt = 0;
var instance = 0;
var slicedName;
var fillData = new Array();
for (var i = 0; i < form.length; i++)
slicedName = form.elements.name.split(".");
tmp = slicedName[2];
instance = parseInt(slicedName[3],10);
if (!tmp)
continue;
objName = tmp;
if (objName == fieldName)
return form.elements[i].value;
//-->
</script>');
and then i'm calling this javascript in onClick event of the button as follows :
var_get_val = getField(this.FORM,'PROD_ID');
this script works for a form with single block but, does not work with the master detail form.
what is wrong here ... ??
any ideas or suggestions ...??
thanx a lot.
nullThank you, Denes,
but isn_t there a simplier way to use a third column ?
I will keep your idea in mind and try out as soon as possible.
With kind regards,
Hergen. -
Transporting table entry with primary key 120 char
Hi all,
I have 2 separate questions which I feel are closely related.
In the url:
http://help.sap.com/saphelp_nw04/helpdata/en/cf/21eb6e446011d189700000e8322d00/content.htm
It says:....
<i>If the key length is greater than 120, there are restrictions when transporting table entries. The key can only be specified up to a maximum of 120 places in a transport. If the key is larger than 120, table entries must be transported generically.</i>
<b>How do I transport the table entries "generically" for such a table?</b>
To further illustrate my actual problem:
My problem in the real world lies with the MIMETYPES table, maintained in trx SMW0.
I select the mime types row by row and do a <u>Table Entry > Transport Entries,</u> but get an error that says
<i>"Key entry for table MIMETYPES may only be generic"</i>.
As a result it fails to attach to my transport.
(Note: the primary key of MIMETYPES is 128 chars long)
The Diagnosis long text says "<i>The key is longer than allowed by the Change and Transport System (120 characters</i>)."
The Procedure says:
<i>1. Make sure that you only specify the character fields before the
first non-character key field. You must enter the key with a generic
ending. Enter the generic symbol directly after the specified part
of the key.
2. You must enter the generic symbol at the latest in the 120th
character of the key. </i>
<b>What is this generic symbol that i need to insert at the 120th position??</b>
Message was edited by:
Kevin Wong
Message was edited by:
Kevin Wong
Message was edited by:
Kevin WongThanks Nick!
So the mysterious "generic character" is actually the asterisk (*). It works.
Strange tho as the error long text says to insert the "generic character" at the 120th character position of the key, but I found that altho I can save it, the transport still fails with the same error.
I tried placing the * right after the key value e.g.
KEY123*
and it worked.
Thanks again! -
Could someone please help as I haven't been able to find the answer from the TopLink doc?
In the TopLink's implementation of JDO Spec, what are the allowed the primary key types for a Persistence class?
I appreciate your information.
HaiweiDoug, thanks very much for your response.
My immediate problem is this:
I am getting an exception (see below) while trying to use Byte[] as the primary key type in my testing. I wonder whether TopLink supports Byte[] primary key type.
I use TopLinks' getObjectById method.
A more general question, does TopLink support other data types for primary key (java.util.Date, java.sql.Date, java.sql.Time, java.sql.Timestamp, java.util.GregorianCalendar, etc.)? Your response seems to say Yes. Could you please confirm?
Here is the exception. The input Byte[] has value 25, with length of 1.
[4/19/04 12:26:26:126 EDT] 78c09b9c SystemOut O ServerSession(2046122932)--Exception [TOPLINK-3001] (OracleAS TopLink - 10g (9.0.4) (Build 031126)): oracle.toplink.exceptions.ConversionException
Exception Description: The object [[Ljava.lang.Byte;@4ffd9b9f], of class [class [Ljava.lang.Byte;], could not be converted to [class [B].Local Exception Stack:
Exception [TOPLINK-3001] (OracleAS TopLink - 10g (9.0.4) (Build 031126)): oracle.toplink.exceptions.ConversionException
Exception Description: The object [[Ljava.lang.Byte;@4ffd9b9f], of class [class [Ljava.lang.Byte;], could not be converted to [class [B].
