Bug 1827445: Check if a table column exists in a quicker way

Without needing to create the xmldb table / field objects

We do this by trying to query the column and capture the SQLException
if it doesn't exist

behatnotneeded

Change-Id: I0a15dd4d1d4e47e6650576c084ee9e1d36b4ae62
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>

htdocs/lib/dml.php

@@ -1970,3 +1970,17 @@ function get_db_version() {
     }
     return $version;
 }
+
+function db_column_exists($table, $field) {
+    global $DB_IGNORE_SQL_EXCEPTIONS;
+    // We will check to see if a column exists by seeing if it throws an error or not
+    try {
+        $DB_IGNORE_SQL_EXCEPTIONS = true;
+        get_column_sql("SELECT " . db_quote_identifier($field) . " FROM " . db_table_name($table) . " LIMIT 1");
+        $DB_IGNORE_SQL_EXCEPTIONS = false;
+        return true;
+    }
+    catch (SQLException $e) {
+        return false;
+    }
+}

htdocs/lib/user.php

@@ -1883,12 +1883,8 @@ function load_user_institutions($userid) {
     }
     $userid = (int) $userid;
 
-    require_once('ddl.php');
-    $table = new XMLDBTable('institution');
-    $field = new XMLDBField('logoxs');
-    $logoxs = field_exists($table, $field) ? ',i.logoxs' : '';
-    $field = new XMLDBField('tags');
-    $tags = field_exists($table, $field) ? ',i.tags' : '';
+    $logoxs = db_column_exists('institution', 'logoxs') ? ',i.logoxs' : '';
+    $tags = db_column_exists('institution', 'tags') ? ',i.tags' : '';
     if ($userid !== 0 && $institutions = get_records_sql_assoc('
         SELECT u.institution, ' . db_format_tsfield('ctime') . ',' . db_format_tsfield('u.expiry', 'membership_expiry') . ',
                u.studentid, u.staff, u.admin, i.displayname, i.theme, i.registerallowed, i.showonlineusers,

htdocs/lib/view.php

@@ -1576,10 +1576,7 @@ class View {
 
                 if (array_search($accessrecord, $accessdata_added) === false) {
                     $accessrecord->view = $this->get('id');
-                    require_once('ddl.php');
-                    $table = new XMLDBTable('view_access');
-                    $field = new XMLDBField('id');
-                    if (field_exists($table, $field)) {
+                    if (db_column_exists('view_access', 'id')) {
                         $vaid = insert_record('view_access', $accessrecord, 'id', true);
                         handle_event('updateviewaccess', array(
                             'id' => $vaid,

htdocs/lib/web.php

@@ -1305,10 +1305,7 @@ class Theme {
             return get_config('wwwroot') . 'thumb.php?type=logobyid&id=' . $this->headerlogosmall;
         }
         else {
-            require_once('ddl.php');
-            $table = new XMLDBTable('institution');
-            $field = new XMLDBField('logoxs');
-            if (field_exists($table, $field) && $sitelogocustomsmallid = get_field('institution', 'logoxs', 'name', 'mahara')) {
+            if (db_column_exists('institution', 'logoxs') && $sitelogocustomsmallid = get_field('institution', 'logoxs', 'name', 'mahara')) {
                 return get_config('wwwroot') . 'thumb.php?type=logobyid&id=' . $sitelogocustomsmallid;
             }
         }