I'm converting a Delphi 5 / BDE application to Delphi XE7 / FireDAC. One of my forms has a TFDTable component that points to an Oracle view containing a group by clause in its create statement.
This used to work fine in the BDE application, but with FireDAC I'm getting this error.
ORA-01446: cannot select ROWID from, or sample, a view with DISTINCT,
GROUP BY, etc.
I understand the error I'm getting from Oracle, but I'm not selecting ROWID, FireDAC is! Is there a property in the TFDTable that I can set to prevent it from adding ROWID to the query? If not, how am I supposed to use this view?
FireDAC fetches ROWID because it tries to identify tuples in the resultset for possible updates. For stopping that just enable the ReadOnly option which will properly make the grouped view resultset read only (properly as one cannot just identify particular tuples if they are grouped in a resultset for updating).
The SQL command is generated in TFDPhysCommandGenerator.GenerateSelectTable method, if you wanted to know the source of this problem. There is appended generic unique tuple identifier to the select list according to the ReadOnly property setting (which is ROWID for Oracle DBMS).
Include fiMeta in FetchOptions.Items.
TFDQuery, TFDTable, TFDMemTable, and TFDCommand automatically retrieve
the unique identifying columns (mkPrimaryKeyFields) for the main
(first) table in the SELECT ... FROM ... statements, when fiMeta is
included in FetchOptions.Items. Note:
mkPrimaryKeyFields querying may be time consuming;
the application may need to explicitly specify unique identifying columns, when FireDAC fails to determine them correctly.
To explicitly specify columns, exclude fiMeta from FetchOptions.Items,
and use one of the following options:
set UpdateOptions.KeyFields to a ';' separated list of column names;
include pfInKey into the corresponding TField.ProviderFlags property.
When the application creates persistent fields, then initially
TField.ProviderFlags will be set correctly. After that, automatic
field setup will not happen, when the DB structure or query is
changed. You should manually update ProviderFlags to adjust the column
list. Also, if the primary key consists of several fields, then all of
them must be included into persistent fields. Row Identifying Columns
Alternatively, a row identifying column may be included into the
SELECT list. When FireDAC founds such columns, it will not retrieve
mkPrimaryKeyFields metadata and it will use this column. The supported
DBMSs are the following:
DBMS Row identifying column
Firebird DB_KEY
Informix ROWID
Interbase DB_KEY / RDB$DB_KEY
Oracle ROWID
PostgreSQL OID. The table must be created with OIDs.
SQLite ROWID
Source : http://docwiki.embarcadero.com/RADStudio/XE8/en/Unique_Identifying_Fields_%28FireDAC%29
Related
We are trying to insert records into Oracle table using PutSQL and attribute Obtain Generated Keys is set to true. NiFi DBCPConnectionPool controller service is configured to use Oracle 12c and JDBC is ojdbc8.jar.
The expected value for attribute sql.generated.key should be in number but getting rowid like AAJV6hAAAAAB/qFAAA.
So do we need to do any config settings at Oracle end to return the generated sequence id instead of rowid?
Please note that the same is working as expected for PostgreSQL!
As per this,
the Oracle JDBC driver will not return the value of the id column, but instead it will return the ROW_ID (a pseudo column that identifies a specific row), to allow you to retrieve the value yourself.
Historically the Oracle driver did it this way, because previous Oracle versions didn't have identity columns.
So I have to add a processor to get the generated sequence ID from rowid.
Is it possible to do updates via Resultset to an Oracle view? Asking as my code is giving me insufficient priviledge error when it does the rs.updateRow() call. I have checked and I definitely have access to the table/view.
The code looks like:
white (rs.next()) {
int updateStatus = getPSCforAction(status);
rs.updateInt("SPSC", updateStatus);
rs.updateRow;
}
The SELECT statement changes depends on operation but it will always be querying an Oracle view (and in some cases multiple views). My main question is whether updating via resultSet can be done to an Oracle view (or views)?
To answer your question one must see a definition of you view and a SELECT statament that is used to produce the resulset in your Java code. Without looking at this it is hard to give the answer
Anyway, generar rules and limitations are described in the Oracle Database JDBC Developer's guide:
Result Set Limitations
The following limitations are placed on queries for enhanced result
sets. Failure to follow these guidelines results in the JDBC driver
choosing an alternative result set type or concurrency type.
To produce an updatable result set:
A query can select from only a single table and cannot contain any
join operations.
In addition, for inserts to be feasible, the query must select all
non-nullable columns and all columns that do not have a default value.
A query cannot use SELECT * . However, there is a workaround for this.
A query must select table columns only.
It cannot select derived columns or aggregates, such as the SUM or MAX
of a set of columns.
To produce a scroll-sensitive result set:
A query cannot use SELECT *. However, there is a workaround for this.
A query can select from only a single table.
Scrollable and updatable result sets cannot have any column as Stream.