at oracle.toplink.exceptions.ConversionException.couldNotBeConverted(ConversionException.java:35)
at oracle.toplink.internal.helper.ConversionManager.convertObjectToByteArray(ConversionManager.java:278)
at oracle.toplink.internal.helper.ConversionManager.convertObject(ConversionManager.java:129)
at oracle.toplink.internal.databaseaccess.DatabasePlatform.convertObject(DatabasePlatform.java:556)
at oracle.toplink.internal.databaseaccess.DatabasePlatform.convertToDatabaseType(DatabasePlatform.java:581)
at oracle.toplink.internal.databaseaccess.DatabasePlatform.appendParameter(DatabasePlatform.java:182)
at oracle.toplink.internal.databaseaccess.DatabaseCall.appendParameter(DatabaseCall.java:110)
at oracle.toplink.queryframework.SQLCall.translate(SQLCall.java:343)
at oracle.toplink.internal.queryframework.CallQueryMechanism.executeCall(CallQueryMechanism.java:129)
at oracle.toplink.internal.queryframework.CallQueryMechanism.executeCall(CallQueryMechanism.java:111)
at oracle.toplink.internal.queryframework.CallQueryMechanism.selectOneRow(CallQueryMechanism.java:584)
at oracle.toplink.internal.queryframework.ExpressionQueryMechanism.selectOneRowFromTable(ExpressionQueryMechanism.java:792)
at oracle.toplink.internal.queryframework.ExpressionQueryMechanism.selectOneRow(ExpressionQueryMechanism.java:763)
at oracle.toplink.queryframework.ReadObjectQuery.execute(ReadObjectQuery.java:340)
at oracle.toplink.queryframework.DatabaseQuery.execute(DatabaseQuery.java:498)
at oracle.toplink.queryframework.ReadQuery.execute(ReadQuery.java:111)
at oracle.toplink.publicinterface.Session.internalExecuteQuery(Session.java:1968)
at oracle.toplink.threetier.ServerSession.internalExecuteQuery(ServerSession.java:629)
at oracle.toplink.publicinterface.Session.executeQuery(Session.java:1096)
at oracle.toplink.publicinterface.Session.executeQuery(Session.java:1048)
at com.ford.it.persistence.jdo.toplink.PersistenceManagerWrapper.getObjectById(PersistenceManagerWrapper.java:130)
at com.ford.it.persistence.jdo.toplink.unittest.PersistenceManagerWrapperTest.testGetObjectById13(PersistenceManagerWrapperTest.java:423)
at java.lang.reflect.Method.invoke(Native Method)
at junit.framework.TestCase.runTest(TestCase.java:154)
at junit.framework.TestCase.runBare(TestCase.java:127)
at org.apache.cactus.ServletTestCase.runCactusTest(ServletTestCase.java:291)
at org.apache.cactus.ServletTestCase.runBare(ServletTestCase.java:263)
at org.apache.cactus.server.AbstractWebTestCaller.doTest(AbstractWebTestCaller.java:156)
at org.apache.cactus.server.AbstractWebTestController.handleRequest_aroundBody0(AbstractWebTestController.java:130)
at org.apache.cactus.server.AbstractWebTestController.handleRequest_aroundBody1$advice(AbstractWebTestController.java:158)
at org.apache.cactus.server.AbstractWebTestController.handleRequest(AbstractWebTestController.java)
at org.apache.cactus.server.ServletTestRedirector.doPost_aroundBody2(ServletTestRedirector.java:138)
at org.apache.cactus.server.ServletTestRedirector.doPost_aroundBody3$advice(ServletTestRedirector.java:158)
at org.apache.cactus.server.ServletTestRedirector.doPost(ServletTestRedirector.java)
at org.apache.cactus.server.ServletTestRedirector.doGet_aroundBody0(ServletTestRedirector.java:109)
at org.apache.cactus.server.ServletTestRedirector.doGet_aroundBody1$advice(ServletTestRedirector.java:158)
at org.apache.cactus.server.ServletTestRedirector.doGet(ServletTestRedirector.java)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:740)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at com.ibm.ws.webcontainer.servlet.StrictServletInstance.doService(StrictServletInstance.java:110)
at com.ibm.ws.webcontainer.servlet.StrictLifecycleServlet._service(StrictLifecycleServlet.java:174)
at com.ibm.ws.webcontainer.servlet.IdleServletState.service(StrictLifecycleServlet.java:313)
at com.ibm.ws.webcontainer.servlet.StrictLifecycleServlet.service(StrictLifecycleServlet.java:116)
at com.ibm.ws.webcontainer.servlet.ServletInstance.service(ServletInstance.java:283)
at com.ibm.ws.webcontainer.servlet.ValidServletReferenceState.dispatch(ValidServletReferenceState.java:42)
at com.ibm.ws.webcontainer.servlet.ServletInstanceReference.dispatch(ServletInstanceReference.java:40)
at com.ibm.ws.webcontainer.webapp.WebAppRequestDispatcher.handleWebAppDispatch(WebAppRequestDispatcher.java:948)
at com.ibm.ws.webcontainer.webapp.WebAppRequestDispatcher.dispatch(WebAppRequestDispatcher.java:530)
at com.ibm.ws.webcontainer.webapp.WebAppRequestDispatcher.forward(WebAppRequestDispatcher.java:176)
at com.ibm.ws.webcontainer.srt.WebAppInvoker.doForward(WebAppInvoker.java:79)
at com.ibm.ws.webcontainer.srt.WebAppInvoker.handleInvocationHook(WebAppInvoker.java:201)
at com.ibm.ws.webcontainer.cache.invocation.CachedInvocation.handleInvocation(CachedInvocation.java:71)
at com.ibm.ws.webcontainer.cache.invocation.CacheableInvocationContext.invoke(CacheableInvocationContext.java:114)
at com.ibm.ws.webcontainer.srp.ServletRequestProcessor.dispatchByURI(ServletRequestProcessor.java:186)
at com.ibm.ws.webcontainer.oselistener.OSEListenerDispatcher.service(OSEListener.java:334)
at com.ibm.ws.webcontainer.http.HttpConnection.handleRequest(HttpConnection.java:56)
at com.ibm.ws.http.HttpConnection.readAndHandleRequest(HttpConnection.java:610)
at com.ibm.ws.http.HttpConnection.run(HttpConnection.java:431)
at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java(Compiled Code))
Haiwei -
How to "auto" generate "Primary Key" in custom table?
