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Why is the row id increased by one (or more) even after one (or more) ConstraintViolationException? [duplicate]

I have got a table with auto increment primary key. This table is meant to store millions of records and I don't need to delete anything for now. The problem is, when new rows are getting inserted, because of some error, the auto increment key is leaving some gaps in the auto increment ids.. For example, after 5, the next id is 8, leaving the gap of 6 and 7. Result of this is when I count the rows, it results 28000, but the max id is 58000. What can be the reason? I am not deleting anything. And how can I fix this issue.
P.S. I am using insert ignore while inserting records so that it doesn't give error when I try to insert duplicate entry in unique column.

This is by design and will always happen.
Why?
Let's take 2 overlapping transaction that are doing INSERTs
Transaction 1 does an INSERT, gets the value (let's say 42), does more work
Transaction 2 does an INSERT, gets the value 43, does more work
Then
Transaction 1 fails. Rolls back. 42 stays unused
Transaction 2 completes with 43
If consecutive values were guaranteed, every transaction would have to happen one after the other. Not very scalable.
Also see Do Inserted Records Always Receive Contiguous Identity Values (SQL Server but same principle applies)

You can create a trigger to handle the auto increment as:
CREATE DEFINER=`root`#`localhost` TRIGGER `mytable_before_insert` BEFORE INSERT ON `mytable` FOR EACH ROW
BEGIN
SET NEW.id = (SELECT IFNULL(MAX(id), 0) + 1 FROM mytable);;
END

This is a problem in the InnoDB, the storage engine of MySQL.
It really isn't a problem as when you check the docs on “AUTO_INCREMENT Handling in InnoDB” it basically says InnoDB uses a special table to do the auto increments at startup
And the query it uses is something like
SELECT MAX(ai_col) FROM t FOR UPDATE;
This improves concurrency without really having an affect on your data.
To not have this use MyISAM instead of InnoDB as storage engine

Perhaps (I haven't tested this) a solution is to set innodb_autoinc_lock_mode to 0.
According to http://dev.mysql.com/doc/refman/5.7/en/innodb-auto-increment-handling.html this might make things a bit slower (if you perform inserts of multiple rows in a single query) but should remove gaps.

You can try insert like :
insert ignore into table select (select max(id)+1 from table), "value1", "value2" ;
This will try
insert new data with last unused id (not autoincrement)
if in unique fields duplicate entry found ignore it
else insert new data normally
( but this method not support to update fields if duplicate entry found )

Position Autoincrement in Talend

So i a bit lost and don t really know how to hang up this one...
Consider that i have a 2 DB table in Talend, let say firstly
A table invoices_only which has as fields, the invoiceNummer and the authors like this
Then, a table invoices_table with the field (invoiceNummer, article, quantity and price) and for one invoice, I can have many articles, for example
and through a tmap want to obtain a table invoice_table_result, with new columns, one for the article position, an one other for the total price. for the position i know that i can use something like the Numeric.sequence("s1",1,1) function, but don t know how to restart my counter when a new invoices nummer is found, and of course for the total price it is just a basic multiplication
so my result should be some thing like this
Here is a draft of my talend job, i m doing a lookup on the invoicenummer between the table invoice_only and invoices
Any Advices? thanks.

A trick I use is to do the sequence like this:
Numeric.sequence("s" + row.InvoiceNummer, 1, 1)
This way, the sequence gets incremented while you're still on the same InvoiceNummer, and a new one is started whenever a new InvoiceNummer is found.

