Indexing foreign key
Hello there,
Should i index all foreign keys in the table if there are more then 20 foreign keys
please reply ASAP.
If there is DML activity on the related parent tables you need to. Because updating the parent table causes the child table to be locked if there is no index on the foreign key.
By the way, if you need ASAP answers, do not use this forum or start paying to the respondents.
Similar Messages
-
Question on indexing foreign key for replicated table
Hi everybody,
I have 2 tables with following script
create table
parent(parent_id number(2) not null,
parent_name varchar(20),
constraint parent_pk primary key(parent_id))
create table child(child_id number(2) not null,
parent_id number(2) not null,
child_name varchar2(20),
constraint pk_child primary key(child_id,parent_id),
constraint fk_child foreign key (parent_id) references parenr(parent_id)
I want to replicate them and I know to replicate these 2 tables i should add them to my replication group, my question is that the child_id has foreign key so as below link says
http://dbataj.blogspot.com/2007/11/advance-replication-part-ii-master.html
I should put an index on the foreign key.What type of index should it be and is the following script correct for my purpose?
CREATE BITMAP
INDEX "fk_child"
ON child ("PARENT_ID")
TABLESPACE "USERS"
I would appreciate your help in advance.
MeryA bitmap index is almost certainly not the sort of index you'd want to create. You would normally want just a normal index, i.e.
CREATE INDEX fk_child
ON child( parent_id )on the master database just to support normal DML operations (otherwise, deleting a row from the parent table requires doing a full table scan on the child table to see if there are any orphaned child records).
If you are trying to set up a multi-master replication environment, you would also need to replicate this index, since you'll want to support basic DML on both nodes.
Justin -
Hello all,
I have on table with a foreign key.
When I do a select statement with a WHERE clause containing the Foreign key, the table is fully scanned.
Can I index the foreign key in this case, it's an integer value (from 1 to 100 values) ? What index should i use ?More info:
http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:292016138754
http://tkyte.blogspot.com/2009/10/httpasktomoraclecomtkyteunindex.html -
Necessary to have foreign keys ?
Dear All,
We have a oracle database, in which there is no foreign key constraints defined. But we are able to join the tables with the appropriate columns and getting the output of the query perfectly.
Now, is that mandatory to have foreign key columns defined or the current design is fine. Please help me in this, by discussing the advantages and disadvantages.
Thanks in advance.
Anand.Best practice would absolutely be to have foreign keys in an OLTP system.
Without foreign keys, you are guaranteed to have data that violates referential integrity eventually. Unless you happen to be lucky enough to work on an application that will never have bugs, you need Oracle to enforce referential integrity.
Without foreign keys, your data model is much harder to understand. That means that when new developers come on the project, when people want to point various tools at the database, etc. those people and tools will not be able to use foreign keys to determine how the tables relate. That inevitably means that it will take them far longer to get up to speed and they are far more likely to make errors. If you ever point an automated tool at the database to generate an ERD, that tool will be nearly useless since it can't figure out how the tables relate.
Without foreign keys, you're depriving the optimizer of information that may allow it to generate better plans.
Yes, you need to index foreign keys in the child table, but you almost certainly need these indexes for queries anyway. Other than that, there are really no downsides. Yes, Oracle has to do a minute amount of work to verify the foreign key during DML, but it will be far more efficient for Oracle to do this than for your application to do it.
Justin -
Can we associate index with foreign key?
hello
i have searched and could not find the answer to the above;
i have a foreign key constraint on the tables; i added an index on that column as well;
however when i query the all_constraints, under index_name for this foreign constraint there is nothing; only when i have PK/UK i case see indexes associated with them;
will then oracle still associate my index with the FK constrained column? or i need to excplicity associate it with the foreign key column? if so, how to do that?
thx
rgdsHi,
UserMB wrote:
i have a foreign key constraint on the tables; i added an index on that column as well;It helps if you give a specific example, such as:
"I have a foreign key constraint, where emp.deptno references dept.deptno. (Deptno is the primary key of dept.) I created an index called emp_deptno_idx on emp.deptno as well."
however when i query the all_constraints, under index_name for this foreign constraint there is nothing; only when i have PK/UK i case see indexes associated with them;Not all indexes are associated with a constraint. In the example above, you wouldn't expect to see anything about the index emp_demptno_idx in all_constraints or in all_cons_columns.
