Subject: Identity column data type difference in PostgreSQL and Oracle

From: Muhammad Ikram <[email-masked]>
Date: Fri, 3 May 2024 15:57:53 +0500

Hello,

Tables which have an identity column in Oracle when migrated to PostgreSQL,
the data type of Identity column is changed to bigint from number by the
tools. This causes the size of column to be reduced to max value supported
by bigint which is way lower than the oracle  number max.
Secondly one has to change referencing columns data type as well.

What should be a better strategy for such transformations ?

Sample tables

CREATE TABLE Sales (
    *transaction_id* NUMBER GENERATED ALWAYS AS IDENTITY MINVALUE 1
MAXVALUE <maxvaluefornumberdatatype> INCREMENT BY 1 START WITH 1  NOCYCLE
    customer VARCHAR2(100),
    transaction_date DATE,
    store_id NUMBER
);

CREATE TABLE Sales_Details (
    *transaction_id* NUMBER,
    item VARCHAR2(100),
    quantity NUMBER,
    price NUMBER,
    CONSTRAINT fk_transaction_id FOREIGN KEY (transaction_id) REFERENCES
Sales(transaction_id)
);

--
Regards,
Muhammad Ikram

---

From: Peter Eisentraut <[email-masked]>
Date: Fri, 3 May 2024 13:09:41 +0200

On 03.05.24 12:57, Muhammad Ikram wrote:
> Tables which have an identity column in Oracle when migrated to 
> PostgreSQL, the data type of Identity column is changed to bigint from 
> number by the tools. This causes the size of column to be reduced to max 
> value supported by bigint which is way lower than the oracle  number max.

Sequences in PostgreSQL are limited to bigint, there is nothing that can 
be changed about that.  But you are approximately the first person to 
complain that the range of ids provided by bigint is too small, so maybe 
it's worth reconsidering whether it would work for you.  If it really is 
too small, maybe a uuid would work.  But yes, you'll need to make some 
adjustments to the rest of your database or application code if you make 
such changes.