ROWID columns
Informix®
When creating a table, Informix automatically adds a
ROWID integer column (applies to non-fragmented tables only).
The ROWID column is auto-filled with a unique number and can be used like a
primary key to access a given row.
Informix ROWID usage was a
common practice in the early days of Informix
4GL programming. Today it is recommended to define all your database tables with a
PRIMARY KEY to uniquely identify rows.
With Informix, the sqlca.sqlerrd[6]
register contains the ROWID of the last row affected by an INSERT,
UPDATE or DELETE statement.
PostgreSQL
Before PostgreSQL 12, OID columns (similar to Informix ROWID columns) were available. Starting
with PostgreSQL version 12, OID columns are no longer supported.
PostgreSQL tables have a CTID system column, but the value of this column defines the storage location of the row, the value changes when updating.
Solution
Starting with PostgreSQL 12, user-table OIDs are no longer supported. Consequently, Informix ROWID columns cannot be emulated.
As a general SQL programming pattern, get rid of ROWID usage and use PRIMARY KEY
columns to identify database table rows.