feat: Add the check to make the downgrade not possible

Author: ZPascal

README.md

@@ -76,7 +76,7 @@ The complete list of available properties can be found in the [spec](jobs/postgr
 
 Property | Description
 -------- | -------------
-databases.version | Define the used PostgreSQL major version. Default: 15
+databases.version | Define the used PostgreSQL major version. Default: 16
 databases.port | The database port. Default: 5432
 databases.databases | A list of databases and associated properties to create when Postgres starts
 databases.databases[n].name | Database name

jobs/postgres/spec

@@ -46,7 +46,7 @@ provides:
 properties:
   databases.version:
     description: "The database version e.g. 11, 13, 15 or 16"
-    default: "16"
+    default: 16
   databases.port:
     description: "The database port"
     default: 5432

jobs/postgres/templates/utils.sh.erb

@@ -68,6 +68,13 @@ function is_major() {
   [ "${pgversion_current%.*}" != "${pgversion_upgrade_from%.*}" ]
 }
 
+function check_postgresql_versions(){
+    if [[ $(echo -e "$pgversion_upgrade_from\n$pgversion_current" | sort --version-sort | head --lines=1) != $pgversion_upgrade_from ]]; then
+        echo "The downgrade of the database instance is not supported."
+        exit 1
+    fi
+}
+
 function init_data_dir(){
   if [ ! -f "${DATA_DIR}/postgresql.conf" ]; then
     # initdb creates data directories
@@ -77,7 +84,7 @@ function init_data_dir(){
 }
 
 function run_major_upgrade(){
-  if is_major; then
+  if is_major && check_postgresql_versions; then
     rm -rf ${DATA_DIR_PREVIOUS}
     echo "Running a PostgreSQL major upgrade from ${pgversion_upgrade_from} to ${pgversion_current}"
     touch "$POSTGRES_UPGRADE_LOCK"
@@ -105,7 +112,7 @@ EOF
   fi
 }
 function run_minor_upgrade(){
-  if ! is_major; then
+  if ! is_major && check_postgresql_versions; then
     rm -rf ${DATA_DIR_PREVIOUS}
     echo "Running a PostgreSQL minor upgrade from ${pgversion_upgrade_from} to ${pgversion_current}"
     <% if p("databases.skip_data_copy_in_minor") %>

test/test_major_or_minor_version.sh

@@ -5,10 +5,18 @@ pgversion_current=$2
 # From postgres-x.y.z, it's major if x and y are not the same
 # in $pgversion_current and $pgversion_upgrade_from
 
+function check_postgresql_versions(){
+    if [[ $(echo -e "$pgversion_upgrade_from\n$pgversion_current" | sort --version-sort | head --lines=1) != $pgversion_upgrade_from ]]; then
+        echo "The downgrade of the database instance is not supported."
+        exit 1
+    fi
+}
+
 function is_major() {
   [ "${pgversion_current%.*}" != "${pgversion_upgrade_from%.*}" ]
 }
-if is_major; then
+
+if is_major && check_postgresql_versions; then
  echo is major
 else
  echo is minor