When the server has to fetch a Stream column, it reduces the fetch
size to one and blocks all columns following the Stream column until
the Stream column is read. As a result, columns cannot be fetched in
bulk and scrolled through.
They vaguely write that:
A query can select from only a single table and cannot contain any
join operations.
Could be that they mean "exlusively from tables, but not views", but also they could mean: "from tables and views", nobody knows, one must test this.
Another possible problem - your view may not be updatable, that is it doesn't conform to the following rules:
Notes on Updatable Views The following notes apply to updatable views:
An updatable view is one you can use to insert, update, or delete base
table rows. You can create a view to be inherently updatable, or you
can create an INSTEAD OF trigger on any view to make it updatable.
To learn whether and in what ways the columns of an inherently
updatable view can be modified, query the USER_UPDATABLE_COLUMNS data
dictionary view. The information displayed by this view is meaningful
only for inherently updatable views. For a view to be inherently
updatable, the following conditions must be met:
Each column in the view must map to a column of a single table. For
example, if a view column maps to the output of a TABLE clause (an
unnested collection), then the view is not inherently updatable.
The view must not contain any of the following constructs:
A set operator
A DISTINCT operator
An aggregate or analytic function
A GROUP BY, ORDER BY, MODEL, CONNECT BY, or START WITH clause
A collection expression in a SELECT list
A subquery in a SELECT list
A subquery designated WITH READ ONLY Joins, with some exceptions, as
documented in Oracle Database Administrator's Guide
In addition, if an
inherently updatable view contains pseudocolumns or expressions, then
you cannot update base table rows with an UPDATE statement that refers
to any of these pseudocolumns or expressions.
If you want a join view to be updatable, then all of the following
conditions must be true:
The DML statement must affect only one table underlying the join.
For an INSERT statement, the view must not be created WITH CHECK
OPTION, and all columns into which values are inserted must come from
a key-preserved table. A key-preserved table is one for which every
primary key or unique key value in the base table is also unique in
the join view.
For an UPDATE statement, the view must not be created WITH CHECK
OPTION, and all columns updated must be extracted from a key-preserved
table.
For a DELETE statement, if the join results in more than one
key-preserved table, then Oracle Database deletes from the first table
named in the FROM clause, whether or not the view was created WITH
CHECK OPTION.
I am trying to load the tables into oracle in-memory database. I have enable the tables for INMEMORY by using sql+ command ALTER TABLE table_name INMEMORY. The table also contains data i.e. the table is populated. But when I try to use the command SELECT v.owner, v.segment_name name, v.populate_status status from v$im_segments v;, it shows no rows selected.
What can be the problem?
Have you considered this?
https://docs.oracle.com/database/121/CNCPT/memory.htm#GUID-DF723C06-62FE-4E5A-8BE0-0703695A7886
Population of the IM Column Store in Response to Queries
Setting the INMEMORY attribute on an object means that this object is a candidate for population in the IM column store, not that the database immediately populates the object in memory.
By default (INMEMORY PRIORITY is set to NONE), the database delays population of a table in the IM column store until the database considers it useful. When the INMEMORY attribute is set for an object, the database may choose not to materialize all columns when the database determines that the memory is better used elsewhere. Also, the IM column store may populate a subset of columns from a table.
You probably need to run a select against the date first
I need to create a sequence whose value is going to be read by call to .NEXTVAL in PL/SQL code and saved in more then one record of a specific table column, so my design doesn't require to define a PK on the aforementioned column.
I cannot find out how to edit the sequence tab in Oracle Data Modeler (I'm on version 4.1.1) when the PK checkbox is not selected (all the sequence related fields are disabled).
Any idea?
In the relational model, choose your DB and within that you will find sequence as an item to create. You can also create other types of object here.
I have 62 columns in a table under SQL 2005 and LINQ to SQL doesn't handle the updates though the reading would work just fine, I tried re-adding the table to the model, created a new data model but nothing worked, I'm guessing I've hit the maximum number of columns limit on an object, can anyone explain that ?
I suspect there is some issue with an identity or timestamp column (something autogenerated on the SQL server). Make sure that any column that is autogenerated is marked that way in the model. You might also want to look at how it is handling concurrency. If you have triggers that update any values on the row after it is updated (changing values) and it is checking all columns on updates, this would cause the update to fail. Typically I create my tables with a timestamp column -- LINQ2SQL picks this up when I generate the model and uses it alone for concurrency.
Solved, either one of the following two
-I'm using a UniqueIdentifier column that was not set as Primary key
-Set Unique ID primary key, checked the properties of the same column in Server Explorer and it was still not showing as Primary key, refreshed the connection,dropped the same table on the model and voila.
So I assume I made a change to my model some time before, deleted the table from the model and added the same from the Server explorer without refreshing the connection and it never used to work.
Question is, does VS Server Explorer maintain it's own table schema and requires connection refresh everytime a change is made in the database ?
There is no limit to the number of columns LINQ to SQL will handle.
Have you got other tables updating successfully?
What else is different about how you are accessing the table content?