will then oracle still associate my index with the FK constrained column? or i need to excplicity associate it with the foreign key column? if so, how to do that?In the situation above, Oracle will still use the index when the optimizer thinks it will help. You don't have to do anything else. -
Creation of Index for Primary & Foreign Key required?
hi,
i would like to find out if a column is defined as the primary key, do i need to create a separate index for it? or defining a primary key will tell the db to automatically create an index for it?
does foreign key have the same behavior as the primary key constraint?
thanks!i would like to find out if a column is defined as the primary key, do i need to create a separate index for it? No
or defining a primary key will tell the db to automatically create an index for it? Yes
See
http://download-uk.oracle.com/docs/cd/B10501_01/appdev.920/a96590/adg05itg.htm#7265
does foreign key have the same behavior as the primary key constraint?No. See http://download-uk.oracle.com/docs/cd/B10501_01/appdev.920/a96590/adg05itg.htm#1574 -
I am running an SQL(CE) script to create a DB. All script commands succeed, but the DB get "broken" after creating the last costaint: after running the script, viewing table properties of Table2 and clicking on "Manage relations" gives the following error: Unable to create foreign key: InvalidArgument=Value of '0' is not valid for 'index'. Parameter name: index. Wondering what does that refer to...
Here it is the script. Please note that no error is thrown by running the following queries (even from code that passing the queries by hand, one-by-one to sql server management studio).
CREATE TABLE [table1] (
[id_rubrica] numeric(18,0) NOT NULL
, [id_campo] numeric(18,0) NOT NULL
, [nome] nvarchar(100) NOT NULL
GO
ALTER TABLE [table1] ADD PRIMARY KEY ([id_rubrica],[id_campo]);
GO
CREATE UNIQUE INDEX [UQ__m_campi] ON [table1] ([id_campo] Asc);
GO
CREATE TABLE [table2] (
[id_campo] numeric(18,0) NOT NULL
, [valore] nvarchar(4000) NOT NULL
GO
ALTER TABLE [table2] ADD PRIMARY KEY ([id_campo],[valore]);
GO
ALTER TABLE [table2] ADD CONSTRAINT [campo_valoriFissi] FOREIGN KEY ([id_campo]) REFERENCES [table1]([id_campo]);
GO
Sid (MCP - http://www.sugata.eu)I know this is kind of old post, but did this realy solved your problem?
I'm getting this same error message after adding a FK constraint via UI on VS2008 Server Explorer.
I can add the constraint with no errors, but the constraint is not created on the DataSet wizard (strongly typed datasets on Win CE 6) and when I click "Manage Relations" on the "Table Properties" this error pop out:
"InvalidArgument=Value or '0' is not valid for 'index'.
Parameter name: index"
Even after vreating my table with the relation in SQL the same occurs:
CREATE TABLE pedidosRastreios (
idPedidoRastreio INT NOT NULL IDENTITY PRIMARY KEY,
idPedido INT NOT NULL CONSTRAINT FK_pedidosRastreios_pedidos REFERENCES pedidos(idPedido) ON DELETE CASCADE,
codigo NVARCHAR(20) NOT NULL -
Publish: dropping index when it is used for foreign key constraint enforcement
Hi,
I'm trying to update a target schema from a reference database via Publish. Among the changes to apply, there's an index that needs to be dropped. Since it's linked to a foreign key constraint, it cannot be deleted unless the foreign key is temporarily dropped
(I saw somewhere that disabling the foreign key should be enough but it doesn't seem to work either).
Since there are other changes to be made on the same table, this foreign key also has to be dropped before the script can delete the table and re-create it. This part of the script is correctly generated. The problem is that this part appears after the 'DROP
INDEX' instruction.
So when generating the update script, SSDT tries to drop the index BEFORE dropping the foreign key. And I can't drop the foreign key in my custom pre-deployment script, otherwise the update script would fail when trying to delete it again.
Shouldn't SSDT be smart enough to drop the constraint before the index? Is it a bug or did I forget to set an option? If it's not a bug, what can I do apart from doing it manually?
Thank you for your helpHi Elsa,
That sounds like a bug. Could you please file a Connect issue for this at
https://connect.microsoft.com/SQLServer/feedback/CreateFeedback.aspx using the category "Developer Tools (SSDT, BIDS, etc.)"? We're trying to track all bugs through
Connect so that you can tell when we have fixed the issue and we can request more information.
