I have a JPA entity with a composite unique key, and I wrote a scheduler that loads data into the table of this entity. Only that I have an exception when load in in case there is a unique key violation. I want to suppress any unique constraint violation exception from my database and continue the loading of all the other objects. I am using transactions, and I would not want to lock the whole table to verify uniqueness as other users are using it.
I think you can iterate over all objects and wrap the method that load an object into table by a
try{} catch(JPAException exp){}
With this if the exception occurred when load any particular data, the iteration will continue and other objects still be processed.
Related
I have an object in my database that sometimes gets 4-10 updates within 2 seconds this cause a duplicate key value that violates unique constraint to be thrown by my backend (ts-express) and Postgres DB are connected with Typeform. This problem only happens with high request loads, when I send 1 or 2 I have no problem. Any idea?
I am trying to bulk load records from a temp table to table using insert as select stmt and on conflict strategy do update.
I want load as many records as possible, currently if there any any foreign key violations no records get inserted, everything gets rolled back. Is there a way to insert valid records and skip the faulty records.
In https://dba.stackexchange.com/a/46477 I saw a strategy of going with the foreign table in the query to ignore the faulty rows. I don't want to do that too as I may have many foreign keys on that table and it will make my query more complex and table specific. I would like it to be generic.
Sample use case, if have 100 rows in the temp table and suppose row number 5 and 7 are causing insertion failure, I want to insert the rest 98 records and identify which two rows failed.
I want to avoid inserting record by record and catch the error, as it is not efficient. I am doing this whole exercise to avoid loading a table row by row.
Oracle provides support to catch bulk errors at a shot.
Sample https://stackoverflow.com/a/36430893/8575780
https://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:1422998100346727312
I have already explored options loading using copy, it catches not null constraints and other data type errors, but when foreign key violation happens nothing gets committed.
I am looking something closer to what pgloader is doing when it faces error.
https://pgloader.readthedocs.io/en/latest/pgloader.html#batches-and-retry-behaviour
Entity Framework 6 Casscading Deletes and DropForeignKey fails on auto generated constraint name
I've been running into a bit of an issue with Entity Framework and cascade deletes between two tables on several one-to-many relationships.
Initially it looked like the correct path to take was to configure the table mappings with the OnModelCreating method of DbContext turning off cascade delete in a manner such as
modelBuilder.Entity<SourceTable>()
.HasOptional(x => x.NavigationProperty)
.WithOptionalDependent()
.WillCascadeOnDelete(false);
This however did not work throwing an exception stating
Cannot delete or update a parent row: a foreign key constraint fails...
More research lead me to believe that this is because all affected entities must be loaded into the context (eager fetched) so that entity framework may set the FK references to null as part of the transaction. This is not practical for my needs based on the size of the relational graph I'd be dealing with.
My next approach was to modify the Seed method of the Configuration class and run some arbitrary SQL to drop the Foreign Key constraint and re-add it as a ON DELETE SET NULL constaint. This worked in most cases, however one of the consraints has what appears to be an auto generated unpredicatable name that is diffrent on each call of Update-Database. Given that the name can't be predicted the ALTER statments aren't particualr helpful
context.Database.ExecuteSqlCommand(#"ALTER TABLE SourceTable DROP FOREIGN KEY FK_9405957d032142c3a1227821a9ed1fdf;
ALTER TABLE SourceTable
ADD CONSTRAINT FK_ReasonableName
FOREIGN KEY (NavigationProperty_Id) REFERENCES NavigationProperty (Id) ON DELETE SET NULL;");
Finally, I've taken the apprach to use the migration functionality (DbMigration) and override Up method and leveraging the DropForeignKey method along side more explicit SQL to re-add the constraint (EF does not appear to provide a factility to create a ON DELETE SET NULL constraint).
DropForeignKey("SourceTable", "NavigationProperty_Id", "DestinationTable");
Sql("ALTER TABLE SourceTable ADD CONSTRAINT FK_ReasonableName FOREIGN KEY (NavigationProperty_Id) REFERENCES DestinationTable (Id) ON DELETE SET NULL;");
This works great, up until I encounter the constraint with the auto generate name. At this point the DropForeignKey method fails with an exception that is swallowed up by
System.Runtime.Serialization.SerializationException: Type is not resolved for member 'MySql.Data.MySqlClient.MySqlException,MySql.Data...
When dumping the migration to a SQL script file it becomes clear that the DropForeignKey simply generates a FK with a more predictable, non-ambiguous byte stream array.
Is there a proper EF Code First approach to solve the problem of setting FK column values to null when deleting the refrenced row, or am I stuck having to hand code SQL in order to gain this functionality?
I have a SQL server database which have two entities and 4 stored procedures for each entity ( Select, Insert, Update, Delete) and I'm using Entity framework to do data access work in my application. (the application is just for training purpose)
I mapped Insert procedure to an entity and it worked but after that I changed the "Result column binding" to "Id" -identity column-
this caused this exception:
Store update, insert, or delete statement affected an unexpected
number of rows (0). Entities may have been modified or deleted since
entities were loaded. Refresh ObjectStateManager entries.
after searching for a short while I didn't find the reason for it,
then I figured it's what I changed "Result column binding" so I removed it.
Just want to know what is the cause of this exception. what went wrong.
I am trying to use Entity Framework DB first to do quick prototyping of a reporting website for a huge db. The problem is one of the tables doesn't have a key. I got an 'Error 159: EntityType has no key defined'. If I add a key on the model designer, I got 'Error 3024: Must specify mapping for all key properties'. My question is whether there is a way to workaround this WITHOUT adding a key to the table. The table is not in our control.
Huge table which does not have a key? It would not be possible for you or for table owner to search for anything in this table without using full table scan. Also, it is basically impossible to use UPDATE by single row without having primary key.
You really have to either create synthetic key, or ask owner to do that. As a workaround, you might be able to find some existing column (or 2-3 columns) which is unique enough that it can be used as unique key. If it is unique but does not have actual index created, that would be still not good for performance - you should create such index.