There are two ways to achieve it,
tJavaFlex
Sql
tJavaFlex
You can compare current data with the previous data and reset the sequence value using below function,
if () {
Numeric.resetSequence(seqName, startValue);
}
Sql
Once data is loaded into the tables, create a post job and use an update query to update the records. You have to select the records and take the rank of the values. On top of the select you have to perform the update.
select invoicenumber, row_number() over(partition by invoicenumber, order by invoicenumber) from table name where -- conditions if any.
Update statements vary with respect to the database, please provide which database are you using, so that can provide the update query.
I would recommend you to achieve this through Sql

Hibernate concurrency creating a duplicate record on saveOrUpdate

I'm trying to implement a counter with Java, Spring, Hibernate and Oracle SQL. Each record represents a count, by a given timestamp. Let's say each record is uniquely identified by the minute, and each record holds a count column. The service should expect to receive a ton of concurrent requests and my update a counter column for possibly the same record.
In my table, if the record does not exist, just insert the record in and set its count to 1. Otherwise, find the record by timestamp and increase its existing counter column by 1.
In order to ensure that we're maintain data consistency and integrity, I'm using pessimistic locking. For example, if 20 counts come in at the same time, and not necessarily by the same user, it's possible that we may override the record from a stale read of that record before updating. With locking, I'm ensuring that if 20 counts come in, the net effect on the database should represent the 20 count.
So locking is fine, but the problem is that if the record never did exist in the first place, and we have two or more concurrent requests coming in trying to update the not-yet-existant record, I've observed that the a duplicate record gets inserted because we cannot lock on a record that doesn't exist yet. How can we ensure that no duplicates get created in the table? Should it be controlled via Oracle? Or can I manage this via my app and Hibernate?
Thank you.

One was to avoid this sort of problem altogether would be to just generate the count at the time you actually query the data. Oracle has an analytic function ROW_NUMBER() which can assign a row number to each record in the result set of a query. As a rough example, consider the following query:
SELECT
ts,
ROW_NUMBER() OVER (ORDER BY ts) rn
FROM yourTable
The count you want would be in the rn column, representing the number of records appearing since the first entry in the table. Of course, you could further restrict the query.
This approach is robust to removing records, as the count would always start with 1. One drawback is that row number functionality is not supported by Hibernate. You would have to run this either as a native query or a stored proc.

Get identity after Instead of insert trigger

I am using Hibernate with MSSQL server writing the software that integrates with an existing database. There is an instead of insert trigger on the table that I need to insert into and it messes up ##Identity, which means on Hibernate's save I can't get the id of inserted row. I can't control the trigger (can't modify it). I saw this question, but it involves procedures, which my trigger does not have, so I thought my question is different enough. I can't post the whole trigger, but hopefully I can post enough to get the point across:
CREATE TRIGGER TrigName ON TableName
INSTEAD OF INSERT
AS
SET XACT_ABORT ON
BEGIN TRANSACTION
-- several DECLARE, SET statements
-- a couple of inserts into other tables for business logic
-- plain T-SQL statements without procedures or functions
...
-- this is the actual insert that i need to perform
-- to be honest, I don't quite understand how INSERTED table
-- was filled with all necessary columns by this point, but for now
-- I accept it as is (I am no SQL pro...)
INSERT INTO ClientTable (<columns>)
SELECT <same columns> from INSERTED
-- a couple of UPDATE queries to unrelated tables
...
COMMIT TRANSACTION;
I was wondering if there is a reliable way to get the id of the row being inserted? One solution I thought of and tried to make is to install an on insert trigger on the same table that writes the newly inserted row into a new table I added to the db. I'd use that table as a queue. After transaction commit in Hibernate I could go into that table and run a select with the info I just inserted (I still have access to it from the same method scope), and I can get the id and finally remove that row. This is a bulky solution, but best I can come up with so far.
Would really appreciate some help. I can't modify existing triggers and procedures, but I can add something to the db if it absolutely does not affect existing logic (like that new table and a on insert trigger).
To sum up: I need to find a way to get the ID of the row I just inserted with Hibernate's save call. Because of that instead of insert trigger, hibernate always returns identity=0. I need to find a way to get that ID because I need to do the insert in a few other tables during one transaction.