A workaround for this issue might be to write a pre-deployment script for your project to drop the foreign key prior to deployment. A pre-deployment script can be added to your project by right-clicking on the
project in solution explorer and then clicking on Add > Script... and selecting Pre-Deployment Script from the list.
Thanks! -
Storage for Foreign Keys and Function based indexes
This may well be the silliest question of the day, but is it possible to specify the storage for a Foreign key or a function based index? I'm not even sure that it would make sense.
Well, a foreign key constraint is not a segment, nor is any other type of constraint. However, a function-based index is a segment, just like any other index. So, in that case, specify a tablespace, just like you would with any other index.
Something like this:
create index my_fbi on my_tab(upper(last_name)) tablespace my_index_tablespace;
-Mark
Message was edited by:
mbobak
Fixed minor typo. -
We have doubt in definition of "Foreign Key Indexe",
Please give us a clear definition.
Thanks in advance
SoheilWe have doubt in definition of "Foreign Key Indexe",
Please give us a clear definition.
Thanks in advance
Soheil -
In our table:
Table Name:
STATUS
Columns:
STATUSID NUMBER (PKEY)
USERID NUMBER (FKEY)
PATIENTNAME VARCHAR(30)
STATUS_DATE DATE
CREATE_DATE DATE
CHSTATUS VARCHAR(30)
PAYER_STATUS VARCHAR(30)
CHARGE_AMOUNT DOUBLE
INS_AMOUNT DOUBLE
X12IN CLOB
We have a foreign key on the USERID column. And this column appears in the WHERE clause always.
I wanted to know in addition to the foriegn key constraint, putting an INDEX on the USERID column will help query performance?
Generally speaking:
I wanted to know whether in oracle putting a foreign key constraint on a column creates an INDEX automatically or do I put the index specifically besides the FOREIGN key.
Thanks in Advance,
Rumpa GiriHello
Oracle does NOT create an index when you put a foreign key constraint on a column, so you need to create one if you want one.
Have a look at this discussion on asktom to understand when and why indexes on foreign keys are a good idea.
If your query that uses USERID in the where caluse returns a small number of rows in proportion to the number of rows in the table, adding an index could well help with query performance....but as always, it's best to benchmark it and get some stats that you can then use to make an informed choice.
HTH
David
Message was edited by:
david_tyler -
Nobody can help me? What is Foreign key indexes?
We have doubt in definition of "Foreign Key Indexe",
Please give us a clear definition.
Thanks in advance
SoheilWe have doubt in definition of "Foreign Key Indexe",
Please give us a clear definition.
Thanks in advance
Soheil -
Binding for table produces list for other tables using foreign key and crea
Using
software Jdev 11G, WLS 11G, Oracle DB 11G, Windows Vista platform
technology EJB 3.0, jspx, backing beans, session bean
I cannot create a namedquery on my secondary table. The method for the column uses the entity object rather than the name and value of the column.
For instance,
(Coketruck) table has inventory records(Products) table
Coketruck has one to many to the Products table
Products has a many to one to the Coketruck
I need to return the products from the product table based on the CokeTruck but I cannot create a namedQuery because the method in the Product table is an entity object type instead of a long that I can use to look up all the products based off the column truck_id.
This is what I was expecting…
Private Long truckId;
public Long getTruckId() {
return truckId;
public void setTruckId (Long truckId) {
this. truckId = truckId;
Instead this is what I have…
@ManyToOne
@JoinColumn(name = "TRUCK_ID")
private Coketruck coketruck;
this. coketruck = coketruck
public Coketruck getCoketruck() {
return coketruck;
public void set Coketruck (Coketruck coketruck) {
this. coketruck = coketruck;
How do I do a query on the Product table to return all the products that are in the coketruck?
If I do the following it expects for me to pass the Entity Object which I cannot use as search criteria for my find method.
@NamedQuery(name = "Products.findById", query = "select o from Products o where o.truckId = :truckId")
On a different note but the same song…
I noticed that when I look at my Session Bean Data Contols that the coketruck already has a list of the products. I have created a jsp page with a backing bean and have been able to use the namedquery on the coketruck entity to retrieve the productList. Unfortunately I need to sort the products by type and was also not able to find where to perform the work to be able to iterate through the productList to get my desired display. Therefore I started looking at doing another namedquery that would only retrieve the product_type ordering by the truckId.
Seems I have come full circle… I don’t care what method I have to use to get the info back.
