Set minimum install MySQL version to be 5.5 and a recommended minimum of 5.7

Fix to use min install version

CRM/Upgrade/Incremental/General.php

@@ -44,6 +44,20 @@ class CRM_Upgrade_Incremental_General {
    */
   const MIN_INSTALL_PHP_VER = '7.1.0';
 
+  /**
+   * The minimum recommended MySQL/MariaDB version.
+   *
+   * A site running an earlier version will be told to upgrade.
+   */
+  const MIN_RECOMMENDED_MYSQL_VER = '5.7';
+
+  /**
+   * The minimum MySQL/MariaDB version required to install Civi.
+   *
+   * @see install/index.php
+   */
+  const MIN_INSTALL_MYSQL_VER = '5.5';
+
   /**
    * Compute any messages which should be displayed before upgrade.
    *

CRM/Utils/Check/Component/Env.php

@@ -938,12 +938,14 @@ class CRM_Utils_Check_Component_Env extends CRM_Utils_Check_Component {
   public function checkMysqlVersion() {
     $messages = [];
     $version = CRM_Utils_SQL::getDatabaseVersion();
-    if (version_compare(CRM_Utils_SQL::getDatabaseVersion(), '5.7', '<')) {
+    $minInstallVersion = CRM_Upgrade_Incremental_General::MIN_INSTALL_MYSQL_VER;
+    $minRecommendedVersion = CRM_Upgrade_Incremental_General::MIN_RECOMMENDED_MYSQL_VER;
+    if (version_compare(CRM_Utils_SQL::getDatabaseVersion(), $minInstallVersion, '<')) {
       $messages[] = new CRM_Utils_Check_Message(
         __FUNCTION__,
         ts('This system uses MySQL/MariaDB version %1. To ensure the continued operation of CiviCRM, upgrade your server now. At least MySQL version %2 or MariaDB version %3 is recommended', [
           1 => $version,
-          2 => '5.7',
+          2 => $minRecommendedVersion,
           3 => '10.1',
         ]),
         ts('MySQL Out of date'),
@@ -951,6 +953,7 @@ class CRM_Utils_Check_Component_Env extends CRM_Utils_Check_Component {
         'fa-server'
       );
     }
+    return $messages;
   }
 
 }

Civi/Install/Requirements.php

@@ -291,7 +291,7 @@ class Requirements {
    * @return array
    */
   public function checkMysqlVersion(array $db_config) {
-    $min = '5.1';
+    $min = CRM_Upgrade_Incremental_General::MIN_INSTALL_MYSQL_VER;
     $results = [
       'title' => 'CiviCRM MySQL Version',
       'severity' => $this::REQUIREMENT_OK,

install/index.php

@@ -480,11 +480,11 @@ class InstallRequirements {
         )
       )
       ) {
-        @$this->requireMySQLVersion("5.1",
+        @$this->requireMySQLVersion(CRM_Upgrade_Incremental_General::MIN_INSTALL_MYSQL_VER,
           array(
             ts("MySQL %1 Configuration", array(1 => $dbName)),
-            ts("MySQL version at least %1", array(1 => '5.1')),
-            ts("MySQL version %1 or higher is required, you are running MySQL %2.", array(1 => '5.1', 2 => mysqli_get_server_info($this->conn))),
+            ts("MySQL version at least %1", array(1 => CRM_Upgrade_Incremental_General::MIN_INSTALL_MYSQL_VER)),
+            ts("MySQL version %1 or higher is required, you are running MySQL %2.", array(1 => CRM_Upgrade_Incremental_General::MIN_INSTALL_MYSQL_VER, 2 => mysqli_get_server_info($this->conn))),
             ts("MySQL %1", array(1 => mysqli_get_server_info($this->conn))),
           )
         );