I think I found an answer for my question. To reply to #SeanLange's comment: I can't actually edit insert code - it's done by another application and inquiry to change that will take too long (or won't happen - it's a legacy application). What I did is insert another trigger on insert on the same table. Since I know the order of operations in the existing instead of insert trigger I can see that the last insert operation will be in the table I want so that means my on insert trigger will fire right after that. In the scope of that trigger I have access to inserted table out of which I pull out the id.
CREATE TRIGGER Client_OnInsert ON myClientTable
FOR INSERT
AS
BEGIN
DECLARE #ID int;
SET #ID = (select ClientID from inserted);
INSERT INTO ModClient (modClientId)
OUTPUT #ID
VALUES (#ID);
END
GO
Then in Hibernate (since I can't use save() anymore), I use a NativeQuery to do this insert. I set parameters and run the list() method of NativeQuery, which returns a List where the first and only argument is the id I want.
This is a bulky way, I know. If there is anything that's really bad that will stand out to people - please let me know. I would really appreciate some feedback on this. However, I wanted to post this answer as a potential answer that worked so far, but it does not mean it's very good. For this solution to work I did have to create another small table ModClient, which I will have to use as a temp id storage for this exact purpose.

Insert fail then update OR Load and then decide if insert or update

I have a webservice in java that receives a list of information to be inserted or updated in a database. I don't know which one is to insert or update.
Which one is the best approach to abtain better performance results:
Iterate over the list(a object list, with the table pk on it), try to insert the entry on Database. If the insert failed, run a update
Try to load the entry from database. if the results retrieved update, if not insert the entry.
another option? tell me about it :)
In first calls, i believe that most of the entries will be new bd entries, but there will be a saturation point that most of the entries will be to update.
I'm talking about a DB table that could reach over 100 million entries in a mature form.
What will be your approach? Performance is my most important goal.

If your database supports MERGE, I would have thought that was most efficient (and treats all the data as a single set).
See:
http://www.oracle.com/technology/products/oracle9i/daily/Aug24.html
https://web.archive.org/web/1/http://blogs.techrepublic%2ecom%2ecom/datacenter/?p=194

If performance is your goal then first get rid of the word iterate from your vocabulary! learn to do things in sets.
If you need to update or insert, always do the update first. Otherwise it is easy to find yourself updating the record you just inserted by accident. If you are doing this it helps to have an identifier you can look at to see if the record exists. If the identifier exists, then do the update otherwise do the insert.

The important thing is to understand the balance or ratio between the number of inserts versus the number of updates on the list you receive. IMHO you should implement an abstract strategy that says "persists this on database". Then create concrete strategies that (for example):
checks for primary key, if zero records are found does the insert, else updates
Does the update and, if fails, does the insert.
others
And then pull the strategy to use (the class fully qualified name for example) from a configuration file. This way you can switch from one strategy to another easily. If it is feasible, could be depending on your domain, you can put an heuristic that selects the best strategy based on the input entities on the set.

MySQL supports this:
INSERT INTO foo
SET bar='baz', howmanybars=1
ON DUPLICATE KEY UPDATE howmanybars=howmanybars+1

Option 2 is not going to be the most efficient. The database will already be making this check for you when you do the actual insert or update in order to enforce the primary key. By making this check yourself you are incurring the overhead of a table lookup twice as well as an extra round trip from your Java code. Choose which case is the most likely and code optimistically.
Expanding on option 1, you can use a stored procedure to handle the insert/update. This example with PostgreSQL syntax assumes the insert is the normal case.
CREATE FUNCTION insert_or_update(_id INTEGER, _col1 INTEGER) RETURNS void
AS $$
BEGIN
INSERT INTO
my_table (id, col1)
SELECT
_id, _col1;
EXCEPTION WHEN unique_violation THEN
UPDATE
my_table
SET
col1 = _col1
WHERE
id = _id;
END;
END;
$$
LANGUAGE plpgsql;
You could also make the update the normal case and then check the number of rows affected by the update statement to determine if the row is actually new and you need to do an insert.
As alluded to in some other answers, the most efficient way to handle this operation is in one batch:
Take all of the rows passed to the web service and bulk insert them into a temporary table
Update rows in the mater table from the temp table
Insert new rows in the master table from the temp table
Dispose of the temp table
The type of temporary table to use and most efficient way to manage it will depend on the database you are using.