Any help is greatly appreciated!user9005175 wrote:
Hi!
I work on an application wich uses a shopping cart stored in a database. The shopping cart uses two tables:
CART: Holds information common for one shopping cart: the user it is connected to etc.
- Primary key: CART_ID
CART_ROW: One row in the cart, e.g. one new product to buy.
- Primary key: ROW_ID
- Foreign key: CART_ROW.CART_ID references CART.CART_ID
From the code the rows in the cart are collected per cart, as is modelled by the foreign key. There exists one more relationship, which we use in the code, but which is not modelled by a foreign key in the database. One row can be dependent on another row, which makes the other row a parent.
CART_ROW has a column PARENT_ID which references CART_ROW.ROW_ID.
Should we add a foreign key for PARENT_ID? Or are there any questions to consider when it is a foreign key to the same table?
I suggest to add foreign key it wont harm the performance (except while on insert when there would be validation for the foreign key). But it would prevent users to insert wrong/corrupt data either through code or directly by loggin in the database.
A while ago we added indexes, both on ROW_ID and on PARENT_ID. Could the index on PARENT_ID have been harmful, since there is no foreign key?
Index on parent_id would only be harmful if you do not make use of index after creating it (i.e. there is no query which make use of this index).
And if you decide to have a foreign key on parent_id then I suggest to have index too on parent_id as it would be helpful atleast when you delete any record in this table.
Best regards! -
Hi All,
Let's picture that I have a GW service called Search Helps and within that service I have a PersonalAreas Entity Set which acts as a search help for drop down fields effectively that need to select a Personal Area. I have 3 properties, with Personal Area Id and Company Code being the keys, and the text for Personal Area being the 3rd and last property. You really need to filter PersonalAreas by Company Code otherwise it's a fairly useless result set.
Now within a different GW service, I have an entity called Position which has a single key of PositionId. There is also a a property of company code on this Position.
Now rather than asking the UI developer to get the Company code value and filter PersonalAreas with it directly, I thought it would be nicer for the UI developer just to use the navigation from a specific Position to PossiblePersonalAreas. e.g. Positions('123')/PossiblePersonalAreas returns the entity set of PersonalAreas filtered by the Position's Company Code.
So with that in mind, I add the external model reference pointing at the search helps service; then create an external association via the sneaky External Associations Editor button (that doesn't appear on the Wizard just to confuse you), and set up my Dependent entity to point at the Search Helps PersonalAreas entity.
At this point I really want to tie the Position's Company Code to the PersonalAreas Company Code, but all I can do is set up a referential constraint of PositionId to CompanyCode or have no referential constraint at all (note - in my example I added the referential constraint as there is an issue with navigation keys being provided to external associations from what I can tell - more about this below).
So, without any other option, I go into my GetEntitySet method of PersonalAreas and write something like the following:
CASE iv_source_name.
WHEN 'Position'.
READ TABLE it_filter_select_options ASSIGNING <filter> INDEX 1.
CHECK sy-subrc = 0.
READ TABLE <filter>-select_options assigning <select_option> INDEX 1.
CHECK sy-subrc = 0.
position_id = <select_option>-low.
* Get company code for position
TRY.
CREATE OBJECT o_position
EXPORTING
i_position_id = position_id.
o_position->get_cost_centre_information(
IMPORTING
e_company_code = company_code
CATCH zcx_hr_object.
ENDTRY.
endcase.
* Continue with retrieving PersonalAreas for given Company Code
<Remaining code not shown>
e.g. I have to assume CompanyCode is actually "Position Id" when the source of this call is from Position (I could also look at the navigation to find this has come from Position but if you're wondering, unfortunately for external associations, the key is not included in this for some reason but the same followup logic of reloading the object would be required).
So the question I'm hoping the answer to is Yes is: Am I missing something in my understanding here?
Thanks,
Matt
Edit since posting and playing around a bit more: Thinking about this further - it's unfortunate, but the navigation property in odata really implies the dependent entity has knowledge of the principal entity and realistically must know how to instantiate it if it needs to get data based on one of the properties.
Now while I'm fine with that (sort of) I think it's wrong that the dependent entity needs to have the required key properties to hold the principal entities as it makes something like a generic search help impossible to do with navigation - Maybe I just need to be done with that and expect filters to be used by UI programmers to find foreign key'ed entities....Hi Matt,
I'm not surprised that you have an issue with this. One bugbear I have with Gateway is that for some reason the designers don't think any context beyond the immediate preceding navigation node is important. They don't support this within the same service,so it's hardly likley to work in a service reference.