Hi Folks,
Requirement:
I need a function module or program that can create automatically a primary key.
Scenario:
I have a program that creates an entries and save it to a custom table at the same time, but a primary key should always be generated respective to the entries saved.
Example:
Material(MATNR) 4001001, Plant(WERKS) XX01, ID[Primary Key-auto generated]
(I'm thinking of a similar concept/logic on how a unique IDOC number is being generated or how SAP standard creates a unique entry)
I try to look for any SAP FM that can generate a PK, but there's no luck.
Thanks.
Regards,
JunHi Keshu and All,
The links are helpful, however:
#1. I don't have authorization to create a new object in transaction SNRO, but the way I see the objects in SNRO is just for defining the length(number of characters) for the ranges that will be use if I'm not mistaken.
#2. FM NUMBER_GET_NEXT - yes it can populate incremental unique entries but it's only occurring at runtime ?? So when the program get terminated it's not being saved nowhere.
So after if I use FM NUMBER_GET_NEXT, I always have to look for all the last primary key in my custom table, then target it as my starting point for creating a new PK. I think this will give a performance issue, any comments?
For better visualization, I have scenario:
1. (ZQ_CREATE_PK) Create unique incremental PK for material, batch, so on..
2. Append line/entries to ZQ_TABLE
3. Repeat #1 and #2
4. User exits the program
5. Back to 1 --> At this point, I need to get the "LATEST" PK then start this as a starting point again to generate PK and append it to ZQ_TABLE
I'm assuming that SAP has other SAP FMs related in creating this scenario. Similar to IDOC # creation..
Thanks. -
HI
I'm going to build a Database to automate center in my university
The Database version is Oracle 10g v2
Which data type of primary key should I user?
I used number in past but I heard there is more efficient data type for this purpose
ThanksBINARY_FLOAT and BINARY_DOUBLE are designed to store floating point numbers. If you are generating synthetic primary keys using a sequence, you are generating integers. It makes no sense from a data modeling perspective to store integer data in floating point fields. And it is exceptionally dangerous if a value gets rounded unexpectedly (floating point numbers lose precision for the trailing bits)
You'll have to clarify for me what "more helpful for indexing" means. As far as storage space goes, there may be some space savings using a BINARY_FLOAT or BINARY_DOUBLE if you have very large primary key values, but there will be a space penalty for most "normal" sequence-generated values, i.e.
SQL> create table x (
2 col1 number,
3 col2 binary_float,
4 col3 binary_double
5 );
Table created.
SQL> insert into x values( 1, 2, 3 );
1 row created.
SQL> select length(col1), length(col2), length(col3) from x;
LENGTH(COL1) LENGTH(COL2) LENGTH(COL3)
1 8 8
SQL> insert into x values (1e20, 1e20, 1e20 );
1 row created.
SQL> select length(col1), length(col2), length(col3) from x;
LENGTH(COL1) LENGTH(COL2) LENGTH(COL3)
1 8 8
21 15 8
SQL> select * from x;
COL1 COL2 COL3
1 2.0E+000 3.0E+000
1.0000E+20 1.0E+020 1.0E+020So it takes 8 times the storage to store a 1 in a BINARY_FLOAT or BINARY_DOUBLE than it does to store that in a NUMBER column. But it takes less space if you're storing values like 1e20 (a 1 with 20 0's). If you're storing values large enough to get the space benefit, however, you're going to have rounding issues that will cause the application not to function as you'd expect which is presumably a much greater problem than a bit of wasted disk space.
