Add max_locks_per_transaction config option (#718)

Signed-off-by: Marcelo Henrique Neppel <marcelo.neppel@canonical.com>

Author: marceloneppel

config.yaml

@@ -17,6 +17,14 @@ options:
       “pg_catalog.english”.
     type: string
     default: "pg_catalog.simple"
+  instance_max_locks_per_transaction:
+    description: |
+      Specifies the maximum amount of memory to be used by maintenance operations,
+      such as "VACUUM", "CREATE INDEX", and "ALTER TABLE ADD FOREIGN KEY".
+      If this value is specified without units, it is taken as kilobytes.
+      Allowed values are: from 64 to 2147483647.
+    type: int
+    default: 64
   instance_password_encryption:
     description: |
       Determines the algorithm to use to encrypt the password.

src/config.py

@@ -20,6 +20,7 @@ class CharmConfig(BaseConfigModel):
 
     durability_synchronous_commit: str | None
     instance_default_text_search_config: str | None
+    instance_max_locks_per_transaction: int | None
     instance_password_encryption: str | None
     logging_log_connections: bool | None
     logging_log_disconnections: bool | None
@@ -131,6 +132,15 @@ def instance_password_encryption_values(cls, value: str) -> str | None:
 
         return value
 
+    @validator("instance_max_locks_per_transaction")
+    @classmethod
+    def instance_max_locks_per_transaction_values(cls, value: int) -> int | None:
+        """Check instance_max_locks_per_transaction config option is between 64 and 2147483647."""
+        if value < 64 or value > 2147483647:
+            raise ValueError("Value is not between 64 and 2147483647")
+
+        return value
+
     @validator("logging_log_min_duration_statement")
     @classmethod
     def logging_log_min_duration_statement_values(cls, value: int) -> int | None:

tests/integration/test_config.py

@@ -37,6 +37,9 @@ async def test_config_parameters(ops_test: OpsTest) -> None:
         {
             "durability_synchronous_commit": [test_string, "on"]
         },  # config option is one of `on`, `remote_apply` or `remote_write`
+        {
+            "instance_max_locks_per_transaction": ["-1", "64"]
+        },  # config option is between 64 and 2147483647
         {
             "instance_password_encryption": [test_string, "scram-sha-256"]
         },  # config option is one of `md5` or `scram-sha-256`