I may be wrong but I don't think GW is OData compliant in this respect. If I have the navigation path /blindservice/FromHereSet(1)/ToAPoints(22)/ToBPoints, it's rather restrictive to say I cannot see the initial key of '1' in the path when I am trying to resolve 'ToBPoints'. If that value - where I started - is key to the context, I have to know it.
Currently the only way to access this context is to embed the 'key history' in the intermediate entities, i.e. /blindservice/FromHereSet(1)/ToAPoints(1,22)/ToBPoints. In my view that is corrupting the URl to suit the limitations of the SAP OData implementation. What's even more confusing/frustrating is that the technical request context appears to be able to store the stacked navigation keys but doesn't make use of this design.
I feel your pain
Ron. -
Caching problem w/ primary-foreign key mapping
I have seen this a couple of times now. It is not consistent enough to
create a simple reproducible test case, so I will have to describe it to you
with an example and hope you can track it down. It only occurs when caching
is enabled.
Here are the classes:
class C1 { int id; C2 c2; }
class C2 { int id; C1 c1; }
Each class uses application identity using static nested Id classes: C1.Id
and C2.Id. What is unusual is that the same value is used for both
instances:
int id = nextId();
C1 c1 = new C1(id);
C2 c2 = new C2(id);
c1.c2 = c2;
c2.c1 = c1;
This all works fine using optimistic transactions with caching disabled.
Although the integer values are the same, the oids are unique because each
class defines its own unique oid class.
Here is the schema and mapping (this works with caching disabled but fails
with caching enabled):
table t1: column id integer, column revision integer, primary key (id)
table t2: column id integer, column revision integer, primary key (id)
<jdo>
<package name="test">
<class name="C1" objectid-class="C1$Id">
<extension vendor-name="kodo" key="jdbc-class-map" value="base">
<extension vendor-name="kodo" key="table" value="t1"/>
</extension>
<extension vendor-name="kodo" key="jdbc-version-ind"
value="version-number">
<extension vendor-name="kodo" key="column" value="revision"/>
</extension>
<field name="id" primary-key="true">
<extension vendor-name="kodo" key="jdbc-field-map" value="value">
<extension vendor-name="kodo" key="column" value="id"/>
</extension>
</field>
<field name="c2">
<extension vendor-name="kodo" key="jdbc-field-map" value="one-one">
<extension vendor-name="kodo" key="column.id" value="id"/>
</extension>
</field>
</class>
<class name="C2" objectid-class="C2$Id">
<extension vendor-name="kodo" key="jdbc-class-map" value="base">
<extension vendor-name="kodo" key="table" value="t2"/>
</extension>
<extension vendor-name="kodo" key="jdbc-version-ind"
value="version-number">
<extension vendor-name="kodo" key="column" value="revision"/>
</extension>
<field name="id" primary-key="true">
<extension vendor-name="kodo" key="jdbc-field-map" value="value">
<extension vendor-name="kodo" key="column" value="id"/>
</extension>
</field>
<field name="c1">
<extension vendor-name="kodo" key="dependent" value="true"/>
<extension vendor-name="kodo" key="inverse-owner" value="c2"/>
<extension vendor-name="kodo" key="jdbc-field-map" value="one-one">
<extension vendor-name="kodo" key="table" value="t1"/>
<extension vendor-name="kodo" key="ref-column.id" value="id"/>
<extension vendor-name="kodo" key="column.id" value="id"/>
</extension>
</field>
</class>
</package>
</jdo>
Because the ids are known to be the same, the primary key values are also
used as foreign key values. Accessing C2.c1 is always non-null when caching
is disabled. With caching is enabled C2.c1 is usually non-null but sometimes
null. When it is null we get warnings about dangling references to deleted
instances with id values of 0 and other similar warnings.
