Re: Adding a stored generated column without long-lived locks

Hi,

I tested v10 of the patch on the latest PostgreSQL master.
The patch applied cleanly, and PostgreSQL built successfully. git diff
--check completed without any issues.
I also ran: make check and all regression tests passed.
For the main functionality, I created a table with 100,000 existing
rows, backfilled the column, and added the required CHECK constraint:
CHECK (generated_value IS NOT DISTINCT FROM id * 2)
The following command then completed successfully:
ALTER TABLE test_gen_v10
ALTER COLUMN generated_value
ADD GENERATED USING CONSTRAINT test_gen_v10_check STORED;

The column was confirmed as: generated always as (id * 2) stored
I also tested the conversion with a table containing 1,000,000 rows.
The relation file path and size remained unchanged before and after
the conversion:
Before:
filepath: base/5/16393
size: 44,285,952 bytes (42 MB)

After:
filepath: base/5/16393
size: 44,285,952 bytes (42 MB)

This indicates that the table was not physically rewritten during the
conversion.
Overall, the v10 patch worked as expected in my testing.

Regards,
solai