[bitnami/postgresql] Introduces environment variable POSTGRESQL_DEFAULT_TRANSACTION_ISOLATION to change the global default transaction isolation level

[cowclaw]

Description of the change

The change introduces a new environment variable POSTGRESQL_DEFAULT_TRANSACTION_ISOLATION to the bitnami postgres images. The environment variable can be used to change the global default for the transaction isolation level in postgresql.

The change fixes #25013

It's currently not possible to change the default transaction isolation level using the POSTGRESQL_EXTRA_FLAGS if the desired isolation level's name contains a space.

containers/bitnami/postgresql/15/debian-11/rootfs/opt/bitnami/scripts/postgresql/run.sh

Lines 19 to 22 in 218f537

	if [[ -n "${POSTGRESQL_EXTRA_FLAGS:-}" ]]; then
	read -r -a extra_flags <<< "$POSTGRESQL_EXTRA_FLAGS"
	flags+=("${extra_flags[@]}")
	fi

If we'd omit the -r flag given to read in it would work with escaping the space in "repeatable read" with a backslash (repeatable\ read). However that this is not possible to preserve backwards compatibility since it could break existing solutions.

Benefits

It preserves backwards compatibility but still offers a possibility to change the global default transaction isolation level.

Possible drawbacks

It does not use the existing environment variable POSTGRESQL_EXTRA_FLAGS.

Applicable issues

--

Additional information

I verified the change is correct using the below method.

For each folder in

• bitnami/postgresql/11/debian-11/
• bitnami/postgresql/12/debian-11/
• bitnami/postgresql/13/debian-11/
• bitnami/postgresql/14/debian-11/
• bitnami/postgresql/15/debian-11/

do

docker build -t postgres_tmp .

docker run -eALLOW_EMPTY_PASSWORD=yes --rm --name postgresql postgres_tmp
echo "SELECT current_setting('transaction_isolation');" | docker exec -i postgresql psql postgres postgres 

 current_setting 
-----------------
 read committed
(1 row)

docker run -ePOSTGRESQL_DEFAULT_TRANSACTION_ISOLATION="repeatable read" -eALLOW_EMPTY_PASSWORD=yes --rm --name postgresql postgres_tmp 
echo "SELECT current_setting('transaction_isolation');" | docker exec -i postgresql psql postgres postgres 

 current_setting 
-----------------
 repeatable read
(1 row)

[rafariossaa]

Hi,
Thanks for adding this.
This new environment variable should be also added to postgresql-env.sh

[cowclaw]

Hi @rafariossaa

Thanks for the review.

I updated postgresql-env.sh in df9866a

[rafariossaa]

LGTM

[rafariossaa]

LGTM