The workaround is to add a redundant column with the same value. For some
reason this works around the caching problem (this is unnecessary with
caching disabled):
table t1: column id integer, column id2 integer, column revision integer,
primary key (id), unique index (id2)
table t2: column id integer, column revision integer, primary key (id)
<jdo>
<package name="test">
<class name="C1" objectid-class="C1$Id">
<extension vendor-name="kodo" key="jdbc-class-map" value="base">
<extension vendor-name="kodo" key="table" value="t1"/>
</extension>
<extension vendor-name="kodo" key="jdbc-version-ind"
value="version-number">
<extension vendor-name="kodo" key="column" value="revision"/>
</extension>
<field name="id" primary-key="true">
<extension vendor-name="kodo" key="jdbc-field-map" value="value">
<extension vendor-name="kodo" key="column" value="id"/>
</extension>
</field>
<field name="c2">
<extension vendor-name="kodo" key="jdbc-field-map" value="one-one">
<extension vendor-name="kodo" key="column.id" value="id2"/>
</extension>
</field>
</class>
<class name="C2" objectid-class="C2$Id">
<extension vendor-name="kodo" key="jdbc-class-map" value="base">
<extension vendor-name="kodo" key="table" value="t2"/>
</extension>
<extension vendor-name="kodo" key="jdbc-version-ind"
value="version-number">
<extension vendor-name="kodo" key="column" value="revision"/>
</extension>
<field name="id" primary-key="true">
<extension vendor-name="kodo" key="jdbc-field-map" value="value">
<extension vendor-name="kodo" key="column" value="id"/>
</extension>
</field>
<field name="c1">
<extension vendor-name="kodo" key="dependent" value="true"/>
<extension vendor-name="kodo" key="inverse-owner" value="c2"/>
<extension vendor-name="kodo" key="jdbc-field-map" value="one-one">
<extension vendor-name="kodo" key="table" value="t1"/>
<extension vendor-name="kodo" key="ref-column.id" value="id2"/>
<extension vendor-name="kodo" key="column.id" value="id"/>
</extension>
</field>
</class>
</package>
</jdo>
Needless to say, the extra column adds a lot of overhead, including the
addition of a second unique index, for no value other than working around
the caching defect.Tom-
The first thing that I think of whenever I see a problem like this is
that the equals() and hashCode() methods of your application identity
classes are not correct. Can you check them to ensure that they are
written in accordance to the guidelines at:
http://docs.solarmetric.com/manual.html#jdo_overview_pc_identity_application
If that doesn't help address the problem, can you post the code for your
application identity classes so we can double-check, and we will try to
determine what might be causing the problem.
In article <[email protected]>, Tom Landon wrote:
I have seen this a couple of times now. It is not consistent enough to
create a simple reproducible test case, so I will have to describe it to you
with an example and hope you can track it down. It only occurs when caching
is enabled.
Here are the classes:
class C1 { int id; C2 c2; }
class C2 { int id; C1 c1; }
Each class uses application identity using static nested Id classes: C1.Id
and C2.Id. What is unusual is that the same value is used for both
instances:
int id = nextId();
C1 c1 = new C1(id);
C2 c2 = new C2(id);
c1.c2 = c2;
c2.c1 = c1;
This all works fine using optimistic transactions with caching disabled.
Although the integer values are the same, the oids are unique because each
class defines its own unique oid class.
Here is the schema and mapping (this works with caching disabled but fails
with caching enabled):
table t1: column id integer, column revision integer, primary key (id)
table t2: column id integer, column revision integer, primary key (id)
<jdo>
<package name="test">
<class name="C1" objectid-class="C1$Id">
<extension vendor-name="kodo" key="jdbc-class-map" value="base">
<extension vendor-name="kodo" key="table" value="t1"/>
</extension>
<extension vendor-name="kodo" key="jdbc-version-ind"
value="version-number">
<extension vendor-name="kodo" key="column" value="revision"/>
</extension>
<field name="id" primary-key="true">
<extension vendor-name="kodo" key="jdbc-field-map" value="value">
<extension vendor-name="kodo" key="column" value="id"/>
</extension>
</field>
<field name="c2">
<extension vendor-name="kodo" key="jdbc-field-map" value="one-one">
<extension vendor-name="kodo" key="column.id" value="id"/>
</extension>
</field>
</class>
<class name="C2" objectid-class="C2$Id">
<extension vendor-name="kodo" key="jdbc-class-map" value="base">
<extension vendor-name="kodo" key="table" value="t2"/>
</extension>
<extension vendor-name="kodo" key="jdbc-version-ind"
value="version-number">
<extension vendor-name="kodo" key="column" value="revision"/>
</extension>
<field name="id" primary-key="true">
<extension vendor-name="kodo" key="jdbc-field-map" value="value">
<extension vendor-name="kodo" key="column" value="id"/>
</extension>
</field>
<field name="c1">
<extension vendor-name="kodo" key="dependent" value="true"/>
<extension vendor-name="kodo" key="inverse-owner" value="c2"/>
<extension vendor-name="kodo" key="jdbc-field-map" value="one-one">
<extension vendor-name="kodo" key="table" value="t1"/>
<extension vendor-name="kodo" key="ref-column.id" value="id"/>
<extension vendor-name="kodo" key="column.id" value="id"/>
</extension>
</field>
</class>
</package>
</jdo>
Because the ids are known to be the same, the primary key values are also
used as foreign key values. Accessing C2.c1 is always non-null when caching
is disabled. With caching is enabled C2.c1 is usually non-null but sometimes
null. When it is null we get warnings about dangling references to deleted
instances with id values of 0 and other similar warnings.