Justin -
Composite Primary key & Primary key questions
Background:
1.5 TB data warehouse. All tables use at least a 3 column composite Primary key. Most use 3. col1||col2||col3 to achieve uniqueness.
col1= very low cardinality. 99% of the values are '0'
col2 = high cardinality. (SSN's, loaded monthly)
col3 = low cardinality. (monthly sequence number used for partitioning)
From what I've read, the first column used in a composite primary key also receives its own index. If that is correct, then the primary key being used is losing its effectiveness by putting a very low cardinality column as the first column of the Primary key. By moving col2 to the first position of the composite key, I would be obtaining an index on SSN which would be much more useful. (Please correct me if I'm wrong) Or since the index would be so large anyway, the CBO would just do full table scans which is what I'm trying to get away from.
This Primary key is used to ensure uniqueness during loads. Other than that, it really has no purpose and is never queried by the user. (WHERE col1||col2||col3 = xxxxxxxxx)
As a DBA, I see this massive tablespace for holding the primary keys now reaching in excess of 157 GB and it seems like such a waste of space. The problem I'm running across is how to ensure uniqueness during the loads w/o having to store the unique values. (the 157 GB) If I drop the PK's, then create unique indexes just for the loads, then the unique index would be generated against the entire table, which would take forever.
If you create a local index (what I want in the end) it still has to create the index for all previous partitions (250+ partitions). You can't create a specific 'local' index on a partition. You create a local index on the table and when a new partition is added, the index is then added as well. That's what I want to do with some of my fields like SSN but for loading purposes, this isn't going to help me.
I need a way to ensure uniqueness during a monthly load of a new partition (col1||col2||col3) but w/o having to store these values for eternity. Right now it's the primary key, so it has to be stored. I hope I'm making sense here. Any ideas?I think you need some clarification about the index supporting the primary key.
The primary key is unique - the database will enforce this for you.
All of the columns in the primary key are in the index that enforces the key (not just the first column).
Usually this index is a unique index, but you can have a non-unique index supporting a primary key.
I'm a little confused with some of your other statements
how to ensure uniqueness during the loads w/o having to store the unique valuesIf you don't store the value how do you know it is unique?
Did you mean that you don't want to store the key values in both the table and the index?
You may want to consider making col3 (the partition key) the leading column of the index, so you can create a local (instead of global) PK index.
I wouldn't worry too much about col1 (the column full of mostly zeros) - numbers are stored variable length. A NUMBER(38) that holds a zero takes no more space than a NUMBER(1) that holds a zero. -
Primary key, column, sequence : best practice.
Hi I was wondering when designing table should you limit the length of primary key.
Because if you have limited column length, and your adding and removing items than you have sequence gap, than you will need to resize column length and if their foreign key (resize them in foreign key relationship too) or you need to reset sequence to go back to the maximum (id).
WHat are the benefits and disbenefits of having limited column length. Is their way to restrict the maximum number of items without putting column length in their (inside the database) not the application.
Thanks.Unless you know the exact number of rows your table will have, it is not convenient to limit the size. Now it all depend on what you mean by limiting the size and which column type you are talking about.
Here I have some notes about --> Why is Varchar2 oversizing bad?, where I state this:
Apparently the same space consumption would be the same if a Varchar2(4) is used versus a Varchar2(4000), if you require one byte, then one byte will be allocated, and performance should be the same, but when taking a look at the performance statistics there are some surprises that arise.
When fetching information from Oracle, buffers and fetching structures are being prepared beforehand to be able to manage the maximum column lenght, applications such as toad may run out of memory trying to allocate resources to retrieve the information from an unnecessarily over sized varchar2 column.
The answer to your case is: you should better plan according to your actual requirements, if you oversize columns you will degrade performance and you will have memory issues on the long run. If you under size then you will have problems with maximum capacity in your tables and you will be forced to -most probably- perform online maintenance to your objects to resize them.
~ Madrid
http://hrivera99.blogspot.com/ -
Select-option/Parameter & Primary Key
Dear Abaper,
It this compulsory to have a Table fields define in Parameter/Select-option of Selection screen should be Primary key of respective tables??
and
If we used two different tables having common fields and if common field of Table1 is primary key and Table2 is not a primary key can we used that common field in Parameter/Select-option of selection screen?
Thanks & regards
MahendraHi,
Its not necessary to have fields in parameters/select options to be primary key. It just takes the datatype irrespective of the primary key.
I have written a small example for you:
PARAMETERS: a(18) type c,
b type matnr, "data element
c type mara-matnr. "table-fieldname
These all are one and the same thing. a/b/c will have char 18 data type and length.
Regards
Purnand
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