The workaround is to add a redundant column with the same value. For some
reason this works around the caching problem (this is unnecessary with
caching disabled):
table t1: column id integer, column id2 integer, column revision integer,
primary key (id), unique index (id2)
table t2: column id integer, column revision integer, primary key (id)
<jdo>
<package name="test">
<class name="C1" objectid-class="C1$Id">
<extension vendor-name="kodo" key="jdbc-class-map" value="base">
<extension vendor-name="kodo" key="table" value="t1"/>
</extension>
<extension vendor-name="kodo" key="jdbc-version-ind"
value="version-number">
<extension vendor-name="kodo" key="column" value="revision"/>
</extension>
<field name="id" primary-key="true">
<extension vendor-name="kodo" key="jdbc-field-map" value="value">
<extension vendor-name="kodo" key="column" value="id"/>
</extension>
</field>
<field name="c2">
<extension vendor-name="kodo" key="jdbc-field-map" value="one-one">
<extension vendor-name="kodo" key="column.id" value="id2"/>
</extension>
</field>
</class>
<class name="C2" objectid-class="C2$Id">
<extension vendor-name="kodo" key="jdbc-class-map" value="base">
<extension vendor-name="kodo" key="table" value="t2"/>
</extension>
<extension vendor-name="kodo" key="jdbc-version-ind"
value="version-number">
<extension vendor-name="kodo" key="column" value="revision"/>
</extension>
<field name="id" primary-key="true">
<extension vendor-name="kodo" key="jdbc-field-map" value="value">
<extension vendor-name="kodo" key="column" value="id"/>
</extension>
</field>
<field name="c1">
<extension vendor-name="kodo" key="dependent" value="true"/>
<extension vendor-name="kodo" key="inverse-owner" value="c2"/>
<extension vendor-name="kodo" key="jdbc-field-map" value="one-one">
<extension vendor-name="kodo" key="table" value="t1"/>
<extension vendor-name="kodo" key="ref-column.id" value="id2"/>
<extension vendor-name="kodo" key="column.id" value="id"/>
</extension>
</field>
</class>
</package>
</jdo>
Needless to say, the extra column adds a lot of overhead, including the
addition of a second unique index, for no value other than working around
the caching defect.
Marc Prud'hommeaux [email protected]
SolarMetric Inc. http://www.solarmetric.com
Maybe you are looking for
-
High Quality Import settings not working
Hi, Running iTunes 6.0.4 for Windows and have completely removed and reinstalled it to try to resolve this problem. When I go to the Importing preferences and I try to selet a "Custom..." bit rate....it always defaults back to 128kpbs. I've tried set
-
Request vs Actual Start Date in Scheduler Jobs
Hi, I want to run a PL/SQL block, all days, at 1:00 AM I've defined the following scheduler job, in a new (and empty) Job Class: <font face="Courier New"> SQL> select job_name, repeat_interval, job_class, job_priority from dba_scheduler_jobs where jo
-
Wait Activity not waking-up on time
Hi, We have several flows that utilise Wait Activities to wait until a specific time. Occassionally we have noticed that the flow remains within the Wait Activity after the wait time has passed. A specific example occurred today where at "2009/10/20
-
MacBookPro power adapter for UK and Europe
I am going to be spending a semester in the UK and was wondering where I could find a adapter for my power cable.
-
I bought Adobe Acrobat Pro XI but installing software does not recognize Acrobat 7.0 Pro for upgrade
I bought Adobe Acrobat Pro XI but installing software does not recognize Acrobat 7.0 Pro for upgrade